Role of cytokines in implantation and maintenance of pregnancy

Abstract The starting point of reproductive immunology is the understanding of the immunological mechanism for maintenance of pregnancy; why the fetus, which is a semi-allograft for the mother, is not rejected by the maternal immune system. Since Medawar pointed out this immunological contradiction in 1953, many investigators have addressed this question. As a result, we are coming to understand that not only a mere immunological tolerance but also immunotrophism, by which the immune system recognizes the fetal antigen actively, is important for the formation and maintenance of pregnancy. In addition, we are also coming to understand the importance of cytokines such as LIF and the cytokine environment of Th2 dominant. However, the cellular and microbiological mechanisms of these cytokines in the reproductive phenomenon are not well known. It is considered that the understanding of these mechanisms is useful for the clinical application to infertility or habitual abortion.