FIGURE 9.

Proposed model for crosstalk between embryo trophoblasts and decidual leukocyte subsets at the maternal–fetal interface in human first-trimester pregnancy. TSLP secreted by human trophoblasts instructs dDCs and then induces generation of decidual CD4⁺CD25⁺FOXP3⁺ Tregs in early pregnancy. These cells in turn inhibit proliferation and IFN-γ secretion from CD4⁺CD25⁻ T cells and increase invasiveness and HLA-G expression in trophoblasts. These alterations decrease cytotoxicity of decidual CD56^brightCD16⁻ NK cells and increase expression of inhibitory cytokines. This interactive crosstalk between trophoblasts and decidual leukocytes contributes to maternal immunotolerance toward fetal Ags and placentation.