**2.3.2.2 Mast cell, eosinophil and its cellular contents**

Mast cells play a very important role in the pathogenesis of AD. Tryptase and chymase are the major compound of mast cell granules. They have various effects on angiotensin, metalloproteases, lipoproteins, procollagen, neuropeptides and cytokines. The study by Badertscher et al confirmed that mast cell chymase is increased in chronic atopic dermatitis lesion (Badertscher et al., 2005), while there was no correlation of serum tryptase level with the severity of AD (Gerdes et al., 2009).

Eosinophils play an important role in inflammatory process of AD, the activated eosinophils release granule proteins including eosinophil cationic protein (ECP) and eosinophil derived neurotoxin/eosinophil protein X (EDN/EPX). ECP is released from activated eosinophils during the inflammation process. Serum ECP level increased in children with AD (Badertscher et al., 2005; Damps-Konstanska et al., 2005), but there was no correlation with the SCORAD index (Wu et al., 2011). While a study by Selnes et al suggest that there is no association between serum ECP and AD in an unselected population of children (Selnes &Dotterud,2005).Several investigative evidence indicate that serum EDN may reflect the disease severity in childhood phase AD(Taniuchi et al., 2001; Lee et al.,2009) and correlated with SCORAD index (K.Y.Lee et al.,2009).

#### **2.3.2.3 T Lymphocytes and their subsets in peripheral blood**

For a long time, two main types of effector CD4+ T cells, named as type 1 T helper (Th1) and type 2 Th (Th2) respectively, have been thought to be deeply involved in AD. Th2 cells produce IL-4, IL-5 and IL-13, Th1 cells produce interferon (IFN)-γ as the main cytokines. AD is an inflammatory skin disease characterized by the predominant infiltration of T cells, eosinophils, mast cell, dendric cell (DC) and macrophages in lesions. Disequilibrium between Th1/Th2 lymphocytes is an important feature of AD. Typically, AD has been considered the paradigm of a Th2–mediated disease, characterized by increase of Th2 and decrease of Th1 and their cytokines level in peripheral blood. Recently, research efforts have resulted in new subgroups of CD4+ T cells, such as IL-17– producing Th cells (Th17), the main cytokine they produce is IL-17A, and T-regulatory (Treg) ( Agrawal et al., 2011; Souwer er al., 2010). There are two main groups of Treg cells identified. One is the natural Treg cells, characterized by CD4+CD25+ phenotype and develops under the control of the transcription factor FoxP3. The other is the adaptive Treg or T-regulatory type 1 (Tr1), characterized by the secretion of high levels of IL-10(M. Akdis et al., 2004; C.A.Akdis et al., 1998). It is suggested that the onset of allergic diseases are partly caused by insufficient development of allergen-specific Tregs. FoxP3+Treg could be found in the perivascular, dermis interstitial, and the dermoepidermal junction and the basal and suprabasal epidermal layers of AD (Caproni et al., 2007). But the study by Hayashida et al indicated that FoxP3+Treg subsets was similar to that of normal controls in peripheral blood of the acute phase AD and the decreased number of circulating Th17 cells is negatively correlated with CCL17, IgE and eosinophil levels in AD patients (Hayashida et al., 2011). IL-17 has been identified in acute AD lesions (Toda et al., 2003). The exact role of Treg and Th17 cell in AD is still unclear.

#### **2.3.2.4 Cytokines and chemokine in the serum**

A complex network of cytokines and chemokines are involved in atopic inflammation, at both the starting and maintainance stages of the inflammation. Scratching injury induce the production of proinflammatory cytokines (such as IL-1, TNF-α, GM-CSF), which in turn induce CCL27 and CCL17 development. Subsequently, CCL27 and CCL17 recruit skinhoming memory T cells into the skin. Within the skin, T cells are activated and release effector cytokines (eg, IL-4, IL-5, IL-13 in acute phase lesion, or IFN-r in the chronic lesion of AD ).These effector cytokines will sustain and amplify the production of chemokines within atopic skin. In this complex procedure, many chemokines, (such as CCL1, CCL2, CCL11, CCL13, CCL18, CCL20, CCL21, and CCL26) interact with various immune effector cells through their receptors(D.Y.Leung et al., 2004; Homey et al., 2006). AD is a disease with the participation of whole body immune system, and that the immunologic abnormality is not limited to the skin. Generally, as is widely accepted that AD has been considered the paradigm of a Th2–mediated disease, characterized by increase Th2 and decrease Th1 and cytokines level, elevated serum IgE levels, eosinophilia in peripheral blood. Recent researched showed that the severity of AD has also been found to be associated with the levels of various other cytokines and chemokines in the lesion and serum, in addition to the conventional serum parameters, such as total serum IgE (tIgE), eosinophilic cationic protein (ECP), increased T helper type 2 (Th2)-skewed cytokine patterns(IL4,13) and decreased IFNγ. Some of them in the serum of AD are correlated with disease severity, and thus may be new biomarkers to reflect AD disease severity. Clinical trials on interleukins and chemokines in the serum of patients with AD were summarized, in table1 and table 2.

#### **Interleukin/IL**

174 Atopic Dermatitis – Disease Etiology and Clinical Management

(C.A.Akdis et al., 2006). The remaining 20%–30% of patients exhibiting normal serum IgE levels and lack allergen-specific sensitization, are classified as intrinsic AD (IAD) (Novak &Bieber, 2003; Boguniewicz et al., 2006). 28% of AD serum contains IgE autoantibodies

For the total IgE and specific IgE, similar to skin tests, a negative result is fairly reliable in ruling out an IgE-mediated reaction. For a positive result, although the lesions significantly regress, there maybe no parallel decrease of serum IgE level. Further large-scale investigations of serum IgE levels between patients with extrinsic atopic dermatitis and

Mast cells play a very important role in the pathogenesis of AD. Tryptase and chymase are the major compound of mast cell granules. They have various effects on angiotensin, metalloproteases, lipoproteins, procollagen, neuropeptides and cytokines. The study by Badertscher et al confirmed that mast cell chymase is increased in chronic atopic dermatitis lesion (Badertscher et al., 2005), while there was no correlation of serum tryptase level with

