A Placenta‐Derived Suppressor Factor with a T‐Cell Bias

Raghupathy R, Khan SFB, Syamasundar PV, Bansal P, Azizieh F. A placenta‐derived suppressor factor with a T‐cell bias. AJRI 1999; 42:205–218 © Munksgaard, Copenhagen PROBLEM: Functional and mechanistic aspects of immunosuppression by murine placental supernatants (MPS) were investigated. METHOD OF STUDY: MPS and a low molecular weight fraction of the supernatant (MPSf) were tested for suppressive action on T‐cell reactivity in vitro and in vivo, on B‐cell responses and on T‐cell activation events. RESULTS: MPS and MPSf suppress mitogen‐induced proliferation and mixed lymphocyte reactions of human and murine lymphocytes, antigen‐induced proliferation of T cells in vitro and in vivo, proliferation of CD8+ lymphocytes, proliferation induced by cross‐linking of surface CD3 and the in vivo response of mice to allogeneic stimuli. MPSf affects cell cycling of activated T cells and blocks interleukin (IL)‐2 production. MPSf does not affect antibody production or the induction of MHC class II expression on B cells. CONCLUSIONS: MPSf is a potent inhibitor of T‐cell responses in vitro and in vivo, with no demonstrable effect on B‐cell function.