Effect of Con A - Treated Allogeneic Lymphocytes on the Mitogenic Response of Normal Human L ymphocytes

The functional role of suppressor cells in the control of the immune response has now been recognized. This phenomenon may soon be considered an essential aspect of immunity. The role of antigen-specific and nonspecific suppressor lymphocytes in the regulation of antibody production has been demonstrated (1). In vivo experiments have suggested the existence of suppressor cells in some forms of immunologic tolerance (2-5), chronic suppression of alloantibody production (6, 7), antigenic competition (8), and lymphocyte response to stimulation by thymus-independent antigens such as pneumococcal polysaccharide S-III (911). Suppressor cells have also been shown to be involved in the control of cellmediated immunity in animals (12). Furthermore, inhibition of graft-versushost reaction by suppressor cells has been demonstrated when thymocytes and spleen cells obtained from young NZB/W mice were transplanted to newborn C3H/He mice (13, 14). Mouse spleen cells incubated in vitro with the plant lectin, concanavalin A (Con A), 1 will develop suppressor activity in several assay systems. These Con A-activated suppressor cells can inhibit in vitro lymphocyte response to sheep red blood cells (15, 16), allogeneic antigens in mixed lymphocyte cultures (MLC) (17), and cell-mediated cytotoxicity (18). Recently, increasing evidence has accumulated that suppressor cells in the peripheral blood may be involved in the etiology and pathogenesis of such pathologic states as autoimmune disease in animals (14), and common variable hypogammaglobulinemia (19), Hodgkin's disease (20), and multiple myeloma in man (21). In this publication, we report the existence of a population of cells present in the peripheral blood of healthy human volunteers which can be induced by Con A to manifest suppressor functions and that this potential may indeed reflect a latent immunologic control.