Phenotypic Identification of Specific and Nonspecific Suppressor T-Cell Populations Involved in the in Vivo Response to Alloantigen

The monoclonal antibody 984.D4.6 (ma984) has been previously shown to recognize antigen-specific suppressor T-cells in an in vitro alloantigenic mixed-lymphocyte response system. In addition, an antiserum generated in rabbits to the N-terminal sequence of the nonspecific suppressor factor SIRS (soluble immune response suppressor) has been shown to block the suppressive activity of nonspecific, concanavalin A-activated suppressor cells. In the present studies we have used these antibodies to investigate the development of T-suppressor activity in mice immunized with alloantigen. These studies demonstrate the development of two populations of suppressor cells, one of which is antigen nonspecific and inhibitable with anti-SIRS and a second that is antigen-specific and sensitive to removal by lysis with ma984 plus complement. These populations of suppressor cells arise well after the peak of cytolytic T-cell activity in response to alloantigen indicating asynchrony in the development of the immune response to alloantigen.