Tim-3/CTLA-4 pathways regulate decidual immune cells-extravillous trophoblasts interaction by IL-4 and IL-10.

To obtain a successful pregnancy, the establishment of maternal-fetal tolerance and successful placentation are required to be established. Disruption of this immune balance and/or inadequate placental perfusion is believed to be associated with a lot of pregnancy-related complications, such as recurrent spontaneous abortion, pre-eclampsia, and fetal intrauterine growth restriction. Extravillous trophoblasts (EVTs) have the unique ability to instruct decidual immune cells (DICs) to develop a regulatory phenotype for fetal tolerance. Utilizing immortalized human first trimester extravillous trophoblast cells and primary EVTs, we found that DICs promote EVT function and placental development. We have previously shown that checkpoints T-cell immunoglobulin mucin-3 (Tim-3) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) are important for DIC function. In the present study, we showed that blockade of Tim-3 and CTLA-4 pathways leaded to the abnormal DICs-EVTs interaction, poor placental development, and increased fetal loss. Treatment with IL-4 and IL-10 could rescue the adverse effects of targeting Tim-3 and CTLA-4 on the pregnancy outcome. Hence, the reproductive safety must be a criterion considered in the assessment of immuno-therapeutic agents. In addition, IL-4 and IL-10 may represent novel therapeutic strategies to prevent pregnancy loss induced by checkpoint inhibition.