**3. Phenotypic profile and functional features of neutrophil granulocytes**

The study of the subpopulations of NG presents a new approach to the determination of functional activity of NG, allowing to assess the adequacy of the inclusion of NG in the implementation of the immune response, as well as to diagnose and predict the outcome of the disease. It is known that various phenotypic profiles and the level of equipment with surface receptors are associated with morphological features and determine the functional potential of NG-cytokine production, transendothelial migration, intracellular and extracellular killing, and formation of NET [7–9]. The existence of a sufficiently large number of NG subpopulations with different possibilities is demonstrated. NGs that receive complex cytokine influences not only acquire new features but also undergo different stages of activation and differentiation while expressing MHCII antigens, CD80, CD86, ICAM-1, and LFA-1 [7, 10, 11]. It has been shown that inducing cytokine stimuli differentiates NG in a unique hybrid subpopulation with dual phenotypic and functional properties characteristic of both NG and dendritic cells (DC) involved in innate and adaptive immune responses [12]. We have identified in our earlier works the following subpopulations of NG: regulatory; suppressor; pro-inflammatory, initiating inflammatory reaction; inflammatory with a positive microbicidal potential (antibacterial, antiviral, antifungal); inflammatory with negative cytotoxic potential, "aggressive"; anti-inflammatory, regulating inflammation regression; antineoplastic, TAN1; and pro-tumor, TAN2 and hybrid [13]. Phagocytic and microbicidal function and virucidal activity of NG are directly dependent on phenotypic features: the number and density of such expressed receptors as CD11b/CD18, CD10, CD15, CD16, CD32, CD64, CD35, etc. [6]. Expression on NG membrane of CD32 and CD16 is important

*Neutrophils*

surface.

**2. Neutrophil granulocyte receptors**

the presence of subpopulations with different immunological roles. The use of monoclonal antibodies made it possible to confirm the existence of NG subpopulations using phenotypic characteristics. In 1998, the first nomenclature of human neutrophils antigens (HNAs) was created on the basis of membrane-expressed glycoprotein groups: HNA-1 (FcγRIIIb, CD16), HNA-2 (CD177), HNA-3 (CTL2), HNA-4 (CD11b/CD18, Mac-1, CR3), and HNA-5 (CD11a/CD18) [1]. The concept of heterogeneity of NG was discussed by scientists for more than 20 years and was confirmed with the accumulation of evidence on the presence of subsets of NG with various functions both in healthy subjects and in various diseases. Various methods have been used to detect the subpopulations of NG, such as cell maturity, functional activity, and localization, including receptors or markers of the cell

Cell populations and subpopulations of NG show a high degree of plasticity and functional heterogeneity depending on the characteristics of the course of physiological or pathological scenarios of the immune response, which, first of all, is due to potent receptor equipment. The membrane complex of NG expresses adhesion molecules, receptors for different ligands: cytokines, immunoglobulins, other cell membrane molecules, etc. NGs are capable to express MHC-1, selectins (CD62L), selectin receptors (CD162 (PSGL-1)), integrins (CD18 (β2-integrin), CD11a (LFA-1), CD11b (CR3), CD11c (CR4), CD11d), integrin receptors (ICAM receptors for β2-integrins - ICAM-1 (CD50), ICAM-3 (CD54). NG expresses receptors for chemoattractants (PFPR and FPLR for fMLP), receptors for chemokines (CXCR1, CXC2, CCR1), FcR receptors (CD16 (FcγRIII), CD32 (FcγRII), CD64 (FcγRI), CD89 (FcαRI), FcεR), receptors for complement components (CR1 (CD35), CR3 (CD11b), CR4 (CD11c), C5aR, C3aR, C5L2), receptor for LPS and endotoxins (CD14), cell adhesion receptor (CD15). NG receptors are involved in binding bacteria, in angiogenesis and apoptosis (CD17), in cell proliferation and differentiation (CD24), in PAMP recognition (TLR 1, 2, 4-10; NOD - receptors). In addition, on NG membrane there is a costimulatory receptor for B- lymphocytes (CD28), apoptosis activation/induction receptor (CD95), IL-2 receptor (CD25), which is NG activation marker; there are also molecules that determine the ability of NG to be APC (CD40, CD80, CD86, MHC II). NGs have multiple receptors for cytokines (IL-8, TNFα, IL-1, IL-2, IL-15, IL-17, IFNα, IFNγ, G-CSF, GM-CSF, etc.), hormones, neuropeptides, histamine, and kinases. The recently revealed expression of TCR-like (TCRL, TCRαβ) receptors on NG membrane, present throughout the life of a person and decreasing in old age, opens up new, previously

unknown immune mechanisms for the functioning of NG [2] (**Figure 1**).

NGs are equipped with receptors that recognize endogenous molecules of "danger" alarms or danger-associated molecular patterns (DAMPs)—extracellular ATP, fragments of the extracellular matrix, heat shock proteins, nucleic acids (DNA and RNA fragments of its own cells), nuclear protein HMGB-1, and others—through which activation of the cell takes place and its inclusion in the inflammation reaction [3]. It has been established that the initiation of apoptosis of NG in clinically healthy individuals is under the influence of TNFα, sTRAIL, and IL-4 ligand [4]. Recently, new ways of activating the NG signal via ITAM/Syk-CARD9 have been described in the interaction of β-glycans with dectin-1, which triggers the synthesis of the cytokine IL-23 inducing the formation of Th17 cells [5]. NG receptor pool is located on intracellular membrane of secretory vesicles, gelatinase and specific granules, these receptors are translocated to surface membrane of NG only under the action of inducing stimuli [6]. Thus, the membrane expression of NG not only reflects the

**44**

in the realization of phagocytic function and antibody-dependent cellular cytotoxicity (ADCC), which is associated with CD11b-/CD18-dependent enhancement of adhesion, degranulation, and killing [14]. CD64, CD32, and CD16 are triggering molecules that induce immune phagocytosis and killing processes [15].

The variants of remodeling of NG phenotype simultaneously expressing functionally significant receptors CD64, CD32, CD11b, and CD16 in patients with infectious and inflammatory diseases, including newborns of different gestational ages [15], patients with neoplastic processes [10, 16], women of reproductive age with genital and extragenital infectious-inflammatory diseases [17] have great diagnostic and prognostic significance. When we study the variability of the simultaneous presentation of NG receptors CD64, CD32, CD16, and CD11b on the membrane, it was established that in healthy adults and children of different ages in the peripheral blood, there is one major subpopulation of CD64<sup>−</sup>CD32+ CD16+ CD11b+ and five minor subpopulations of NG, CD64<sup>−</sup>CD32+ CD16+ CD11b<sup>−</sup>, CD64<sup>−</sup> CD32<sup>−</sup> CD16+ CD11b+ , CD64+ CD32+ CD16+ CD11b+ , CD64+ CD32+ CD16+ CD11b<sup>−</sup> , and CD64+ CD32<sup>−</sup>CD16+ CD11b+ , with different equipment and density of studied receptors. We detected a significant increase in NG subpopulation with CD64+ CD32+ CD16+ CD11b+ phenotype with a high expression density of CD11b and CD16 in newborns with infectious and inflammatory diseases of bacterial etiology (congenital pneumonia, neonatal sepsis) (**Figure 2**).