Eosinophils play an important role in inflammatory process of AD, the activated eosinophils release granule proteins including eosinophil cationic protein (ECP) and eosinophil derived neurotoxin/eosinophil protein X (EDN/EPX). ECP is released from activated eosinophils during the inflammation process. Serum ECP level increased in children with AD (Badertscher et al., 2005; Damps-Konstanska et al., 2005), but there was no correlation with the SCORAD index (Wu et al., 2011). While a study by Selnes et al suggest that there is no association between serum ECP and AD in an unselected population of children (Selnes &Dotterud,2005).Several investigative evidence indicate that serum EDN may reflect the disease severity in childhood phase AD(Taniuchi et al., 2001; Lee et al.,2009) and correlated

For a long time, two main types of effector CD4+ T cells, named as type 1 T helper (Th1) and type 2 Th (Th2) respectively, have been thought to be deeply involved in AD. Th2 cells produce IL-4, IL-5 and IL-13, Th1 cells produce interferon (IFN)-γ as the main cytokines. AD is an inflammatory skin disease characterized by the predominant infiltration of T cells, eosinophils, mast cell, dendric cell (DC) and macrophages in lesions. Disequilibrium between Th1/Th2 lymphocytes is an important feature of AD. Typically, AD has been considered the paradigm of a Th2–mediated disease, characterized by increase of Th2 and decrease of Th1 and their cytokines level in peripheral blood. Recently, research efforts have resulted in new subgroups of CD4+ T cells, such as IL-17– producing Th cells (Th17), the main cytokine they produce is IL-17A, and T-regulatory (Treg) ( Agrawal et al., 2011; Souwer er al., 2010). There are two main groups of Treg cells identified. One is the natural Treg cells, characterized by CD4+CD25+ phenotype and develops under the control of the transcription factor FoxP3. The other is the adaptive Treg or T-regulatory type 1 (Tr1), characterized by the secretion of high levels of IL-10(M. Akdis et al., 2004; C.A.Akdis et al., 1998). It is suggested that the onset of allergic diseases are partly caused by insufficient development of allergen-specific Tregs. FoxP3+Treg could be found in the perivascular, dermis interstitial, and the dermoepidermal junction and the basal and suprabasal epidermal layers of AD (Caproni et al., 2007). But the study

which target keratinocytes in AD patients (Altrichter et al., 2008).

intrinsic atopic dermatitis are needed (Ott et al., 2009). **2.3.2.2 Mast cell, eosinophil and its cellular contents** 

the severity of AD (Gerdes et al., 2009).

with SCORAD index (K.Y.Lee et al.,2009).

**2.3.2.3 T Lymphocytes and their subsets in peripheral blood** 

Many interleukins participate in AD and it is a consensus that increased IL4, 13 levels are seen in the serum of AD. Recently, many of other interleukins have been shown to play roles in the pathogenesis of AD, and increased serum levels have been detected (in table1). IL-10 is a powerful Th2 cytokines produced by LC in the lesion of AD and exerts its function through inhibition of the secretion of Th1 cytokines. While, the level of IL-10 in the serum may be not a significant marker (Shin et al., 2005). IL-22, a member of the IL-10 family and known to be preferentially produced by Th17 cells, is increased and has significant correlation with CCL17 levels in the serum of AD patients (Hayashida et al., 2011). On the contrary, IL-12 is prominently expressed in the chronic lesion of AD, it is a powerful inducer of Th0 to Th1 conversion and subsequent IFN-γ secretion from Th1.The level of IL-12 in the serum of AD is controversially reported. Piancatelli et al confirmed the serum IL-12 levels increased in paediatric AD (Piancatelli et al., 2008), while the study by Aral, M et al showed that there was no statistically significant difference between children AD and controls in respect of serum levels of IL-12(Aral et al., 2006). IL-16 is a natural ligand of CD4 molecules. Besides its chemotactic properties to CD4-expressing cells, IL-16 amplifies inflammatory processes and possesses immunoregulatory functions (Mathy et al., 2000; Nagy et al., 2011). IL-16 was found to be increased in the serum of AD, both in child and adult patients (Nagy

Advances in Assessing the Severity of Atopic Dermatitis 177

Park et al.,

Aral et al.,

Sohn et al.,

Hon et al.,

Yoshizawa

Hayashida

Ezzat et al.,

Raap et al.,

**clinical parameters References Expressions in** 

2009

2009

T.F.Leung et al., 2003

<sup>2004</sup>Increase

<sup>2004</sup>Increase

<sup>2011</sup>Increase

<sup>2008</sup>Increase

et al., 2002 Increase Adult

et al., 2011 Increase Adults (mean±SD

**serum** 

Decrease under 10 years old

Decrease under 10 years old

No difference between mild and moderate

AD

**serum** 

2007 Increase 15±10 years;

<sup>2006</sup>Increase 5–12 year old

**Age of studied populations** 

range:2-41years

Age range, 9 months to 11 years; mean, 4.28±

2.8 years

Median age of 2.2 years (interquartile range 0.7-4.6 years)

(13–43years)

Ages ranged between 1 and 10 years (mean ± SD: 5.75 ± 2.11 years)

Extrinsic AD (mean age, 37.8±14.1 years); Intrinsic AD (mean age, 31.8±11.2 years)

age;27.2±6.1 years )

**Adult / childhood /infant phase** 

Children (mean age 11.4 years with moderate AD

Children (mean age 11.4 years with moderate AD

Median 2.1 years, range 0.6-4.2 years

**clinical parameters References Expression in** 

**Interleukins** 

**Correlation with other** 

Positive correlation with

Positive correlation with

Higher in sever AD than in

Positive correlation with

Positive correlation with eosinophil counts and serum

Positive correlation with LSS, SSS and SCORAD

Positive correlation with SCORAD index both in extrinsic AD and intrinsic

Table 1. Literatures about serum interleukins in AD

**Correlation with other** 

CXCL9 Not done Narbutt et al.,

IP-10 Not done Narbutt et al.,

Did not correlate with SCORAD index and its extend and intensity

soluble IL-2 receptor

IL-22 Positive correlation with

CCL17

index

AD

IL-31

**Chemokine** 

CXCL10/

SCORAD index

SCORAD index

SCORAD index

mild AD

et al., 2011; Belloni Fortina et al., 2006; Masuda et al., 2003).Also ,the level of IL-16 in the serum was significantly correlated with serum total IgE(Nagy et al., 2011), but not correlated with SCORAD index(Belloni Fortina et al., 2006) and eosinophils counting in peripheral blood(Nagy et al., 2011).The finding of Masuda K. et al confirmed IL-16 level in serum was significantly higher in patients with AD, and decreased significantly after topical treatment with corticosteroids or tacrolimus (Masuda et al., 2003). IL-18 is a pleiotropic cytokine that works both in Th1 and Th2 lymphocyte-mediated immunity. As a member of the IL-1 super family, IL-18 is a potent inducer of IFN-γ. IL-18 is involved in the pathogenesis of AD including Th1 and Th2 T lymphocyte-mediated immunity, including cytokine accumulation, and increase of IgE and histamine levels. Increased serum level of IL-18 and correlation with disease severity, eosinophil counts and serum sIL-2R levels was reported in several researches both in adult and children patients (Aral et al., 2006; Yoshizawa et al., 2002; Park &Youn, 2007; Sohn et al., 2004; Hon et al., 2004). IL-31 is a Th derived cytokine. Serum IL-31 was found over-expressed in both adults and paediatric AD and its serum level correlated positively with the disease severity (Raap et al., 2008; Ezzat et al., 2011).

