Immune enhancers composed of polyvalent binding sites of anti-CD3 antibodies.

Anti-CD3 antibodies of some IgG subclasses are very potent T lymphocyte mitogens in vitro and, seemingly contradictorily, very effective immunosuppressive agents in vivo. Using hamster anti-murine CD3 monoclonal antibody, 2C11, as a model, we have found that 2C11.IgG, or its F(ab')2 fragment, coupled to microbeads can provide short-term and vigorous activation of T cells and expansion of the lymphoid system in vivo. In contrast to free 2C11.IgG, these conjugates do not kill mice and cause T cell depletion, and can enhance immune responses. This study suggests that properly modified anti-CD3 antibodies can serve as in vivo immune system enhancers potentially useful in the treatment of cancer and chronic infectious diseases.