**8. Association of OPRM1 functional alleles with immune cell function**

Sharad et al*.* [93] used a genetic approach to correlate a functional *OPRM1* gene polymorphism with known action of opiates on immunity and undertook a prospective study to understand the relationship of the 118G variation with the amount of exogenous opiates consumed and correlated the immunosuppressive effects of exogenous opiates with the *OPRM1* allele type. They studied the immune status of opiate users by measuring serum Ig (IgG and IgA) levels, in association with specific *OPRM1* genotype, and confirmed that the mean circulating levels of Ig were significantly lower in opiate users when compared with levels in cohort controls. Among opiate-dependent subjects, individuals with AA genotype were found to have the lowest levels of circulating immunoglobulins, both IgG and IgA (p = 0.0001), while the AG genotype carrying individuals had a higher level of both immunoglobulins. The homozygous GG genotype was in between the AA and AG genotypes. Alternatively, in opiate naïve subjects, the AA individuals showed the highest titers of

**93**

molecular exploration.

*Immune Cell Activation: Stimulation, Costimulation, and Regulation of Cellular Activation*

circulating IgG, and the GG individuals showed the lowest with AG having intermediate values [94]. The immunosuppressive effects documented in opiate naïve individuals can be attributed to altered regulation of PKA and pERK1/2 due to the levels of endogenous opioid. In addition to the absence of G genotype in the immortalized cell lines and based on the cell culture data showing cell cycle arrest observed in the present study (in A549 and HepG2 cell lines), we hypothesize that coactivation

of μOR in presence of 118G allele leads to a suppression/arrest of cell division. To test this hypothesis, another pilot study was carried out in which healthy opiate naïve volunteers were enrolled and the cell count for circulating lymphocyte subsets was studied as a measure of immune competence. Genotypic association studies showed a correlation between the immune cell numbers. Total lymphocyte count showed a significant lowering in cell numbers in 118G-allele-bearing individuals when compared to 118A-bearing individuals. However, cell numbers in all individuals remained within the documented normal range of 500–4000 cell/ml. The GG allele individuals showed significantly lower cell count, averaging 490, which differed markedly from cell numbers observed in AA-bearing individuals with mean numbers of 1976 cells/ml, (p = 0.008) and a correlation factor, r2

0.79 between the genotype and average cell numbers. Our data show a significant lowering in all immunocytes, namely leucocyte populations (CD45+ve cells), B lymphocytes (CD10+ve cells), T lymphocytes (CD3, CD4, and CD8+ve cells), NK cells (CD56+ve cells), activated monocytes (CD 11b+ve cells), and mesenchymal progenitors in GG-bearing individuals when compared to AA-allele-bearing individuals but not always in comparison with those bearing the AG allele. This baseline lowering of cell numbers in GG-bearing individuals supports the hypothesis that GG genotype suppresses cell division, and since mounting of a successful immune response and/or overstimulation of immune system, as in case of patients with autoimmune disorders, depends on activation of both innate and adaptive immune responses, the 118G-bearing individuals would be prone to immune suppression due to lack of amplification by selective cell division, a critical step in elimination of

In conclusion, there is a significant correlation between the circulating number of lymphocytes TH and Tc, B cells and NK cells, and the μOR allele present, and this difference can be further increased in the presence of exogenous opioids either during clinical treatment or substance dependence, as the 118G allele affects the process of cell division arresting cells at the S or M phase of the cell cycle, or by modulating the action of cell division–linked secretion of stimulating cytokines/chemokine known to induce clone-specific and cell type–specific proliferation, because of the propensity of opioid receptor to heterodimerize and to selectively bias the subsequent ligand engagement/s with the dimerized/ oligomerized receptors. This "subliminal immune suppression" in G allele–bearing individuals can have far reaching impact on onset of diseases such as cancer and obesity (both have an element inflammation) and vaccination for infectious diseases and even dreaded diseases as cancer. This immune suppression will certainly lower the individual's risk for autoimmune disorders such as rheumatoid arthritis, lupus, etc. The relationship between the μOR-mediated cell signaling and impact of stimulation of MOR as partner receptors, which influences binding of the second ligand in immunocytes and thereby the outcome on immune cells function in mounting and regulating the immune response/s, needs more detailed

the pathogen or an autoimmune response to an antigen.

**9. Conclusion and future perspectives**

of

*DOI: http://dx.doi.org/10.5772/intechopen.81568*

#### *Immune Cell Activation: Stimulation, Costimulation, and Regulation of Cellular Activation DOI: http://dx.doi.org/10.5772/intechopen.81568*

circulating IgG, and the GG individuals showed the lowest with AG having intermediate values [94]. The immunosuppressive effects documented in opiate naïve individuals can be attributed to altered regulation of PKA and pERK1/2 due to the levels of endogenous opioid. In addition to the absence of G genotype in the immortalized cell lines and based on the cell culture data showing cell cycle arrest observed in the present study (in A549 and HepG2 cell lines), we hypothesize that coactivation of μOR in presence of 118G allele leads to a suppression/arrest of cell division.

To test this hypothesis, another pilot study was carried out in which healthy opiate naïve volunteers were enrolled and the cell count for circulating lymphocyte subsets was studied as a measure of immune competence. Genotypic association studies showed a correlation between the immune cell numbers. Total lymphocyte count showed a significant lowering in cell numbers in 118G-allele-bearing individuals when compared to 118A-bearing individuals. However, cell numbers in all individuals remained within the documented normal range of 500–4000 cell/ml. The GG allele individuals showed significantly lower cell count, averaging 490, which differed markedly from cell numbers observed in AA-bearing individuals with mean numbers of 1976 cells/ml, (p = 0.008) and a correlation factor, r2 of 0.79 between the genotype and average cell numbers. Our data show a significant lowering in all immunocytes, namely leucocyte populations (CD45+ve cells), B lymphocytes (CD10+ve cells), T lymphocytes (CD3, CD4, and CD8+ve cells), NK cells (CD56+ve cells), activated monocytes (CD 11b+ve cells), and mesenchymal progenitors in GG-bearing individuals when compared to AA-allele-bearing individuals but not always in comparison with those bearing the AG allele. This baseline lowering of cell numbers in GG-bearing individuals supports the hypothesis that GG genotype suppresses cell division, and since mounting of a successful immune response and/or overstimulation of immune system, as in case of patients with autoimmune disorders, depends on activation of both innate and adaptive immune responses, the 118G-bearing individuals would be prone to immune suppression due to lack of amplification by selective cell division, a critical step in elimination of the pathogen or an autoimmune response to an antigen.
