 One potential reason for early inactivation of the system is that the immunosuppressive effect of these glycoproteins may be so complete that their continued leakage into the circulatory system could lead to a global suppression of the maternal immune response, compromising the mother's ability to carry the fetus to term.Human sperm and eggs also lack molecules for the immune recognition of "self".These immune markers are also known as major histocompatibility complex (MHC) antigens or more specifically in humans as human leukocyte antigens (HLA)).