5. The placenta and tissues of the developing fetus are almost
devoid of MHC class I and II molecules. but instead have HLA-E and
-G genes which inhibit maternal uterine NK cells from attacking.
6. Some placental cells express FasL, so that activated T cells can be
killed before fetal tissues are attacked. Fetal cells also express the
RCA proteins DAF and MCP that can interfere with maternal
complement activation.