Bidirectional regulation between 1st trimester HTR8/SVneo trophoblast cells and in vitro differentiated Th17/Treg cells suggest a fetal-maternal regulatory loop in human pregnancy.

HTR8/SVneo cells regulated maternal CD4+ T-cell differentiation, resulting in the expansion of immunosuppressive Treg cells, while CD4+ T cells might promote the growth, and control the invasiveness of HTR8/SVneo cells. Thus, a bidirectional regulatory loop might exist between trophoblasts and maternal immune cell subsets, thereby promoting harmonious maternal-fetal crosstalk.