The observed increase in this subpopulation of NG in the peripheral blood is directly related to the severity of the infectious-inflammatory process: the more clinically severe the disease, the greater the number of NG with this phenotype CD64<sup>+</sup> CD32+ CD16+ CD11b+ is in circulation [18]. In fertile age women with genital and extragenital infectious and inflammatory diseases planning pregnancy, the phenotypic variability of NG—the appearance of a subpopulation of CD16<sup>+</sup> CD32+ CD11b—was also revealed, which indicates a persistent violation of their receptor function and the need for its adequate correction consisting in restoring the phenotypic composition of NG. Thus, the provision of pre-gravity training with the inclusion of immunotherapy has a positive clinical and immunological effect, which consists in normalizing the receptor function of NG, which

#### **Figure 2.**

*Phenotypic profiles of CD64+ CD32+ CD16+ CD11b+ NG in children with congenital pneumonia and neonatal sepsis.*

**47**

**Table 1.**

*I.V. et al., 2010–2016).*

*Remodeling of Phenotype CD16+*

CD64<sup>−</sup>CD32<sup>−</sup>CD16+

Healthy adults and children

Purulent-septic diseases in children and adults

Acute bacterial infection in adults

Respiratory and herpes infections in

Acute EBV infection

children

in adults

*DOI: http://dx.doi.org/10.5772/intechopen.81631*

CD11b+

tion phenotype according to their studies (**Table 1**).

CD64<sup>−</sup>CD32+

CD64+

CD16brightCD11bdim CD62LbrightCD63dim CD62LdimCD63dim (1:1)

CD32+

CD62LdimCD63mid CD62LdimCD63dim

CD64<sup>−</sup>CD16+

*CD11b+*

correlates with an increase in the percentage of women who become pregnant [17]. The obtained data allow us to develop criteria for monitoring the course of associated viral infections and bacterial pro-inflammatory diseases, to diagnose and/or predict the aggravation of their severity, and to optimize immunotherapy methods aimed at correcting NG dysfunction. Multiple increases in the subpopulation of

respiratory viral infections associated with herpesviral mono- or mixed infection. There was a significant replicative activity of herpesviruses such as HSV I/HSV II, CMV, EBV, and HHV VI [18, 19]. In addition, authors of this article put together all information into the table for the period from 2010 to 2016, about NG subpopula-

Specific NG subpopulation composition and also adequate level of corresponding surface membrane marker expression density is important for the proper NG function. Thus, Pillay et al. found several subpopulations of NG with different phenotypes, which differed in the number and density of equipment with receptors: mature NG with the phenotype CD16highCD62Lhigh, immature NG with the phenotype CD16lowCD62Lhigh, suppressive NG with the phenotype CD16highCD62Llow, and NG precursors with the phenotype CD16lowCD62Llow [11]. Circulating NG subpopulation with the phenotype CD16lowCD62Lhigh was observed in children with respiratory syncytial viral infection, as well as in viral and bacterial coinfection

**Group Subpopulation Functions/diagnostic significance**

CD11b+

CD11b+

activity

process

CD16dimCD11bbright -Marker of acute process of the bacterial infection

circulation)

infection

CD16brightCD11bbright - Marker of severity of viral infection process

infection

circulation)

*Neutrophilic granulocyte subpopulation phenotypes and their function and diagnostic significance (Nesterova* 

CD32<sup>−</sup>CD11b+ -Prognostic sign of adverse course of viral

herpetic infection

microbicidal activity

CD16+

CD16+

 *Neutrophilic Granulocytes in Acute Viral and Acute…*

NG have been shown in children with repeated acute










*Remodeling of Phenotype CD16<sup>+</sup> CD11b+ Neutrophilic Granulocytes in Acute Viral and Acute… DOI: http://dx.doi.org/10.5772/intechopen.81631*

correlates with an increase in the percentage of women who become pregnant [17]. The obtained data allow us to develop criteria for monitoring the course of associated viral infections and bacterial pro-inflammatory diseases, to diagnose and/or predict the aggravation of their severity, and to optimize immunotherapy methods aimed at correcting NG dysfunction. Multiple increases in the subpopulation of CD64<sup>−</sup>CD32<sup>−</sup>CD16+ CD11b+ NG have been shown in children with repeated acute respiratory viral infections associated with herpesviral mono- or mixed infection. There was a significant replicative activity of herpesviruses such as HSV I/HSV II, CMV, EBV, and HHV VI [18, 19]. In addition, authors of this article put together all information into the table for the period from 2010 to 2016, about NG subpopulation phenotype according to their studies (**Table 1**).

Specific NG subpopulation composition and also adequate level of corresponding surface membrane marker expression density is important for the proper NG function. Thus, Pillay et al. found several subpopulations of NG with different phenotypes, which differed in the number and density of equipment with receptors: mature NG with the phenotype CD16highCD62Lhigh, immature NG with the phenotype CD16lowCD62Lhigh, suppressive NG with the phenotype CD16highCD62Llow, and NG precursors with the phenotype CD16lowCD62Llow [11]. Circulating NG subpopulation with the phenotype CD16lowCD62Lhigh was observed in children with respiratory syncytial viral infection, as well as in viral and bacterial coinfection


#### **Table 1.**

*Neutrophilic granulocyte subpopulation phenotypes and their function and diagnostic significance (Nesterova I.V. et al., 2010–2016).*

*Neutrophils*

CD64<sup>−</sup>

CD64+

CD64<sup>+</sup>

CD16<sup>+</sup>

and CD64+

CD32<sup>−</sup>

CD32+

CD32+

CD32+

CD16+

CD16+

CD16+

CD32<sup>−</sup>CD16+

in the realization of phagocytic function and antibody-dependent cellular cytotoxicity (ADCC), which is associated with CD11b-/CD18-dependent enhancement of adhesion, degranulation, and killing [14]. CD64, CD32, and CD16 are triggering

The variants of remodeling of NG phenotype simultaneously expressing functionally significant receptors CD64, CD32, CD11b, and CD16 in patients with infectious and inflammatory diseases, including newborns of different gestational ages [15], patients with neoplastic processes [10, 16], women of reproductive age with genital and extragenital infectious-inflammatory diseases [17] have great diagnostic and prognostic significance. When we study the variability of the simultaneous presentation of NG receptors CD64, CD32, CD16, and CD11b on the membrane, it was established that in healthy adults and children of different ages in the

CD16+

CD16+

CD16+

phenotype with a high expression density of CD11b and

 *NG in children with congenital pneumonia and* 

, CD64+

CD11b+

is in circulation [18]. In fertile age women with

, with different equipment and density of

CD11b<sup>−</sup>,

CD32+

CD11b+

CD11b<sup>−</sup> ,

molecules that induce immune phagocytosis and killing processes [15].

peripheral blood, there is one major subpopulation of CD64<sup>−</sup>CD32+

CD32+

studied receptors. We detected a significant increase in NG subpopulation with

CD16 in newborns with infectious and inflammatory diseases of bacterial etiology

The observed increase in this subpopulation of NG in the peripheral blood is directly related to the severity of the infectious-inflammatory process: the more clinically severe the disease, the greater the number of NG with this phenotype

CD11b—was also revealed, which indicates a persistent violation

genital and extragenital infectious and inflammatory diseases planning pregnancy, the phenotypic variability of NG—the appearance of a subpopulation of

of their receptor function and the need for its adequate correction consisting in restoring the phenotypic composition of NG. Thus, the provision of pre-gravity training with the inclusion of immunotherapy has a positive clinical and immunological effect, which consists in normalizing the receptor function of NG, which

CD16+

, CD64+

and five minor subpopulations of NG, CD64<sup>−</sup>CD32+

(congenital pneumonia, neonatal sepsis) (**Figure 2**).

