Alloantigen and microbial antigen-induced cellular immune responses: inhibitory effects of four anti-HLA class II monoclonal antibodies.

Four monoclonal antibodies (MAb's) directed against different epitopes of class II structures coded for by the human major histocompatibility complex (HLA), were studied to evaluate the relevance of these molecules on the control of different in vitro cell-mediated immune responses. Irrespective of the epitopes recognized, all MAb's tested exerted a powerful inhibitory effect on mixed lymphocyte cultures and on proliferation induced by microbial antigens. The generation of cytotoxic T lymphocytes and natural killer-like effectors also were inhibited by the addition of anti-HLA class II MAb in the cultures. The anti-HLA class II MAb provide a useful tool for the study of the in vitro immune response and eventually for therapeutic immunomodulation.