#### **Chemokines their receptors**

Little is known about the very early events of atopic skin inflammation. The unceasing amplification inflammation cycle in AD lesions might start with pruritus and the injury induced by scratching, and skin barrier disruption, resulting in proinflammatory cytokine


et al., 2011; Belloni Fortina et al., 2006; Masuda et al., 2003).Also ,the level of IL-16 in the serum was significantly correlated with serum total IgE(Nagy et al., 2011), but not correlated with SCORAD index(Belloni Fortina et al., 2006) and eosinophils counting in peripheral blood(Nagy et al., 2011).The finding of Masuda K. et al confirmed IL-16 level in serum was significantly higher in patients with AD, and decreased significantly after topical treatment with corticosteroids or tacrolimus (Masuda et al., 2003). IL-18 is a pleiotropic cytokine that works both in Th1 and Th2 lymphocyte-mediated immunity. As a member of the IL-1 super family, IL-18 is a potent inducer of IFN-γ. IL-18 is involved in the pathogenesis of AD including Th1 and Th2 T lymphocyte-mediated immunity, including cytokine accumulation, and increase of IgE and histamine levels. Increased serum level of IL-18 and correlation with disease severity, eosinophil counts and serum sIL-2R levels was reported in several researches both in adult and children patients (Aral et al., 2006; Yoshizawa et al., 2002; Park &Youn, 2007; Sohn et al., 2004; Hon et al., 2004). IL-31 is a Th derived cytokine. Serum IL-31 was found over-expressed in both adults and paediatric AD and its serum level correlated

Little is known about the very early events of atopic skin inflammation. The unceasing amplification inflammation cycle in AD lesions might start with pruritus and the injury induced by scratching, and skin barrier disruption, resulting in proinflammatory cytokine

**clinical parameters References Expression in** 

Yoshizawa

Piancatelli

Aral et al., 2006

Yoshizawa

Nagy et al.,

Masuda et al.,

<sup>2003</sup>Increase

Belloni Fortina et al.,

2006

2009

**serum** 

et al., 2008 Increase Paediatric AD

No different

2011 Increase Mean :18.6 years;

Decrease under 10 years, no difference over 10 years

with controls. 5–12 year old

Increase Children

Adult:

median 22

Mean age 11.4 years with moderate AD

et al., 2002 Increase Adult

et al., 2002 Increase Adult

**Age of studied populations** 

(13–43years)

(1-184months)

(13–43years)

range: 7–49 years

aged 14 – 52 years,

positively with the disease severity (Raap et al., 2008; Ezzat et al., 2011).

**Correlation with other** 

Negative correlation with age and positive with SCORAD index

Positive correlation with

Positive correlation with

IL-2 Inverse correlation with serum IgE

SCORAD

SCORAD

IL-16 Positive correlation with serum total IgE

> No correlation with SCORAD index

Positive correlation with eosinophil count in peripheral blood and

IL-18 Not done Narbutt et al.,

IL-10

**Chemokines their receptors** 

**Interleukins** 

IL-12


Table 1. Literatures about serum interleukins in AD


Advances in Assessing the Severity of Atopic Dermatitis 179

Hon et al.,

Song et al.,

Jahnz-Rozyk

T.F.Leung et al., 2003

Kakinuma

2009

Nakazato

Mostafa et al.,

Jahnz-Rozyk

T.F.Leung et al., 2003

Kakinuma

<sup>2008</sup>Increase

<sup>2007</sup>Increase

<sup>2006</sup>Increase

**serum** 

et al., 2005 Increase Age (Mean±SD of

et al., 2001 Increase Mean age ± SEM:

et al., 2008 Increase Infants (mean age

et al., 2005 Increase Age: Mean±SD of

et al., 2002 Increase Not described

Higher in moderate AD than in mild

AD

Increase over 10 years old

No different between mild and moderate

AD

**Adult / childhood /infant phase** 

Aged younger than 18 years (mean ±SD: 10.7 ± 4.4 years)

24.7±10.7 years)

Median 2.1 years range 0.6-4.2 years

26.6 ± 8.9 years

Children (mean age 11.4 years with moderate AD

4.5 months)

24.7±10.7 years

Median 2.1 years range 0.6-4.2 years

Children (ages ranged between 2 and 10 years with a mean age of 5 ± 2.8 years)

Children (4.9±3.3 years, 2 months to 14 years)

**clinical parameters References Expressions in** 

**Chemokine** 

**Correlation with other** 

Positive correlation with

Positive correlation with serum CTACK and SCORAD

Positive correlation with

Positive correlation with SCORAD extent and intensity components, Positive correlation with CCL22, but not SCORAD

Correlation with eosinophil number, SCORAD index, serum sE-selectin and weakly correlated with serum sIL-2 receptor

Positive correlation with

Positive correlation with

Positive correlation with SCORAD index and its extent and intensity components, Positive correlation with CCL17

Positively related with SCORAD index, serum sEselectin, sIL-2R, TARC and eosinophil numbers in peripheral blood

Positive correlation with obj-SCORAD index, peripheral blood eosinophil counts and serum immunoglobulin E

SCORAD index

SCORAD index

/MDC Not done Narbutt et al.,

index; decreased in accordance with ages

SCORAD index

index

CCL22

SCORAD index


T.F.Leung et al., 2003

Jahnz-Rozyk

T.F.Leung et al., 2003

Miyahara et al., 2011

2009

Nakazato

Mostafa et al.,

<sup>2008</sup>Increase

**serum** 

<sup>2009</sup>Increase Children

Higher in moderate AD than in mild

Umbilical cord serum levels from neonates destined to develop AD in infancy were higher than in those from neonates who showed no signs of AD during infancy; Serum levels were higher in mothers with AD than in those without

AD

AD

AD.

