EFFECT OF PREGNANT MOUSE SERUM ON INDUCTION OF INDOLAMINE 2, 3- DIOXYGENASE IN DENDRITIC CELLS

Introduction: Several studies have shown that many factors are involved in the maternal tolerance to the fetus. Indolamine 2, 3dioxygenase (IDO) enzyme which catabolizes tryptophan is one of the factors that have been reported to play an important role leading to a successful pregnancy. The objective of this study was to evaluate the effects of pregnant mouse serum on the induction of indolamine 2, 3 dioxygenase in dendritic cells (DCs) which may be used as a basis for practical studies on the immunological bases of recurrent abortions. Materials & Methods: Allogenic pregnant mice sera were collected in mid-pregnancy. DCs were isolated from Balb/c mouse spleen through a three-step method, including: Collagenase digestion of spleen tissue, low density cells separation via the Nycodenz density gradient centrifugation and plastic adherence. T cells were isolated from C57BL/6 mouse lymph nodes through nylon wool method. As stimulator cells, pregnant and non-pregnant mice sera treated DCs were irradiated and co-cultured with purified T cells (allogenic MLR). 1-methyl-tryptophan (1-MT), as the specific inhibitor of IDO, was added to some wells of MLR assay in different concentrations and T cells proliferation response was measured by H-Thymidine incorporation. The MLR supernatant was also analyzed by HPLC for its tryptophan and kynurenin (Trp metabolite) content. All tests were repeated for 5 times. Man-Whitney′s nonparametric test was used to evaluate the differences among groups. Confidence interval was 95% and p-values <0.05 were regarded as significant. Results: The results showed the ability of pregnant mice sera to reduce the dendritic cells ability in T cell proliferation induction compared to non-pregnant mice sera but addition of 1-MT did not have any significant effect on this inhibition. Additionally, IDO metabolites concentration assessment in the presence or absence of 1-MT, through HPLC method, did not show any significant difference. Conclusion: There are many factors in pregnant mice sera such as progesterone, IL-10, Vit D3, etc. Which might cause inhibition of T lymphocyte proliferation response in allogenic MLR through affecting DCs' efficiency. Although it seems that IDO expression by DCs is not responsible for decrease in T cell proliferation after treatment of DCs by pregnant mice sera, thus some other mechanisms might be responsible for this phenomenon which their identification needs more investigation.