CD11b+

CD11b+

CD11b+

CD11b+

**46**

**Figure 2.**

*neonatal sepsis.*

*Phenotypic profiles of CD64+*

*CD32+*

*CD16+*

*CD11b+*

[20, 21]. It is shown that the subpopulation of immature NG did not possess the ability to protect against microorganisms. Activated mature NG with immunosuppressive properties was found in patients with HIV infection [22]. Suppressive NG can cause paralysis of the immune system, as a result of which anti-infective protection is disrupted, which facilitates the occurrence of bacterial complications and the emergence of viral and bacterial coinfection [20, 23]. The appearance of CD16highCD62Llow NG significantly increases with bacterial infection or viral and bacterial coinfection, and at the same time, in the lower respiratory tract, in lungs this subpopulation is practically not detected in patients with viral infection [11, 20]. Neutrophilic subpopulation characterized by the phenotype CD16lowCD62Llow was observed in children with severe viral respiratory infection without bacterial coinfection and in patients with bacterial sepsis [20, 21]. Using flow cytometry in combination with a visual evaluation of cells, it was shown that a large number of myelocytes and metamyelocytes are included in this subpopulation, so NG with the phenotype CD16lowCD62Llow was called a subpopulation of NG precursors. A sequential increase in the number of NG precursors was statistically significant (p < 0.001) and did not depend on the presence of bacterial coinfection [20]. It was suggested that the NG precursors originate from a heterogeneous family of granulocyte myeloid-derived suppressor cells (G-MDSCs), which include granulocyte cells with the property of immune inhibition [20, 24]. Significant differences in the number of markers of activation and degranulation of CD11b, CD54, CD63, and CD66b in the above four subpopulations (mature NG, immature NG, suppressor NG, and NG "precursors") in viral infections and in bacterial coinfections in newborns with severe viral infection, practically, are not revealed. It was noted that the activation and degranulation of suppressor NG revealed a high level of expression of CD11b and CD63, whereas in NG "precursors," the highest level of expression of CD63 and CD66b and a low level of expression of CD11b and CD54 were observed [20]. Interestingly that NG number in the bloodstream equipped with CD62L on the surface membrane is larger than CD62L NG obtained from bronchoalveolar lavage, which is presumably associated with the loss of this receptor during migration. Pillay et al. [11, 24] discovered the existence of a new subpopulation CD11cbrightCD62LdimCD16brightCD11bbright NG—mature hypersegmented human NG with immunosuppressive activity. This subpopulation was able to suppress the proliferation of T cells through the release of active forms of the oxygenate and showed high expression of CD11b. Earlier studies by Woodfin A. and co-authors demonstrated that suppressive NGs—mature cells with hypersegmented nucleus, expressing high levels of ICAM-1—have the ability to reverse transendothelial migration (TEM) [25]. Later, Cortjens and his colleagues in 2017 [20] showed that in severe respiratory viral infection in infants, the expression of the activation marker CD11b was significantly increased in the suppressor subpopulation of NG. These suppressor subpopulations of NG, which appeared in viral and bacterial coinfections in newborns, also had the highest expression of CD63 molecules on surface membranes, which indicated active degranulation of NG.

## **4. Neutrophil granulocytes in infectious diseases**

Defective functioning NGs (deficiency of NG amount; violation of phagocytic function; deficiency of myeloperoxidase, defensins, lactoferrin, glucose-6 phosphate dehydrogenase, NADPH oxidase, etc.; defects in the formation of NET) do not provide adequate antimicrobial protection, which leads to the development of atypically occurring infectious and inflammatory diseases, sepsis, acute hematogenous osteomyelitis, recurrent purulent infections, chronic bacterial infections,

**49**

reaction syndrome [34].

*Remodeling of Phenotype CD16+*

*DOI: http://dx.doi.org/10.5772/intechopen.81631*

*CD11b+*

and in children especially in the neonatal period [29, 30].

Neonatal NG characterized qualitative and quantitative deficit compared to adult NG. Neonatal sepsis is a global problem because it has the most severe consequences and is characterized by high mortality. This occurs against the background of impairments in the functioning of the immune system and defective NG, which contributes to the rapid dissimilation of the infection and, as a result, to the death of the newborn [31]. Thus, three important violations of NG that contribute to the emergence of severe neonatal sepsis and septic shock are described: neutropenia, decreased plasticity, and delayed apoptosis [32]. In the case of sepsis or the syndrome of a systemic inflammatory reaction, a large number of immature forms of NG appear in circulation. NGs are characterized by a decrease in phagocytic functional activity, a decreased production of ROS, a defective expression level of CD14 receptors, and a violation of the migratory ability. Immature NGs are characterized by a high basal level of intracellular TNF-α/IL-10 ratio, which confirms their pro-inflammatory phenotype. They have a longer life cycle, are resistant to spontaneous apoptosis, and can mature ex vivo [33]. Patients with sepsis (a more severe inflammatory reaction) have a more pronounced decrease in some receptors, in particular TREM-1, which has a key role in amplifying the production of inflammatory cytokines than patients suffering from a noninfectious systemic inflammatory