Decrease under 10 years old, increase over 10 years old

et al., 2008 Increase Infants (mean age

No difference between mild and moderate

et al., 2005 Increase Age: Mean±SD of

**Adult / childhood /infant phase** 

Median 2.1 years, range 0.6-4.2 years

24.7±10.7 years

Median 2.1 years, range 0.6-4.2 years

Neonates and their mothers

Children (mean age 11.4 years with moderate AD)

4.5 months)

Children (ages ranged between 2 and 10 years with a mean age of 5 ± 2.8 years)

**clinical parameters References Expressions in** 

**Chemokine** 

CCL2 /MCP-1

CCL11 /eotaxin /EOX

CCL17 /TARC **Correlation with other** 

Did not correlate with SCORAD index and its extend and intensity

no significant relationship with TARC, MDC, IgE or

Positive correlate with SCORAD extent, but not

Positive correlation with soluble HLA-G. High umbilical cord serum levels were associated with infantile AD development

Not done Narbutt et al.,

Positive correlation with

Positive correlation with obj-SCORAD index, peripheral blood eosinophil counts and serum immunoglobulin E

SCORAD index

SCORAD index

SCORAD index.

CXCL12 Not done Narbutt et al.,


Advances in Assessing the Severity of Atopic Dermatitis 181

and chemokine production, directing the recruitment of pathogenic leukocytes to the skin (Steinhoff et al., 2006). There are many researches conformed that they are useful inflammatory markers for assessing severity of AD. Chemokines attract leukocytes transmigrate into the skin in AD by their gradients directing. Chemokine ligand-receptor interactions direct the multistep process of leukocyte migration. Chemokines can be classed into 4 subclasses according to the arrangement of N-terminal cysteine residues: CXC chemokines (CXCL); CC chemokines (CCL); C chemokines (XCL), and CX3C chemokine (CX3CL). To date, 45 human chemokine ligands and 10 CC chemokine, 7 CXC chemokine, 1 CX3C, and 1 XC receptors have been identified (Rossi & Zlotnik, 2000; Zlotnik &Yoshie, 2000; Balabanian et al., 2005). Many chemokines, including CCL1, CCL2, CCL3, CCL4, CCL5, CCL10, CCL11, CCL13, CCL17,CCL18, CCL20, CCL22, CCL26, CCL27, CCL28, CX3CL1,CXCL9, CXCL10,CXCL12,have been presumed to be involving in AD phenotype (Homey et al., 2006; Toda et al., 2003; Hayashida et al., 2011; Piancatelli et al., 2008; Jahnz-Rozyk et al., 2005; T.F.Leung et al., 2003; Miyahara et al., 2011; Hon et al., 2004,2007; Kagami et al., 2003,2005; Yoshizawa et al., 2002; Park&Youn, 2007; Kakinuma et al; 2003; Ezzat &Shaheen, 2009; Echigo et al., 2004) (in table2). These researches indicated that the imbalance in serum concentration of Th-1- and Th-2-derived chemokines may be one of the factors involved in pathogenesis of AD

CXCL9, CXCL10, and CXCL11 are Th-1-derived chemokines, while CCL11, CCL17, CCL22, CCL27 are Th-2-derived chemokines, leading to preferential influx of T1/Th2 lymphocytes to the lesion of AD respectively (Narbutt et al., 2009). CCL28 is recently identified to be selectively expressed by keratinocytes and its functional ligands are CCR3 and CCR10. CCL28 is similar to CCL27 in human, they shares 40% amino acid identity(Hieshima et al., 2003). CCL26, CCL11 through CCR3 contribute to eosinophils recruitment to the lesion of AD(Homey et al., 2006). CX3CL1 originates from the endothelial cell and its receptor is CX3CR1, which can direct several kinds of immunological effective cells (such as T cell, NK

Research by Narbutt J et al indicated that the serum level of CXCL9 and CXCL10 was decreased in childhood AD (Narbutt et al., 2009). While there were many study indicating that CCL11, CCL17, CCL22, CCL27 level in the serum were increased in AD patients and correlated with disease severity (T.F.Leung et al., 2003; Mostafa et al., 2008; Nagy et al., 2011; Song et al., 2006; Sohn et al., 2004; Kakinuma et al., 2002,2008; Jahnz-Rozyk et al., 2005; Hijnen et al., 2004; Kakinuma et al., 2001). Among the Th2 chemokines, serum CCL27 correlated most significantly with the severity of AD (Nakazato et al., 2008).The research by Miyahara et al showed that increased level of CCL17 in umbilical cord serum of neonates destined to develop AD in infancy (Miyahara et al., 2011).But another research indicated that the serum level of CCL17 and IL-18 were decreased, and CXCL12 and CCL27 increased in kids younger than 10 years old. In childhood AD of over 10 years old, serum concentration of CXCL12, CCL17, CCL22 was higher (Toda et al., 2003).There are many research results confirmed that the increased CCL28 level in the serum of AD patients and correlated positively to the severity scores (Jahnz-Rozyk et al., 2005; T.F. Leung et al., 2003; Ezzat &Shaheen ,2009; Kagami et al., 2005; Ezzat et al., 2009), so CCL28 may be a useful parameter in the clinical diagnosis and prognosis after proper treatment. CCL26, as a chemokine attract eosinophils to the skin lesion is elevated in the serum and significantly correlated with the serum CCL17 and CCL22 levels, peripheral blood eosinophil numbers

and biomarkers of AD disease severity.

cell and monocytes and DC) (Echigo et al., 2004).

and SCORAD index (Kagami et al., 2003).


Table 2. Literatures about serum chemokines in AD. Abbreviations used in the table: CXCL10/IP-10, IFN-induced protein of 10 kd; CCL2/MCP-1, monocyte chemotactic protein 1; CCL11 /eotaxin (EOX); CCL17/TARC, thymus and activation-regulated chemokine; CCL22/MDC, macrophage-derived chemokine; CCL26/eotaxin-3; CCL27/CTACK, cutaneous T cell–attracting chemokine; CCL28/MEC, Mucosa-associated epithelial chemokine; CX3CL1/fractalkine; sE-selectin, serum soluble E-selectin; sIL-2R, soluble interleukin-2 receptor.

