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 an
d in vivo, on B-cell responses and on T-cell activation events.
RESULTS: MPS and MPSf suppress mitogen-induced proliferation and mixed lymp
hocyte reactions of human and murine lymphocytes, antigen-induced prolifera
tion of T cells in vitro and in vivo, proliferation of CD8(+) lymphocytes,
proliferation induced by cross-linking of surface CD3 and the in vivo respo
nse of mice to allogeneic stimuli. MPSf affects cell cycling of activated T
cells and blocks interleukin (IL)-2 production. MPSf does not affect antib
ody 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.