SUPPRESSION OF HUMORAL IMMUNITY BY MONOCLONAL-ANTIBODY TO CD79B, AN INVARIANT COMPONENT OF ANTIGEN RECEPTORS ON B-LYMPHOCYTES

CD79b is an invariant component of antigen receptors on B lymphocytes. Previous data have suggested that monoclonal antibody (mAb) to CD79b would introduce negative signals into B lymphocytes and suppress humor al immunity. We tested this hypothesis in this study using in vitro as say systems, and revealed that anti-CD79b mAb effectively suppressed t he antibody response to a T-cell dependent antigen. The speculated mec hanisms for this immunosuppression were: (i) down-modulation of antige n receptors, (ii) inhibition of B lymphocyte differentiation, and (iii ) induction of B lymphocyte unresponsiveness. Of these three, we confi rmed that the first two were actually induced by anti-CD79b mAb treatm ent, whereas the in vitro system could not induce the unresponsiveness of B lymphocytes.