Recruitment of Effector T Lymphocytes Against a Tumor Allograft by T Lymphocytes Sensitized In Vitro2

Abstract

To study tumor allograft rejection mediated by lymphoid cells, we developed a system in which lymphocytes were sensitized in vitro and their antitumor activity was tested in vivo. Normal thymus lymphocytes were sensitized in vitro against allogeneic fibroblasts, then were separated from the sensitizing fibroblasts and injected into the footpads of syngeneic mice. The popliteal lymph node enlarged and developed effector cells that specifically rejected a tumor allograft. This resistance appeared to result from in vitro sensitization of the donor lymphocytes, Since injection of alloantigens could not induce resistance in the recipient mice. Using irradiation of either the sensitized donor lymphocytes or the recipient mice, we found that the effector cells were not the clonal descendants of the sensitized lymphocytes but were recruited by them within the recipient mouse lymph nodes. Mice that were thymectomized, irradiated, and reconstituted with bone marrow were used to study the origin of the participating lymphocytes, and we found that both recrultor and recruited lymphocytes were thymus-dependent T cells. Thus it appeared that interaction between two populations of T cells occurred during the tumor allograft response.