Role of suppressor cells in antibody-induced inhibition of mixed lymphocyte reactions.

Facilitating immune sera (FIS) have both in vivo enhancing and in vitro blocking properties. They inhibit the mixed lymphocyte reaction (MLR) in the mouse. In the present report, we studied the inhibitory capacity of these sera after removal of populations of suppressor cells both in vivo by adult thymectomy and in vitro by depletion of histamine-receptor-bearing cells (HRC). A significant decrease of the MLR inhibition by FIS after either of these depletions was observed. It appeared therfore that facilitating antibodies and thymus-dependant and/or HRC could cooperate in the antibody-induced inhibition of the MLR in the mouse.