Comparison of the effects of anti-Thy-1.2 monoclonal antibody and xenogeneic antithymocyte serum on the development of SaI tumor allograft in mice.

Using the model of Sarcoma I (SaI) (H-2a) tumor allograft transplanted to normal B10 (H-2b) mice and to B10 mice pretreated with ATS, we studied the effects of anti-Thy-1,2 monoclonal antibody (MTA) and compared them with those of rabbit polyvalent antiserum against mouse thymocytes (ATS). When administered shortly before tumor transplantation, MTA showed immunosuppressive effects, at one dose identical to those of ATS, at two doses exceeding ATS effects. In the period following the transplantation of SaI to normal mice, single doses of MTA and ATS showed weak antitumor effects. In mice immunosuppressed with ATS before the tumor transplantation the effects of each agent differed: MTA showed opposite immunomodulatory effects depending on the period of its administration, while ATS supported the primary growth of tumors independent of the time of administration. The results indicate that the immunomodulatory influence of MTA on the development of the tumor allograft is more selective than that of ATS.