Kagami et al.,

**serum** 

2003 Increase Adult (mean±SD:

Increase under 10 years old

et al., 2008 Increase Infants (mean age

**Adult / childhood /infant phase** 

28·7±7·1 years)

Children (mean age 11.4 years with moderate AD

4.5 months)

Children: 4.9±3.3 years, 2 months to 14 years

Children: median age of 5 (range: 1–11 years)

Adult(mean ± SEM age, 28.5 ± 6.8 years)

Ages ranged between 8 and 120

(mean ± SD: 47 ± 22 months)

28.7± 6.7 years)

months

years

2005 Increase Adults(mean±SD:

2004 Increase Age: 24.7 ± 7.4

Aged younger than 18 years (mean ±SD: 10.7 ± 4.4)

**clinical parameters References Expressions in** 

2009

Nakazato

Hon et al.,

Song et al.,

Hon et al.,

Kakinuma

Ezzat et al.,

Echigo et al.,

Table 2. Literatures about serum chemokines in AD. Abbreviations used in the table: CXCL10/IP-10, IFN-induced protein of 10 kd; CCL2/MCP-1, monocyte chemotactic protein 1; CCL11 /eotaxin (EOX); CCL17/TARC, thymus and activation-regulated chemokine; CCL22/MDC, macrophage-derived chemokine; CCL26/eotaxin-3; CCL27/CTACK, cutaneous T cell–attracting chemokine; CCL28/MEC, Mucosa-associated epithelial chemokine; CX3CL1/fractalkine; sE-selectin, serum soluble E-selectin; sIL-2R, soluble

<sup>2007</sup>Increase

<sup>2006</sup>Increase

<sup>2004</sup>Increase

et al., 2003 Increase

<sup>2009</sup>Increase

**Chemokine** 

CCL26 /eotaxin-3

CCL27

CCL28/ MEC

CX3CL1 /fractalkine

interleukin-2 receptor.

**Correlation with other** 

Positive correlation with the serum CCL17 ,CCL22 levels, eosinophil numbers in peripheral blood and SCORAD index

/CTACK Not done Narbutt et al.,

Positive correlation with

Positive correlation with

Positive correlation with their serum TARC; SCORAD

Positive correlated with

Positive correlation with SCORAD index, sIL-2 receptor, sE-selectin,TARC,

Positive correlation with LSS

peripheral eosinophil counts,

Positively associated with the scoring system proposed by Rajka and Langeland.

Not done Kagami et al.,

index; decreased in accordance with their ages

SCORAD index

MDC in serum

and SCORAD index,

and serum LDH

SCORAD index

SCORAD index

and chemokine production, directing the recruitment of pathogenic leukocytes to the skin (Steinhoff et al., 2006). There are many researches conformed that they are useful inflammatory markers for assessing severity of AD. Chemokines attract leukocytes transmigrate into the skin in AD by their gradients directing. Chemokine ligand-receptor interactions direct the multistep process of leukocyte migration. Chemokines can be classed into 4 subclasses according to the arrangement of N-terminal cysteine residues: CXC chemokines (CXCL); CC chemokines (CCL); C chemokines (XCL), and CX3C chemokine (CX3CL). To date, 45 human chemokine ligands and 10 CC chemokine, 7 CXC chemokine, 1 CX3C, and 1 XC receptors have been identified (Rossi & Zlotnik, 2000; Zlotnik &Yoshie, 2000; Balabanian et al., 2005). Many chemokines, including CCL1, CCL2, CCL3, CCL4, CCL5, CCL10, CCL11, CCL13, CCL17,CCL18, CCL20, CCL22, CCL26, CCL27, CCL28, CX3CL1,CXCL9, CXCL10,CXCL12,have been presumed to be involving in AD phenotype (Homey et al., 2006; Toda et al., 2003; Hayashida et al., 2011; Piancatelli et al., 2008; Jahnz-Rozyk et al., 2005; T.F.Leung et al., 2003; Miyahara et al., 2011; Hon et al., 2004,2007; Kagami et al., 2003,2005; Yoshizawa et al., 2002; Park&Youn, 2007; Kakinuma et al; 2003; Ezzat &Shaheen, 2009; Echigo et al., 2004) (in table2). These researches indicated that the imbalance in serum concentration of Th-1- and Th-2-derived chemokines may be one of the factors involved in pathogenesis of AD and biomarkers of AD disease severity.

CXCL9, CXCL10, and CXCL11 are Th-1-derived chemokines, while CCL11, CCL17, CCL22, CCL27 are Th-2-derived chemokines, leading to preferential influx of T1/Th2 lymphocytes to the lesion of AD respectively (Narbutt et al., 2009). CCL28 is recently identified to be selectively expressed by keratinocytes and its functional ligands are CCR3 and CCR10. CCL28 is similar to CCL27 in human, they shares 40% amino acid identity(Hieshima et al., 2003). CCL26, CCL11 through CCR3 contribute to eosinophils recruitment to the lesion of AD(Homey et al., 2006). CX3CL1 originates from the endothelial cell and its receptor is CX3CR1, which can direct several kinds of immunological effective cells (such as T cell, NK cell and monocytes and DC) (Echigo et al., 2004).

Research by Narbutt J et al indicated that the serum level of CXCL9 and CXCL10 was decreased in childhood AD (Narbutt et al., 2009). While there were many study indicating that CCL11, CCL17, CCL22, CCL27 level in the serum were increased in AD patients and correlated with disease severity (T.F.Leung et al., 2003; Mostafa et al., 2008; Nagy et al., 2011; Song et al., 2006; Sohn et al., 2004; Kakinuma et al., 2002,2008; Jahnz-Rozyk et al., 2005; Hijnen et al., 2004; Kakinuma et al., 2001). Among the Th2 chemokines, serum CCL27 correlated most significantly with the severity of AD (Nakazato et al., 2008).The research by Miyahara et al showed that increased level of CCL17 in umbilical cord serum of neonates destined to develop AD in infancy (Miyahara et al., 2011).But another research indicated that the serum level of CCL17 and IL-18 were decreased, and CXCL12 and CCL27 increased in kids younger than 10 years old. In childhood AD of over 10 years old, serum concentration of CXCL12, CCL17, CCL22 was higher (Toda et al., 2003).There are many research results confirmed that the increased CCL28 level in the serum of AD patients and correlated positively to the severity scores (Jahnz-Rozyk et al., 2005; T.F. Leung et al., 2003; Ezzat &Shaheen ,2009; Kagami et al., 2005; Ezzat et al., 2009), so CCL28 may be a useful parameter in the clinical diagnosis and prognosis after proper treatment. CCL26, as a chemokine attract eosinophils to the skin lesion is elevated in the serum and significantly correlated with the serum CCL17 and CCL22 levels, peripheral blood eosinophil numbers and SCORAD index (Kagami et al., 2003).