NGs affect the adaptive immune response in viral infection [13, 22] through antigen presentation, translocation of pathogenic viruses to the lymph nodes, suppressor modulation of the T-cell response, and expression of Toll-like receptors recognizing the herpesvirus DNA (TLR-9) [35–37]. NGs are important elements of antiviral immunity, realizing their capabilities through the process of phagocytosis, the formation of active forms of oxygen (ROS), the formation of NET, and the ability to synthesize and secrete cytokines, defensins, and interferons [18, 38–40]. Recent studies have shown that on the one hand, NG can perform antiviral protection and on the other hand, many viruses, in particular herpesviruses, can

etc. Adequate response of NG in contact with various aggressive pathogens (viruses, bacteria, fungi) can develop in different ways. At the same time, the lack of functional activity of NG is a risk factor for the development of many pathological conditions. Changes in both quantitative and functional characteristics of different subsets of NG are recorded in pathological conditions, that is, NG phenotype is transformed due to a multivariate change in the expression of various receptors. In this case, the defectiveness of microbicidal and regulatory functions of NG leads to a violation of antigen elimination and, as a result, to the aggravation of the course of acute or chronic bacterial, viral, and fungal infections [13]. At present, various dysfunctions of NG are described, which can proceed according to different scenarios in patients with infectious diseases with atypical current: (1) hypofunction and NG deficiency in recurrent and persistent-relapsing purulent processes and chronic infectious diseases, viral and bacterial etiology, not amenable to standard treatment; (2) blockade of functional activity of NG, manifested by the development of an inadequate response up to the state of non-response in chronic sluggish infectious and inflammatory processes with a protracted course of exacerbations in socially significant infections and sepsis; and (3) hyperfunctioning of NG (e.g., extracellular production of oxygen radicals in a high concentration), which can lead to suppression of the T cells and other members of the immune system and damage different organs and tissues in chronic immune-dependent diseases or septic shock [26–28]. Atypically occurring infectious and inflammatory diseases against the background of immune system disorders, and, in particular, against the background of NG dysfunction, lead to increased morbidity, partial and sometimes complete loss of ability to work, and high lethality in sepsis, both in adult subjects

 *Neutrophilic Granulocytes in Acute Viral and Acute…*

#### *Remodeling of Phenotype CD16<sup>+</sup> CD11b+ Neutrophilic Granulocytes in Acute Viral and Acute… DOI: http://dx.doi.org/10.5772/intechopen.81631*

etc. Adequate response of NG in contact with various aggressive pathogens (viruses, bacteria, fungi) can develop in different ways. At the same time, the lack of functional activity of NG is a risk factor for the development of many pathological conditions. Changes in both quantitative and functional characteristics of different subsets of NG are recorded in pathological conditions, that is, NG phenotype is transformed due to a multivariate change in the expression of various receptors. In this case, the defectiveness of microbicidal and regulatory functions of NG leads to a violation of antigen elimination and, as a result, to the aggravation of the course of acute or chronic bacterial, viral, and fungal infections [13]. At present, various dysfunctions of NG are described, which can proceed according to different scenarios in patients with infectious diseases with atypical current: (1) hypofunction and NG deficiency in recurrent and persistent-relapsing purulent processes and chronic infectious diseases, viral and bacterial etiology, not amenable to standard treatment; (2) blockade of functional activity of NG, manifested by the development of an inadequate response up to the state of non-response in chronic sluggish infectious and inflammatory processes with a protracted course of exacerbations in socially significant infections and sepsis; and (3) hyperfunctioning of NG (e.g., extracellular production of oxygen radicals in a high concentration), which can lead to suppression of the T cells and other members of the immune system and damage different organs and tissues in chronic immune-dependent diseases or septic shock [26–28]. Atypically occurring infectious and inflammatory diseases against the background of immune system disorders, and, in particular, against the background of NG dysfunction, lead to increased morbidity, partial and sometimes complete loss of ability to work, and high lethality in sepsis, both in adult subjects and in children especially in the neonatal period [29, 30].

Neonatal NG characterized qualitative and quantitative deficit compared to adult NG. Neonatal sepsis is a global problem because it has the most severe consequences and is characterized by high mortality. This occurs against the background of impairments in the functioning of the immune system and defective NG, which contributes to the rapid dissimilation of the infection and, as a result, to the death of the newborn [31]. Thus, three important violations of NG that contribute to the emergence of severe neonatal sepsis and septic shock are described: neutropenia, decreased plasticity, and delayed apoptosis [32]. In the case of sepsis or the syndrome of a systemic inflammatory reaction, a large number of immature forms of NG appear in circulation. NGs are characterized by a decrease in phagocytic functional activity, a decreased production of ROS, a defective expression level of CD14 receptors, and a violation of the migratory ability. Immature NGs are characterized by a high basal level of intracellular TNF-α/IL-10 ratio, which confirms their pro-inflammatory phenotype. They have a longer life cycle, are resistant to spontaneous apoptosis, and can mature ex vivo [33]. Patients with sepsis (a more severe inflammatory reaction) have a more pronounced decrease in some receptors, in particular TREM-1, which has a key role in amplifying the production of inflammatory cytokines than patients suffering from a noninfectious systemic inflammatory reaction syndrome [34].

NGs affect the adaptive immune response in viral infection [13, 22] through antigen presentation, translocation of pathogenic viruses to the lymph nodes, suppressor modulation of the T-cell response, and expression of Toll-like receptors recognizing the herpesvirus DNA (TLR-9) [35–37]. NGs are important elements of antiviral immunity, realizing their capabilities through the process of phagocytosis, the formation of active forms of oxygen (ROS), the formation of NET, and the ability to synthesize and secrete cytokines, defensins, and interferons [18, 38–40]. Recent studies have shown that on the one hand, NG can perform antiviral protection and on the other hand, many viruses, in particular herpesviruses, can

*Neutrophils*

[20, 21]. It is shown that the subpopulation of immature NG did not possess the ability to protect against microorganisms. Activated mature NG with immunosuppressive properties was found in patients with HIV infection [22]. Suppressive NG can cause paralysis of the immune system, as a result of which anti-infective protection is disrupted, which facilitates the occurrence of bacterial complications and the emergence of viral and bacterial coinfection [20, 23]. The appearance of CD16highCD62Llow NG significantly increases with bacterial infection or viral and bacterial coinfection, and at the same time, in the lower respiratory tract, in lungs this subpopulation is practically not detected in patients with viral infection [11, 20]. Neutrophilic subpopulation characterized by the phenotype CD16lowCD62Llow was observed in children with severe viral respiratory infection without bacterial coinfection and in patients with bacterial sepsis [20, 21]. Using flow cytometry in combination with a visual evaluation of cells, it was shown that a large number of myelocytes and metamyelocytes are included in this subpopulation, so NG with the phenotype CD16lowCD62Llow was called a subpopulation of NG precursors. A sequential increase in the number of NG precursors was statistically significant (p < 0.001) and did not depend on the presence of bacterial coinfection [20]. It was suggested that the NG precursors originate from a heterogeneous family of granulocyte myeloid-derived suppressor cells (G-MDSCs), which include granulocyte cells with the property of immune inhibition [20, 24]. Significant differences in the number of markers of activation and degranulation of CD11b, CD54, CD63, and CD66b in the above four subpopulations (mature NG, immature NG, suppressor NG, and NG "precursors") in viral infections and in bacterial coinfections in newborns with severe viral infection, practically, are not revealed. It was noted that the activation and degranulation of suppressor NG revealed a high level of expression of CD11b and CD63, whereas in NG "precursors," the highest level of expression of CD63 and CD66b and a low level of expression of CD11b and CD54 were observed [20]. Interestingly that NG number in the bloodstream equipped with CD62L on the surface membrane is larger than CD62L NG obtained from bronchoalveolar lavage, which is presumably associated with the loss of this receptor during migration. Pillay et al. [11, 24] discovered the existence of a new subpopulation CD11cbrightCD62LdimCD16brightCD11bbright NG—mature hypersegmented human NG with immunosuppressive activity. This subpopulation was able to suppress the proliferation of T cells through the release of active forms of the oxygenate and showed high expression of CD11b. Earlier studies by Woodfin A. and co-authors demonstrated that suppressive NGs—mature cells with hypersegmented nucleus, expressing high levels of ICAM-1—have the ability to reverse transendothelial migration (TEM) [25]. Later, Cortjens and his colleagues in 2017 [20] showed that in severe respiratory viral infection in infants, the expression of the activation marker CD11b was significantly increased in the suppressor subpopulation of NG. These suppressor subpopulations of NG, which appeared in viral and bacterial coinfections in newborns, also had the highest expression of CD63 molecules on

surface membranes, which indicated active degranulation of NG.

