Effect of mouse anti-I region antiserum and complement on human mononuclear cell response to concanavalin A

Pretreatment of human peripheral blood mononuclear cells with mouse anti-Ia serum and complement was found to inhibit the subsequent T cell proliferative response to Con A. The cells from each individual tested were inhibited, regardless of DR allospecificity. Inhibition of Con A response by mouse anti-Ia antibodies and C was found to be due to elimination of adherent accessory cells (monocytes) rather than T cells. Anti-Ia serum appeared to recognize an essential subpopulation of human monocytes bearing cross-reactive antigens, since not all monocytes treated with anti-Ia serum and C were lysed. The use of highly restricted mouse anti-Ia serum demonstrated that the required monocyte population expressed antigens recognized by antibodies with activity to I-Ek products (Ia specificities Ia.7 and Ia.22). The required monocyte subpopulation was also recognized by a monoclonal antibody specific for Ia.7. Mouse anti-I-Ek alloantiserum or monoclonal anti-Ia.7 antibodies may be important tools with which to study human monocytes, and for further characterization of DR determinant requirements for monocyte-antigen presentation and monocyte-T cell interactions.