 These observations were made following the introduction of modern assisted reproduction technologies involving unrelated donor eggs and the use of "in vitro" fertilization (IVF).The eu-FEDS hypothesis was itself proposed to describe the precise immunological mechanisms that mediate protection of the developing eutherian fetus from the immune responses of its mother.The basic premise of the eu-FEDS hypothesis is that both soluble and cell surface associated glycoproteins, present in the reproductive system and expressed on gametes, suppress any potential immune responses, and inhibit rejection of the fetus.