Defective functioning NGs (deficiency of NG amount; violation of phagocytic

phosphate dehydrogenase, NADPH oxidase, etc.; defects in the formation of NET) do not provide adequate antimicrobial protection, which leads to the development of atypically occurring infectious and inflammatory diseases, sepsis, acute hematogenous osteomyelitis, recurrent purulent infections, chronic bacterial infections,

function; deficiency of myeloperoxidase, defensins, lactoferrin, glucose-6-

**4. Neutrophil granulocytes in infectious diseases**

**48**

negatively affect the function of the NG, transform their phenotype, and influence the formation of populations/subpopulations with different functional properties [22]. Herpes viruses block NG antiviral activity, increase NG apoptosis, which leads to neutropenia. Damage to the NG by herpesviruses disrupts their functioning and leads in combination with other factors to disruption of adaptation reactions [13, 22, 36, 41, 42]. In recent years, it has been shown that in chronic herpesviral infection, there are numerous subpopulations of the NG, characterized by different phenotypes with different receptor equipment, possessing different functional properties: the ability to restructure chromatin, express cytokine genes and secrete cytokines, realize the activity of the granular apparatus, produce active oxygen species, and form NET and cytotoxicity.

#### **4.1 CD16+ CD11b+ phenotype of neutrophilic granulocytes in acute viral and acute bacterial infections**

The first reports of the heterogeneity of CD16 expression (FcγIII) on NG membrane (induces oxidative burst and phagocytosis) appeared more than 25 years ago [25, 43, 44], but only recently the mechanisms and functional consequences of this heterogeneity have been studied. In particular we have identified different CD16+ CD11b+ NG phenotypes with individual characteristics in patients with acute viral (acute viral Epstein-Barr (EBV) infection) and acute bacterial infectious-inflammatory diseases (acute bacterial tonsillitis) [45]. Summarizing the obtained data, it should be noted that in healthy subjects, CD16brightCD11bdimNG subpopulation was major. The NG of this subpopulation in trace amounts was detected with acute viral infection and was completely absent in acute bacterial infection. In acute viral infection, the number of NGs of a highly equipped subpopulation—CD16brightCD11bbrightNG—significantly increased, whereas in acute bacterial infection, there was a significantly lower increase in the number of NGs of this subpopulation. At the same time, in healthy individuals the subpopulation of CD16brightCD11bbrightNG was minor. In the case of acute bacterial infection, the CD16dimCD11bbright NG subpopulation, which was absent in conditionally healthy individuals, became dominant, and in the case of acute viral infection, it appeared in an insignificant amount. Subpopulation CD16dimCD11bdim was detected only in healthy individuals (**Figure 3**).

**51**

acute bacterial infections.

**ODN2395 on CD16+**

**bacterial infection**

*Remodeling of Phenotype CD16+*

*DOI: http://dx.doi.org/10.5772/intechopen.81631*

*CD11b+*

CD11b-dependent increase in adhesion and degranulation [14].

processes of other localizations; however, this requires further study.

ics of presentation of CD16 and CD11b membrane receptors in the CD16+

**4.2 Evaluation of the effects of the sodium salt of eukaryotic DNA and** 

**CD11b+**

NG population in healthy individuals and acute inflammation in the region of the lymphopharynx ring reflects the differentiated response of NG to acute viral and

The use of drugs to improve the accuracy of exposure to target cells and selectively trigger the type of effector reaction is currently considered topical;

**NG phenotype in patients with acute viral and** 

The clinical picture of many infectious diseases of viral or bacterial etiology in the early stages of the disease can proceed according to a similar scenario. In this case, when verifying the diagnosis of an acute infectious process of viral or bacterial etiology, there are often certain difficulties that prevent timely proper selection of etiotropic therapy. Conducting an express analysis that allows us to specify dominant NG subpopulation—CD16brightCD11bbright or CD16dimCD11bbright can contribute to the differential diagnosis of acute viral and acute bacterial processes of the lymphogenous ring, which will allow timely optimization of etiotropic therapy. On the other hand, it is possible that the evaluation of these subpopulations of NG can be used for early differential diagnosis of various acute viral and acute bacterial

Thus, CD16brightCD11bdim NG subpopulations prevail in healthy subjects from 80 and up to 99.9%. In acute viral infection of the lymphogenous ring—infectious mononucleosis associated with EBV—the predominance of the subpopulation CD16brightCD11bbrightNG is detected in an amount of 40% or more. In acute bacterial infection of the lymphatic pharynx, a subpopulation CD16dimCD11bbright NG predominates—from 40% and higher. The observed phenomenon of different dynam-

CD11b+

Apparently, this is a reserve nonactivated pool of circulating NG, since it is known that in the resting state, the NG is insignificantly equipped with membranes CD16 and CD11b. It should be noted that there are certain difficulties and differences in interpreting the data concerning the reasons for the low equipment of the NG CD16 receptor. Thus, early works of Elghetany M. T. (2002) [6] states that, in inflammation, the expression level of CD16 decreases and explain this phenomenon by shading this receptor; then Elghetany and Lacombe note that surface antigen expression of granulocytes depends on age, sex, race, and the presence of stress [46]. Pillay et al. [24] noted the appearance of a "paradoxical" NG population of low-membrane CD16-CD16dim NG in the experiment with the introduction of LPS in vivo. The authors linked this phenomenon to the release of immature forms of granulocytes in the blood, reinforcing this conclusion with morphological studies: CD16dimNG demonstrates the morphology of "young" band nuclear NG [47]. Thus, it is possible that the appearance of the prevalent major population of CD16dimCD11bbright in the acute bacterial infection of the pharyngeal lymphoid ring in patients in a state of moderate severity or with a severe condition is associated with the release of immature forms of the NG into circulation, which is a stereotype response of the NG in severe bacterial infection. The predominant subpopulation of CD16brightCD11bbrightNG in patients with acute viral infection has a high cytotoxic antiviral potential due to the high level of CD16 and CD11b expression. According to Kushner and Cheung [48], the detectable enhanced expression of CD16 on NG in a viral infection may be due to the greater functional significance of cytotoxic NGs expressing FcγRIII (CD16) for the implementation of ADCC associated with

