Expression of indoleamine 2,3-dioxygenase in pregnant mice correlates with CD4+CD25+Foxp3+ T regulatory cells

OBJECTIVE: Indoleamine 2,3-dioxygenase (IDO) initiated tryptophan degradation in the placenta has a role in the prevention of allogeneic fetus rejection by T-cells. The present study aimed to investigate the relationship between IDO and CD4(+)CD25(+)Foxp3(+) T cells in pregnant mice. MATERIALS AND METHODS: The percentage of CD4(+)CD25(+)Foxp3(+) T cells in peripheral blood mononuclear cells (PBMC) and IDO mRNA levels were detected in pregnant mice. The non-pregnant mice were used as control in this study. To confirm the effect of IDO, 1-methyl-trytophan (IDO inhibitor) was used in this study. RESULTS: The percentage of CD4(+)CD25(+)Foxp3(+) T cells in PBMC in pregnant mice was significantly higher than this in non-pregnant mice controls from day-6 to the end of the study (p<0.05). IDO mRNA levels in PBMC also markedly increased after pregnancy. The upregulation of IDO expression reached a maximum at day 18 after pregnancy (p<0.05). Compared to the pregnant group, the inhibitor could significantly decrease the IDO expression and Treg percentage (p<0.05). There was a positive association between IDO mRNA and CD4(+)CD25(+)Foxp3(+) T cells percentage. CONCLUSIONS: The results suggested IDO might play a role in the generation of CD4(+)CD25(+)Foxp3(+) T cells in pregnant mice.