Advances in Assessing the Severity of Atopic Dermatitis 183

increased. After recovery of the patients, the serum LDH activity tended to decline. But there are no correlation between the LDH level and eosinocyte count in the peripheral blood

Matrix metalloproteinases(MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), are involved in inflammation mediated tissue destruction and remodeling. The maintenance of homeostasis of MMPs/TIMPs in the lesion is regulated by proinflammatory cytokines and growth factors (Woessner, 2001). In the study of Katoh N et al, they found that the level of TIMP-1 in the serum of AD patients was significantly increased, but reduced after treatments. The TIMP-1 level correlated with peripheral eosinophil counts, serum levels of IgE and LDH, eruption score, and eruption area. Moreover, the patients with chronic eruptions (lichenification and prurigo) had significantly higher TIMP-1 levels, while those with acute lesions were not correlated with TIMP-1 level in the serum. The authors gave a hypothesis that serum TIMP-1 level may be a useful

Human tissue kallikreins, or kallikrein-related peptidases (KLKs), are the largest family of trypsin- or chymotrypsin-like serine proteases (SPs). At least eight KLKs are expressed in normal skin, of which KLK8, KLK5, KLK7 have been reported to be the most important KLKs involved in maintenance of the homeostasis of normal epidermis by cleaving corneodesmosomes. Moreover, KLK5 and KLK14 activate protease-activated receptor (PAR)-2, which is a signaling receptor in epidermal inflammation and a regulator of epidermal barrier function (Meyer-Hoffert, 2009). In the lesion of AD, the level of KLKs were increased (Voegeli et al., 2009). In the serum of AD, KLK8 was reported significantly elevated, while KLK5 and KLK11 were significantly decreased (Komatsu et al., 2007). The different expression between lesion and serum may be due to the diversity of the origins of

Neopterin is biosynthesized from guanosine triphosphate and produced preferentially by monocytes and macrophages. Increased neopterin concentrations in serum or urine are connected with diseases linked with cellular immune reaction. Recently, serum neopterin levels was reported to increase and to be considered as a diagnostic marker of AD

The serum levels of SIRs ,such as sCD14, sCD23, sCD25 and sCD30 have been reported to be associated with AD (Ott et al., 2010; El Mongy et al., 2008; Di Lorenzo er al., 2003; Hon et al., 2005; Furue et al., 1999). CD30 released by CD30+ cells, a member of the TNF receptor superfamily, is a costimulatory molecule expressed on activated T and B cells. After cell activation, its extracellular domain generates soluble CD30 (sCD30) by enzymatic cleavage. Serum sCD30 is regarded as a indicator of Th2-type immune responses (El Mongy et al., 2008). Although there were several researches indicated that serum sCD30 levels were significantly higher and correlated positively with the severity of AD as assessed by SCORAD, age and duration of the disease (El Mongy et al., 2008; Di Lorenzo et al., 2003). Ott H et al indicated that the serum level of sCD23, sCD25 and sCD30 were highly aged dependent and can not

be regarded as useful biomarkers for assessment of childhood AD (Ott et al., 2010).

Serum immunoglobulin free light chains (FLC) is classically associated with monoclonal gammopathies. An significantly increased level of FLC was observed in severe AD , while

marker to estimate the long-term disease activity of AD (Katoh et al., 2002).

or serum IgE level (Morishima et al., 2010).

KLKs from many tissues and organs.

**2.3.2.6 Soluble immune receptors (SIRs)** 

(Ciprandi et al., 2011).

**2.3.2.7 Others in serum** 

Taken together, interleukins and chemokines are important markers in AD. But the normal levels in infancy and age-specific analysis in atopic dermatitis of these markers have not been well determined, this should be taken into account when interpreting the results, especially in infant AD.

### **Tumor necrosis factor(TNF)**

B cell-activating factor (BAFF) is a member of tumour necrosis factor superfamily. BAFF plays an important role in the survival and maturation of B lymphocyte cells. The level of serum BAFF in childhood AD patients increased and significantly correlated with total serum IgE level and total eosinophil count in peripheral blood(Jee et al., 2010).While , in another research, serum BAFF level was not elevated in patients with AD (Matsushita et al., 2008).

#### **Neurotrophins and neuropeptides,Growth factors and hormones**

The Neurotrophins (NT) family including Nerve growth factor (NGF), Brain-derived neurotrophic factor (BDNF), NT- 3,4,5, 6 and NT- 7 (Leibrock et al., 1989; Kolbeck et al., 1994). The biologic effects of NT family are not merely restricted to the central nervous system but also relevant to the nerve cells present in other organs including the skin. More and more studies have demonstrated that NTs play an important role in the pathogenesis of AD. Association of BDNF gene polymorphisms and the increased serum levels in AD patients was conformed. The level of BDNF in the serum was correlated with intrinsic type of AD severity (Ma et al.,2010; Raap et al., 2006).While the level of NGF in serum has no significant correlation with total IgE, or severity of disease assessed by SCORAD (Schulte-Herbruggen et al., 2007). Although serum levels of vasoactive intestinal peptide (VIP) are found to be increased in patients with AD, there was no correlation between serum VIP levels and disease severity, serum LDH levels, total serum IgE levels, and peripheral blood eosinophil counts in patients with AD (Umemoto er al., 2003). Also there was also no association between serum VIP concentration and itch intensity (C.H.Lee et al., 2006). A study showed TEWL, serum IgE and beta-endorphin were independent parameters for assessing itch intensity in AD (C.H.Lee et al., 2006).

Mast cell in the lesions is thought to play an important role in the pathogenesis of AD. Stem cell factor (SCF), and the interaction of SCF and its receptor, KIT (tyrosine kinase transmembrane receptor) are the key factors that induce mast cell growth, migration and differentiation. Serum levels of soluble SCF and soluble KIT were significantly elevated in AD patients, positively correlated with the disease severity, and decreased after effective treatment with topical corticosteroids (Kanbe et al., 2001).