 *Neutrophilic Granulocytes in Acute Viral and Acute…*

#### **Figure 3.**

*Phenotypic profiles of CD16+ CD11b+ NG in acute viral (AEBVI) and acute bacterial (ABT) infections.*

#### *Remodeling of Phenotype CD16<sup>+</sup> CD11b+ Neutrophilic Granulocytes in Acute Viral and Acute… DOI: http://dx.doi.org/10.5772/intechopen.81631*

Apparently, this is a reserve nonactivated pool of circulating NG, since it is known that in the resting state, the NG is insignificantly equipped with membranes CD16 and CD11b. It should be noted that there are certain difficulties and differences in interpreting the data concerning the reasons for the low equipment of the NG CD16 receptor. Thus, early works of Elghetany M. T. (2002) [6] states that, in inflammation, the expression level of CD16 decreases and explain this phenomenon by shading this receptor; then Elghetany and Lacombe note that surface antigen expression of granulocytes depends on age, sex, race, and the presence of stress [46]. Pillay et al. [24] noted the appearance of a "paradoxical" NG population of low-membrane CD16-CD16dim NG in the experiment with the introduction of LPS in vivo. The authors linked this phenomenon to the release of immature forms of granulocytes in the blood, reinforcing this conclusion with morphological studies: CD16dimNG demonstrates the morphology of "young" band nuclear NG [47]. Thus, it is possible that the appearance of the prevalent major population of CD16dimCD11bbright in the acute bacterial infection of the pharyngeal lymphoid ring in patients in a state of moderate severity or with a severe condition is associated with the release of immature forms of the NG into circulation, which is a stereotype response of the NG in severe bacterial infection. The predominant subpopulation of CD16brightCD11bbrightNG in patients with acute viral infection has a high cytotoxic antiviral potential due to the high level of CD16 and CD11b expression. According to Kushner and Cheung [48], the detectable enhanced expression of CD16 on NG in a viral infection may be due to the greater functional significance of cytotoxic NGs expressing FcγRIII (CD16) for the implementation of ADCC associated with CD11b-dependent increase in adhesion and degranulation [14].

The clinical picture of many infectious diseases of viral or bacterial etiology in the early stages of the disease can proceed according to a similar scenario. In this case, when verifying the diagnosis of an acute infectious process of viral or bacterial etiology, there are often certain difficulties that prevent timely proper selection of etiotropic therapy. Conducting an express analysis that allows us to specify dominant NG subpopulation—CD16brightCD11bbright or CD16dimCD11bbright can contribute to the differential diagnosis of acute viral and acute bacterial processes of the lymphogenous ring, which will allow timely optimization of etiotropic therapy. On the other hand, it is possible that the evaluation of these subpopulations of NG can be used for early differential diagnosis of various acute viral and acute bacterial processes of other localizations; however, this requires further study.

Thus, CD16brightCD11bdim NG subpopulations prevail in healthy subjects from 80 and up to 99.9%. In acute viral infection of the lymphogenous ring—infectious mononucleosis associated with EBV—the predominance of the subpopulation CD16brightCD11bbrightNG is detected in an amount of 40% or more. In acute bacterial infection of the lymphatic pharynx, a subpopulation CD16dimCD11bbright NG predominates—from 40% and higher. The observed phenomenon of different dynamics of presentation of CD16 and CD11b membrane receptors in the CD16+ CD11b+ NG population in healthy individuals and acute inflammation in the region of the lymphopharynx ring reflects the differentiated response of NG to acute viral and acute bacterial infections.

#### **4.2 Evaluation of the effects of the sodium salt of eukaryotic DNA and ODN2395 on CD16+ CD11b+ NG phenotype in patients with acute viral and bacterial infection**

The use of drugs to improve the accuracy of exposure to target cells and selectively trigger the type of effector reaction is currently considered topical;

*Neutrophils*

**4.1 CD16+**

ent CD16+

species, and form NET and cytotoxicity.

**CD11b+**

CD11b+

healthy individuals (**Figure 3**).

**acute bacterial infections**

negatively affect the function of the NG, transform their phenotype, and influence the formation of populations/subpopulations with different functional properties [22]. Herpes viruses block NG antiviral activity, increase NG apoptosis, which leads to neutropenia. Damage to the NG by herpesviruses disrupts their functioning and leads in combination with other factors to disruption of adaptation reactions [13, 22, 36, 41, 42]. In recent years, it has been shown that in chronic herpesviral infection, there are numerous subpopulations of the NG, characterized by different phenotypes with different receptor equipment, possessing different functional properties: the ability to restructure chromatin, express cytokine genes and secrete cytokines, realize the activity of the granular apparatus, produce active oxygen

The first reports of the heterogeneity of CD16 expression (FcγIII) on NG membrane (induces oxidative burst and phagocytosis) appeared more than 25 years ago [25, 43, 44], but only recently the mechanisms and functional consequences of this heterogeneity have been studied. In particular we have identified differ-

with acute viral (acute viral Epstein-Barr (EBV) infection) and acute bacterial infectious-inflammatory diseases (acute bacterial tonsillitis) [45]. Summarizing the obtained data, it should be noted that in healthy subjects, CD16brightCD11bdimNG subpopulation was major. The NG of this subpopulation in trace amounts was detected with acute viral infection and was completely absent in acute bacterial infection. In acute viral infection, the number of NGs of a highly equipped subpopulation—CD16brightCD11bbrightNG—significantly increased, whereas in acute bacterial infection, there was a significantly lower increase in the number of NGs of this subpopulation. At the same time, in healthy individuals the subpopulation of CD16brightCD11bbrightNG was minor. In the case of acute bacterial infection, the CD16dimCD11bbright NG subpopulation, which was absent in conditionally healthy individuals, became dominant, and in the case of acute viral infection, it appeared in an insignificant amount. Subpopulation CD16dimCD11bdim was detected only in

