Distinct changes of in BTLA, ICOS, PD-1, and TIGIT expression on peripheral blood and decidual CD8+ T cells in women with unexplained recurrent spontaneous abortion†.

The two-way communication between the mother and the fetus is accomplished by immune cells. CD8+ T cells of normal pregnant (NP) women express progesterone receptor (PR). Binding of PR to progesterone (P) and the production of progesterone-induced blocking factor (PIBF) can aid immune escape, which is an important factor in the maternal immune response. We detected the proportion of CD8+ T cells and the expression of the surface costimulatory molecules BTLA, TIGIT, ICOS, and PD-1 in peripheral blood and decidual tissues of women with unexplained recurrent spontaneous abortion (URSA) and in NP women. All patients were at 8 -10 weeks of gestation. The results showed that there was no change in the proportions of CD8+ T cells in peripheral blood and decidual tissues of URSA patients compared to those of NP women. In peripheral blood, compared with the NP group, the URSA group showed decreased expression of BTLA + CD8+ T cells and the difference was statistically significant, but there was no difference between the groups in terms of TIGIT + CD8+, PD-1 + CD8+, and ICOS + CD8+ T cells. There was no change in the levels of TIGIT + CD8+, PD-1 + CD8+, ICOS + CD8+, and BTLA + CD8+ T cells in decidual tissue. These data confirm that the number of CD8+ T cells in peripheral blood and decidual tissue is not the main factor leading to the pathogenesis of URSA, and other immune cells may play an important role in URSA, but this hypothesis needs further exploration and research.