The evaluation of PD-1 and Tim-3 expression besides their related miRNAs in PBMCs of women with recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a multifactorial disorder, associated with immunologic abnormalities. During pregnancy, the maternal immune system uses different tolerance mechanisms to deal with a semi-allogenic fetus. The expression of immune checkpoints and their related miRNAs in immune cells can ensure pregnancy at the feto-maternal interface by modulating immune responses. This study aims to evaluate the expression of the immune checkpoint molecules PD -1 and Tim -3 on circulating T cells by flow cytometry, that of mir-138 and mir155 in PBMCs by Real-time PCR, and the concentrations of TGF-beta and IP-10 in the sera of women suffering from RPL as well as of gestational age -matched healthy pregnant women by ELISA. The percentage of PD -1 or Tim -3 expressing CD8+ T cells was significantly lower in RPL patients compared to the controls, while there was no significant difference in Tim -3 expression of CD4+ T cells between the two groups. The mRNA of both the PD -1 and Tim -3 genes were downregulated in PBMCs of RPL patients compared to controls, however, the difference was not statistically significant for Tim -3. The concentration of TGF-beta was significantly lower and that of IP-10 was significantly higher in the sera of RPL patients than in those of the controls. The relative expression of mir138 and miR-155 were significantly lower, in PBMCs of RPL patients than in those of healthy pregnant women. These data confirm that by affecting cytokine production, immune checkpoints, and microRNAs play a role in establishing the appropriate local immune environment for successful pregnancy. The wider analysis of immune checkpoints may also yield new biomarkers for the diagnosis and prevention of RPL.