Early pregnancy human decidua gamma/delta T cells exhibit tissue resident and specific functional characteristics

A successful pregnancy is a complicated process that builds upon two aspects of the maternal immune system that need to be balanced. As one of the indispensable groups of immune cell at the maternal-fetal interface, the decidual gamma/delta (γδ) T cells have attracted research attention in normal pregnancy and miscarriage. However, the role of γδ T cells in fetal growth remains poorly understood. Here, we found that the γδ T-cell population resident in decidua during early pregnancy was enriched and secreted growth factors including growth differentiation factor 15 and bone morphogenetic protein 1. A diminution in such growth factors may impair fetal development and result in fetal growth restriction. We also observed that early decidual γδ T cells exhibited stronger cytokine-secretion characteristics, but that their cytotoxic actions against A549 cells were weaker, compared with γδ T cells in peripheral blood mononuclear cells (PBMCs). In addition, the functional abilities of early decidual γδ T cells in promoting trophoblast cell proliferation, migration, invasion and tube formation were also significantly more robust than in γδ T cells of PBMCs. These findings highlight the importance of γδ T cells in fetal growth and maternal immunotolerance during pregnancy and show that they differ from γδ T cells in PBMCs. We thus recommend additional investigation in this research area to further elucidate a role for γδ T cells in pregnancy.