 **phenotype of neutrophilic granulocytes in acute viral and** 

NG phenotypes with individual characteristics in patients

*NG in acute viral (AEBVI) and acute bacterial (ABT)* 

**50**

**Figure 3.**

*infections.*

*Phenotypic profiles of CD16+*

*CD11b+*

in particular, the use of exogenous oligomers of RNA and DNA, in the process of metabolism of which nucleotides and deoxynucleotides are formed, is promising [49]. Nucleic acid preparations of immunomodulating action of various natures are widely used in practical medicine. Pharmacopoeial preparations are known: sodium nucleate (RNA derived from yeast) [50], sodium deoxyribonucleate (sodium salt of native DNA isolated from sturgeon fish milt) [51], and placentexintegro (DNA from trout milt) [52]. Now, the team of authors [49] showed that the substance of sodium deoxyribonucleate mainly contains short and medium DNA chains ending in the CpG motif. Recognition of CpG motifs by the immune system occurs through their interaction with the Toll-like receptor 9 (TLR9), which acts on the cells as "alarm," activating innate and acquired immunity and many times enhancing the body's response even to low-immunogenic antigens [53] with effects of increased proliferation, maturation, and secretion of a number of biologically active molecules—cytokines, costimulatory molecules, molecules of the main histocompatibility complex, etc. [51, 54]. Inflammation is directly related to neutrophilic granulocytes (NGs), which express almost all known TLRs [55], which explains their crucial role in the regulation of phagocytic cells. It should be noted that activation of TLR-4 induces e production of pro-inflammatory cytokines and chemokines (IL1β, IL8, TNFα), TLR-2 activation induces production of chemokine MCP-1, and synchronous activation of TLR-4 and TLR-9 is accompanied by a pronounced respiratory burst a change in the expression of NG adhesion molecules [56, 57]. In the current literature, there are data on the cooperation of TLR9 with the functionally significant receptor of phagocytes—CD11b in the process of recognition of pathogens, even at a low level of exposure to such pathogens [58]. CD11b is also known to both positively and negatively regulate TLR9-mediated mechanisms: control TLR9-triggered NK cell cytotoxicity and macrophage inflammatory responses [59, 60]. On the other hand, it was found that bacterial DNA enhances expression of CD11b genes, while TLR9 expression in NG does not change under the influence of bacterial DNA [61].

Comparative evaluation of the effect of in vitro sodium deoxyribonucleate and the TLR9 agonist (ODN2395) on CD16<sup>+</sup> CD11b+ subpopulation composition of NG in both healthy individuals and infectious diseases was of interest [62].

In particular, it was shown that when the peripheral blood of conventionally healthy volunteers with sodium deoxyribonucleate is incubated in vitro, the density of surface-localized CD11b and CD16 receptors is increased, which is expressed by a significant increase in the content of CD16brCD11bbrNG. The effect of the TLR9 agonist (ODN2395) on this subpopulation in patients with AEBVI allowed us to identify a tendency to decrease its relative content, the effects of the TLR9 agonist and sodium deoxyribonucleate did not affect the relative content of CD16brCD11bbrNH in patients with ABT (**Figures 4**–**6**).

The assessment of the content of the CD16brCD11bbrNG subpopulation in the incubation of the peripheral blood of patients with acute viral and acute bacterial processes made it possible to reveal a significant immunomodulating effect only in the experiment with sodium deoxyribonucleate. When the blood of patients with AEBVI was incubated, a significant decrease in the initially high relative content of CD16brCD11bbrNG was found.

In acute bacterial infection (ABT), there was an increase in the percentage of CD16brCD11bdimNG and a decrease in the initially predominant subpopulation of CD16dimCD11bdimNG (as in incubation with sodium deoxyribonucleate and with the TLR9 agonist), whereas in acute EBV infection, an increase in CD16brCD11bdimNG was observed under the influence of sodium deoxyribonucleate in vitro (**Figure 4**).

**53**

**Figure 6.**

*the subpopulation of CD16<sup>+</sup>*

*Remodeling of Phenotype CD16+*

**Figure 4.**

**Figure 5.**

*the subpopulation composition of CD16+*

*the subpopulation of CD16<sup>+</sup>*

*DOI: http://dx.doi.org/10.5772/intechopen.81631*

*CD11b+*

*CD11b+*

*Comparative analysis of the effect of the TLR9 agonist and sodium deoxyribonucleate in vitro on* 

*NG of healthy volunteers.*

*Comparative analysis of the effect of the TLR9 agonist and sodium deoxyribonucleate in vitro on* 

*NG in patients with ABT.*

*CD11b+*

It is important to note that the redistribution of NG subpopulation composition occurring under the action of both agonist and, especially, sodium deoxyribonucleate has a modulating nature, which suggests the involvement of Toll-like type 9 receptors in the regulation of functional NG activity in infectious processes.

*NG in patients with acute EBV infection.*

*Comparative analysis of the effect of the TLR9 agonist and sodium deoxyribonucleate in vitro on* 

*CD11b+*

 *Neutrophilic Granulocytes in Acute Viral and Acute…*

*Remodeling of Phenotype CD16<sup>+</sup> CD11b+ Neutrophilic Granulocytes in Acute Viral and Acute… DOI: http://dx.doi.org/10.5772/intechopen.81631*

#### **Figure 4.**

*Neutrophils*

DNA [61].

the TLR9 agonist (ODN2395) on CD16<sup>+</sup>

CD16brCD11bbrNG was found.

ate in vitro (**Figure 4**).

in particular, the use of exogenous oligomers of RNA and DNA, in the process of metabolism of which nucleotides and deoxynucleotides are formed, is promising [49]. Nucleic acid preparations of immunomodulating action of various natures are widely used in practical medicine. Pharmacopoeial preparations are known: sodium nucleate (RNA derived from yeast) [50], sodium deoxyribonucleate (sodium salt of native DNA isolated from sturgeon fish milt) [51], and placentexintegro (DNA from trout milt) [52]. Now, the team of authors [49] showed that the substance of sodium deoxyribonucleate mainly contains short and medium DNA chains ending in the CpG motif. Recognition of CpG motifs by the immune system occurs through their interaction with the Toll-like receptor 9 (TLR9), which acts on the cells as "alarm," activating innate and acquired immunity and many times enhancing the body's response even to low-immunogenic antigens [53] with effects of increased proliferation, maturation, and secretion of a number of biologically active molecules—cytokines, costimulatory molecules, molecules of the main histocompatibility complex, etc. [51, 54]. Inflammation is directly related to neutrophilic granulocytes (NGs), which express almost all known TLRs [55], which explains their crucial role in the regulation of phagocytic cells. It should be noted that activation of TLR-4 induces e production of pro-inflammatory cytokines and chemokines (IL1β, IL8, TNFα), TLR-2 activation induces production of chemokine MCP-1, and synchronous activation of TLR-4 and TLR-9 is accompanied by a pronounced respiratory burst a change in the expression of NG adhesion molecules [56, 57]. In the current literature, there are data on the cooperation of TLR9 with the functionally significant receptor of phagocytes—CD11b in the process of recognition of pathogens, even at a low level of exposure to such pathogens [58]. CD11b is also known to both positively and negatively regulate TLR9-mediated mechanisms: control TLR9-triggered NK cell cytotoxicity and macrophage inflammatory responses [59, 60]. On the other hand, it was found that bacterial DNA enhances expression of CD11b genes, while TLR9 expression in NG does not change under the influence of bacterial

Comparative evaluation of the effect of in vitro sodium deoxyribonucleate and

CD11b+

In particular, it was shown that when the peripheral blood of conventionally healthy volunteers with sodium deoxyribonucleate is incubated in vitro, the density of surface-localized CD11b and CD16 receptors is increased, which is expressed by a significant increase in the content of CD16brCD11bbrNG. The effect of the TLR9 agonist (ODN2395) on this subpopulation in patients with AEBVI allowed us to identify a tendency to decrease its relative content, the effects of the TLR9 agonist and sodium deoxyribonucleate did not affect the relative content of

The assessment of the content of the CD16brCD11bbrNG subpopulation in the incubation of the peripheral blood of patients with acute viral and acute bacterial processes made it possible to reveal a significant immunomodulating effect only in the experiment with sodium deoxyribonucleate. When the blood of patients with AEBVI was incubated, a significant decrease in the initially high relative content of

In acute bacterial infection (ABT), there was an increase in the percentage of CD16brCD11bdimNG and a decrease in the initially predominant subpopulation of CD16dimCD11bdimNG (as in incubation with sodium deoxyribonucleate and with the TLR9 agonist), whereas in acute EBV infection, an increase in CD16brCD11bdimNG was observed under the influence of sodium deoxyribonucle-

both healthy individuals and infectious diseases was of interest [62].

