[Mode of action of a soluble restricted factor, a suppressor of the allogeneic proliferative response in man].

Appearance of "suppressor cells" is induced by in vitro hyperimmunization of lymphocytes against allogeneic cells, incompatible for one HLA-DR antigen. These "suppressor cells under certain conditions, release in the culture medium, "suppressor factors" of the in vitro allogeneic proliferative response in Man. They are not immunoglobulins and act in a non specific way towards the stimulators. Only one of them is restricted to some individuals. This is shown when either responders or stimulators are incubated for different periods, with the "suppressor factors" prior to the primary mixed lymphocyte reaction (MLRI). The beneficial effect of transfusions on kidney graft survival, could be, in part, explained by a suppressor mechanism, analogous to the one described in vitro.