Endoglin Regulates Intercellular Interactions between Trophoblast and Natural Killer Cells

Abstract

The interaction of natural killer and trophoblast cells underlies maternal-fetal immune tolerance. The data on the participation of endoglin (ENG, CD105), or its soluble form, in the regulation of the communication of these cells are currently insufficient. In this study, we have investigated the role of endoglin in the intercellular interactions between natural killer cells and trophoblasts. Here, we show that NK-92 cells and JEG-3 cells constitutively express MICA/B, and CD105. In the presence of JEG-3 cells, the expression of NKG2D, CD94, MICA/B, and CD105 by NK-92 cells was increased, and the number of NK-92 cells expressing NKG2A, CD94, and MICA was reduced. Antibodies against ENG and recombinant endoglin (rENG), attenuated the trophoblasts’ influence and returned the phenotype of the NK-92 cells to that of cells found in monoculture conditions. The antibodies and rENG also increased the expression of pSMAD2/3 by NK cells in both monoculture and co-culture conditions. The antibodies increased the trophoblasts’ sensitivity to the cytotoxic effect of NK cells. In general, our findings indicate a significant role of endoglin in the intercellular communication between NK cells and trophoblasts. We also speculate that endoglin forms a complex with TGFβ, which aids in TGFβ trafficking between these cells.