Significantly higher expression of thymic stromal lymphopoietin (TSLP), an IL-7 – like cytokine, by lesional skin can induce DCs to express Th2 cell – polarizing signals in AD. DCs activated by TSLP can induce Th0 to differentiate into Th2 cells and play important roles in the maintenance and regulation of Th2 memory cells (Wang et al., 2006). While the serum TSLP level is inconsistent by different clinical study (E.B.Lee et al., 2010; Alysandratos et al., 2010; Nakamura et al., 2008).

The increasing level of serum antidiuretic hormone (ADH) in severe AD was confirmed , which was related with TEWL(Aoki, et al., 2005).

#### **2.3.2.5 Enzymes**

In the AD lesion, high lactate dehydrogenase(LDH) activity was found , especially in the epidermis. Also in the serum, the level of LDH and its isozyme (LDH4 and LDH5) is

Taken together, interleukins and chemokines are important markers in AD. But the normal levels in infancy and age-specific analysis in atopic dermatitis of these markers have not been well determined, this should be taken into account when interpreting the results,

B cell-activating factor (BAFF) is a member of tumour necrosis factor superfamily. BAFF plays an important role in the survival and maturation of B lymphocyte cells. The level of serum BAFF in childhood AD patients increased and significantly correlated with total serum IgE level and total eosinophil count in peripheral blood(Jee et al., 2010).While , in another research,

The Neurotrophins (NT) family including Nerve growth factor (NGF), Brain-derived neurotrophic factor (BDNF), NT- 3,4,5, 6 and NT- 7 (Leibrock et al., 1989; Kolbeck et al., 1994). The biologic effects of NT family are not merely restricted to the central nervous system but also relevant to the nerve cells present in other organs including the skin. More and more studies have demonstrated that NTs play an important role in the pathogenesis of AD. Association of BDNF gene polymorphisms and the increased serum levels in AD patients was conformed. The level of BDNF in the serum was correlated with intrinsic type of AD severity (Ma et al.,2010; Raap et al., 2006).While the level of NGF in serum has no significant correlation with total IgE, or severity of disease assessed by SCORAD (Schulte-Herbruggen et al., 2007). Although serum levels of vasoactive intestinal peptide (VIP) are found to be increased in patients with AD, there was no correlation between serum VIP levels and disease severity, serum LDH levels, total serum IgE levels, and peripheral blood eosinophil counts in patients with AD (Umemoto er al., 2003). Also there was also no association between serum VIP concentration and itch intensity (C.H.Lee et al., 2006). A study showed TEWL, serum IgE and beta-endorphin were independent parameters for assessing itch

Mast cell in the lesions is thought to play an important role in the pathogenesis of AD. Stem cell factor (SCF), and the interaction of SCF and its receptor, KIT (tyrosine kinase transmembrane receptor) are the key factors that induce mast cell growth, migration and differentiation. Serum levels of soluble SCF and soluble KIT were significantly elevated in AD patients, positively correlated with the disease severity, and decreased after effective

Significantly higher expression of thymic stromal lymphopoietin (TSLP), an IL-7 – like cytokine, by lesional skin can induce DCs to express Th2 cell – polarizing signals in AD. DCs activated by TSLP can induce Th0 to differentiate into Th2 cells and play important roles in the maintenance and regulation of Th2 memory cells (Wang et al., 2006). While the serum TSLP level is inconsistent by different clinical study (E.B.Lee et al., 2010; Alysandratos et al.,

The increasing level of serum antidiuretic hormone (ADH) in severe AD was confirmed ,

In the AD lesion, high lactate dehydrogenase(LDH) activity was found , especially in the epidermis. Also in the serum, the level of LDH and its isozyme (LDH4 and LDH5) is

serum BAFF level was not elevated in patients with AD (Matsushita et al., 2008).

**Neurotrophins and neuropeptides,Growth factors and hormones** 

especially in infant AD. **Tumor necrosis factor(TNF)** 

intensity in AD (C.H.Lee et al., 2006).

2010; Nakamura et al., 2008).

**2.3.2.5 Enzymes** 

treatment with topical corticosteroids (Kanbe et al., 2001).

which was related with TEWL(Aoki, et al., 2005).

increased. After recovery of the patients, the serum LDH activity tended to decline. But there are no correlation between the LDH level and eosinocyte count in the peripheral blood or serum IgE level (Morishima et al., 2010).

Matrix metalloproteinases(MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), are involved in inflammation mediated tissue destruction and remodeling. The maintenance of homeostasis of MMPs/TIMPs in the lesion is regulated by proinflammatory cytokines and growth factors (Woessner, 2001). In the study of Katoh N et al, they found that the level of TIMP-1 in the serum of AD patients was significantly increased, but reduced after treatments. The TIMP-1 level correlated with peripheral eosinophil counts, serum levels of IgE and LDH, eruption score, and eruption area. Moreover, the patients with chronic eruptions (lichenification and prurigo) had significantly higher TIMP-1 levels, while those with acute lesions were not correlated with TIMP-1 level in the serum. The authors gave a hypothesis that serum TIMP-1 level may be a useful marker to estimate the long-term disease activity of AD (Katoh et al., 2002).

Human tissue kallikreins, or kallikrein-related peptidases (KLKs), are the largest family of trypsin- or chymotrypsin-like serine proteases (SPs). At least eight KLKs are expressed in normal skin, of which KLK8, KLK5, KLK7 have been reported to be the most important KLKs involved in maintenance of the homeostasis of normal epidermis by cleaving corneodesmosomes. Moreover, KLK5 and KLK14 activate protease-activated receptor (PAR)-2, which is a signaling receptor in epidermal inflammation and a regulator of epidermal barrier function (Meyer-Hoffert, 2009). In the lesion of AD, the level of KLKs were increased (Voegeli et al., 2009). In the serum of AD, KLK8 was reported significantly elevated, while KLK5 and KLK11 were significantly decreased (Komatsu et al., 2007). The different expression between lesion and serum may be due to the diversity of the origins of KLKs from many tissues and organs.

Neopterin is biosynthesized from guanosine triphosphate and produced preferentially by monocytes and macrophages. Increased neopterin concentrations in serum or urine are connected with diseases linked with cellular immune reaction. Recently, serum neopterin levels was reported to increase and to be considered as a diagnostic marker of AD (Ciprandi et al., 2011).

