Immunomodulatory properties of monoclonal anti-Thy-1.2 antibody in vivo.

Monoclonal mouse anti-Thy-1.2 antibody of IgG3 isotype (MTA) inhibits in a significant and long-term manner the regional graft-versus-host reaction (GVHR) when administered to donors as well as to recipients. The process of sensitization in the reaction of delayed type hypersensitivity to SRBC (DTH) is, on the other hand, suppressed only if MTA is administered immediately prior to sensitization. If the time interval between the injection of MTA and of SRBC is extended, the resulting DTH is stimulated. Similarly, the titers of total Ig against SRBC are decreased only if MTA is administered shortly before immunization. Contrasting effects of MTA on the production of IgM and IgG were observed. While the production of IgG was inhibited even after the time interval between the administration of MTA and immunization had been increased, the production of IgM antibodies was stimulated. In recipients of allogeneic Sarcoma I treated with MTA, the primary growth of the tumor is enhanced and the percentage of permanent progressors is increased. Mechanisms of MTA activity are discussed.