[The role of HLA-G expression in the embryo during implantation].

HLA-G is a non-classical major histocompatibility complex class I molecule, whose tissue distribution is mainly restricted to the placenta. HLA-G expression in the placenta is found mainly in extravillous cytotrophoblast that invades décidual tissue and maternal spiral arteries as well as villous cytotrophoblast (soluble form). Its function contributes to modulate local placental immunity during pregnancy: it is an immunosuppressive molecule inducing apoptosis of activated CD8(+) T cells and down-modulating CD4(+) T cell proliferation. HLA-G also modulates cytokine secretion of NK cells upon interaction with specific receptors. Soluble HLA-G1 may also contribute to the control of implantation.