### **2.3.2.6 Soluble immune receptors (SIRs)**

The serum levels of SIRs ,such as sCD14, sCD23, sCD25 and sCD30 have been reported to be associated with AD (Ott et al., 2010; El Mongy et al., 2008; Di Lorenzo er al., 2003; Hon et al., 2005; Furue et al., 1999). CD30 released by CD30+ cells, a member of the TNF receptor superfamily, is a costimulatory molecule expressed on activated T and B cells. After cell activation, its extracellular domain generates soluble CD30 (sCD30) by enzymatic cleavage. Serum sCD30 is regarded as a indicator of Th2-type immune responses (El Mongy et al., 2008). Although there were several researches indicated that serum sCD30 levels were significantly higher and correlated positively with the severity of AD as assessed by SCORAD, age and duration of the disease (El Mongy et al., 2008; Di Lorenzo et al., 2003). Ott H et al indicated that the serum level of sCD23, sCD25 and sCD30 were highly aged dependent and can not be regarded as useful biomarkers for assessment of childhood AD (Ott et al., 2010).

#### **2.3.2.7 Others in serum**

Serum immunoglobulin free light chains (FLC) is classically associated with monoclonal gammopathies. An significantly increased level of FLC was observed in severe AD , while

Advances in Assessing the Severity of Atopic Dermatitis 185

factors, such as gene, environment, race, age etc. Further studies should be performed to findings of definitive biomarkers to assess the disease severity and evaluation of treatment effects. But the normal levels in infancy and age-specific analysis in AD of these markers have not been well determined, this should be taken into account when interpreting the

results, especially in infant AD.

Hanifin and Rajka diagnostic criteria (H-R criteria);

Dermatitis Area and Severity Index score (ADASIS);

Children's Dermatology Life Quality Index (CDLQI);

Scoring Atopic Dermatitis index (SCORAD);

Eczema Area and Severity Index (EASI); Psoriasis area and severity index (PASI); Nottingham Eczema Severity Score (NESS);

Stratum corneum hydration (SCH); Trans-epidermal water loss (TEWL);

Natural moisturizing factors (NMF); Pyrrolidone carboxylic acid (PCA);

Eosinophil cationic protein (ECP);

CCL2/MCP-1, monocyte chemotactic protein 1;

CCL22 /MDC, macrophage-derived chemokine;

CXCL10 /IP-10, IFN-induced protein of 10 kd;

sE-selectin, serum soluble E-selectin ; sIL-2R, soluble interleukin-2 receptor .

Tumor necrosis factor (TNF); B cell-activating factor (BAFF);

Body surface area (BSA); Stratum corneum (SC);

Urocanic acid (UCA); Atopy patch test (APT); Skin prick test (SPT);

T-regulatory (Treg); Interleukin (IL);

CCL26 /eotaxin-3;

CX3CL1 /fractalkine;

Neurotrophins (NT); Nerve growth factor (NGF);

CCL11 /eotaxin (EOX);

International Study of Asthma and Allergies in Childhood (ISAAC);

Objective severity assessment of atopic dermatitis (OSAAD system);

Eosinophil derived neurotoxin/eosinophil protein X (EDN/EPX);

CCL17 /TARC, thymus and activation-regulated chemokine;

CCL27/CTACK, cutaneous T cell–attracting chemokine; CCL28/ MEC, Mucosa-associated epithelial chemokine;

**4. Abbreviations** 

Atopic dermatitis (AD);

Quality of life (QoL);

the association of FLC levels with age or total IgE levels was not confirmed (Kayserova et al., 2010).Vitamin D deficiency may be related to the severity of AD in the children patients. The level of serum in severe AD was significant lower than the mild AD (Peroni et al., 2010).

### **2.3.3 Biomarkers in urine**

Leukotriene B4 (LTB4), LTC4, LTD4 and LTE4, the products of the oxidative metabolism of cell membrane arachidonic acid are secreted from eosinophils, mast cells and other inflammatory cells. As LTE4 is stable in urine, the urinal level of LTE4 may be a good marker for activation of mast cells and eosinophils in vivo. Urinary LTE4 increased in severe AD and correlated with severity of AD in children had been confirmed. Those having to sensitization to common allergens had higher LTE4 level than those without in the severe AD (Hon et al., 2004; Oymar &Aksnes, 2005).

EDN/EPX, one of the major proinflammatory mediators released by activated eosinophils, can induce severe tissue damage and maintenance and exacerbation of AD. A positive correlation between the SCORAD and serum ECP and urine EPX levels has been reported in children and adult patients (Breuer et al., 2001; Pucci et al., 2005; Pucci et al., 2000; Goto et al., 2007),also correlated with visual analog scales (VAS) scores for itching(Goto et al., 2007). While urinary EDN concentrations did not correlate with the number of eosinophils in the peripheral blood (Goto et al., 2007).

Urinary nitrate level significantly increased in AD patients. The severity and extent of AD significantly correlated with urinary nitrate and malondialdehyde level, but it did not correlate with urinary 8-hydroxydeoxyguanosine (8-OHdG) level (Nakai et al., 2009).

The increased TEWL in AD is attributable partly to impaired barrier function of the skin. Remarkable loss of body fluid would induce a series of systemic regulatory reactions. The functional antidiuretic hormone (ADH)–aquaporin (AQP)-2 axis is a major regulatory system to keep water balance. Increased serum ADH was detected in severe AD, a result possibly due to a dehydrated state caused by increased TEWL in these patients (Aoki, 2005). Recently, Urinary aquaporin-2 was found to be increased in infant AD patients, and positively correlate with skin dryness of infant AD, but its concentrations did not correlate with the number of eosinophils in the peripheral blood and the total IgE level in serum and disease severity (Di et al., 2010).

Increased neopterin levels in serum or urine are connected with diseases related with cellular immune reaction (Murr et al., 2002).In the association study by Horak E et al between neopterin in cord blood and urine in early childhood and the development of atopic dermatitisAD, they showed that family history of atopic disease was associated with lower urinary neopterin levels at age of 6 years (Horak er al., 2006).

Prostaglandin D2 (PGD2), the major cyclooxygenase product of mast cells, is a good marker for mast cell activation. In the lung, PGD2 converts to 9a, 11b-prostaglandin F2 (9a,11b-PGF2), which can be detected in the urine (O'Sullivan, 1999). The study of Oymar K and Aksnes L indicated that 9a, 11b-PGF2 level in the urine of severe childhood AD patients was increased and indicated that 9a, 11b-PGF2 may be a useful biomarker of mast cell activation in the urine (Oymar &Aksnes, 2004).
