In vivo immunomodulation by monoclonal anti-L3T4. 1. Effects on humoral and cell-mediated immune response.

The in vivo administration of monoclonal anti-L3T4 antibody has been shown to be an effective preventative and, in some cases, therapeutic treatment for several murine models of autoimmune disease. This report deals with the effect of such treatments on humoral and cell-mediated responses to T-dependent antigens. Both the primary and secondary IgG responses to tetanus toxoid were inhibited when anti-L3T4 was administered prior to immunization, but it was ineffective in modulating an ongoing IgG response. Cell-mediated immunity, as detected by in vitro antigen-specific proliferative responses, was inhibited only if anti-L3T4 was given prior to immunization. It was not effective if treatment was delayed until 48 hr prior to lymph node harvest even though greater than 90% of L3T4+ lymph node cells were depleted by this treatment. The refractory behavior of the lymph node cells to anti-L3T4 treatment was not exhibited by antigen-primed cells obtained from peripheral blood or spleen. The importance of these findings with regard to antibody therapy for chronic autoimmune disease is discussed.