Immunosuppressor factor(s) produced by decidua-associated suppressor cells: a proposed mechanism for fetal allograft survival.

Mechanisms that explain failure of rejection of the antigenic fetus by the mother appear to lie at the fetomaternal interface. Successful pregnancies have been correlated with the presence of decidua-associated suppressor cells. Supernatants from these cells were tested for their ability to suppress the proliferation of interleukin 2-dependent cells and were also subjected to high-performance liquid chromatography. Decidual supernatant was found to have peak suppressive activity at two molecular weights (43,000 and 21,000 daltons). The activity of decidual supernatant was directed specifically at interleukin 2-dependent cells and interfered with interleukin 2 action. The importance of this mechanism in graft rejection is well known. Decidual supernatant may thus prevent fetal allograft rejection by preventing the maternal cytotoxic effectors from receiving the interleukin 2-dependent help that they need to proliferate and remain actively cytolytic.