CD16brCD11bbrNH in patients with ABT (**Figures 4**–**6**).

subpopulation composition of NG in

**52**

*Comparative analysis of the effect of the TLR9 agonist and sodium deoxyribonucleate in vitro on the subpopulation of CD16<sup>+</sup> CD11b+ NG of healthy volunteers.*

#### **Figure 5.**

*Comparative analysis of the effect of the TLR9 agonist and sodium deoxyribonucleate in vitro on the subpopulation composition of CD16+ CD11b+ NG in patients with ABT.*

#### **Figure 6.**

*Comparative analysis of the effect of the TLR9 agonist and sodium deoxyribonucleate in vitro on the subpopulation of CD16<sup>+</sup> CD11b+ NG in patients with acute EBV infection.*

It is important to note that the redistribution of NG subpopulation composition occurring under the action of both agonist and, especially, sodium deoxyribonucleate has a modulating nature, which suggests the involvement of Toll-like type 9 receptors in the regulation of functional NG activity in infectious processes.

## **5. Conclusion**

The classical view of the NG, as short-lived finally differentiated cells, which carry out only phagocytosis, killing, and elimination of extracellular pathogens, is convincingly refuted by numerous recent studies. New scientific facts obtained during the last 10–15 years have demonstrated that NGs possess certain regulatory influences of activating, modulating, and suppressive nature, practically on all cells, both innate and adaptive immunity. The development of new diagnostic technologies allowed us to expand and deepen our understanding of the role of the NG in immune homeostasis and to evaluate the dynamic interrelation of the functional potential of the cell with gene expression and phenotypic polarization of the NG in response to inducing signals of intra- and extracellular environment. It is important to note that, to date, not all NG subpopulations have been identified.

Today it is well known that the population of CD16<sup>+</sup> CD11b<sup>+</sup> NG plays an important role in the reactions of phagocytosis and ADCC in infectious processes of various natures. It is also known that CD11b and CD16 NG are the most important triggers inducing the cascade of activation and regulatory processes of the NG. The resting unactivated NGs express the low levels of CD11b and CD16 membrane molecules. After activation additional translocation of intracellular CD16 and CD11b molecules to the NG membrane takes place [6, 36, 63]. Our studies showed that the subpopulation CD16brightCD11bdimNG prevailed in healthy people, and the NG with the phenotype CD16brightCD11bbright was absent in healthy volunteers but appeared and dominated in patients with acute EBV infection. It has been established that CD16brightCD11bdimNG subpopulation predominates in healthy individuals, subpopulation CD16brightCD11bbrightNG prevails in patients with acute viral infection, and CD16dimCD11bbrightNG subpopulation dominates in patients with acute bacterial infection. Identified by us in acute bacterial infection (acute bacterial tonsillitis), emergence of the prevalent population of CD16dimCD11bbright NG indicated, in our opinion, the release into circulation of immature forms of NG in a bacterial attack. At the same time, CD16brightCD11bbright NG subpopulation predominated in patients with acute viral infection (acute EBV infection). We hypothesized that on the one hand, the appearance of CD16brightCD11bbright NG with high cytotoxicity (high levels of CD16 expression) and with a suppressive effect on T-cell proliferation (high levels of CD11b molecules) is necessary for the implementation of antiviral activity of the NG in their fight against EBV infection. CD16brightCD11bbrightNG should have high antiviral activity. On the other hand, their suppressor properties (high levels of CD11b expression) may lead to various complications in the form of secondary bacterial infections. Thus, in severe acute EBV infection, we revealed the transformation of the NG phenotype and the appearance of a new subpopulation of CD16brightCD11bbrightNG with high cytotoxicity and suppressive effects. Further studies are needed to determine the functional significance of the CD16brightCD11bbright NG subpopulation for both EBV infection and other herpesvirus infections. In addition, early diagnosis of the etiological factors that cause an acute infectious process of a viral or bacterial nature is extremely important for the appointment of early etiopathogenetic therapy. The results of the present study demonstrate that the determination of various subpopulations of the NG in the early stages of an acute infectious process can contribute to the early differentiation of an acute viral process in which the CD16brightCD11bbright NG subpopulation dominates and the acute bacterial process dominated by the CD16dimCD11bbright NG subpopulation. On the other hand, it is extremely important to search for new substances that have immunomodulatory effects on the "negatively transformed" phenotype of the NG with the possibility of positive remodeling, which can prevent the attachment of serious complications, both in viral and bacterial infections [63].

**55**

**Author details**

provided the original work is properly cited.

*Remodeling of Phenotype CD16+*

viral and bacterial etiologies.

**Conflict of interest**

*DOI: http://dx.doi.org/10.5772/intechopen.81631*

*CD11b+*

Authors declare that there is no conflict of interest.

Our studies of the eukaryotic DNA sodium salt effect on the expression of functionally significant CD16 and CD11b NG receptors in healthy individuals and in infectious diseases of viral and bacterial etiology have demonstrated the potential for transformation of the negatively altered phenotype of the NG, in particular, by remodeling the expression of CD11b on the NG membrane [64]. The obtained data open certain prospects for the development of new therapeutic strategies that allow correcting the negatively transformed phenotype of various subpopulations of defective functioning NG in severe infectious and inflammatory processes, both

 *Neutrophilic Granulocytes in Acute Viral and Acute…*

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Irina V. Nesterova\*, Galina A. Chudilova, Svetlana V. Kovaleva,

Lyudmila V. Lomtatidze and Tatyana V. Rusinova Kuban State Medical University, Krasnodar, Russia

\*Address all correspondence to: inesterova1@yandex.ru

*Remodeling of Phenotype CD16<sup>+</sup> CD11b+ Neutrophilic Granulocytes in Acute Viral and Acute… DOI: http://dx.doi.org/10.5772/intechopen.81631*

Our studies of the eukaryotic DNA sodium salt effect on the expression of functionally significant CD16 and CD11b NG receptors in healthy individuals and in infectious diseases of viral and bacterial etiology have demonstrated the potential for transformation of the negatively altered phenotype of the NG, in particular, by remodeling the expression of CD11b on the NG membrane [64]. The obtained data open certain prospects for the development of new therapeutic strategies that allow correcting the negatively transformed phenotype of various subpopulations of defective functioning NG in severe infectious and inflammatory processes, both viral and bacterial etiologies.
