Subsets of circulating T-lymphocytes mediating resistance to in vivo growth of a carcinogen-induced syngeneic rat tumor.

Wistar rats immunized by s.c. implantation of irradiated Mc7 sarcoma tissue were resistant to the growth of a challenge of this chemical carcinogen-induced syngeneic tumor. Lymphocyte populations enriched in each of the two major T-cell lineages recognized by mouse monoclonal antibodies were prepared from the thoracic duct lymphocyte pool of tumor-resistant rats by affinity chromatography and infused i.v. into normal syngeneic rats. The recipients of either one donor equivalent of "helper" T-cells identified by the monoclonal antibody W3/25 or one donor equivalent of "nonhelper" T-cells identified by the monoclonal antibody OX-8 were resistant to a challenge of Mc7 sarcoma cells. Contaminating cells do not appear to account for the activities of each enriched population, indicating that lymphocytes contributing to expression of resistance to in vivo growth of Mc7 sarcoma must be present in both the helper and the nonhelper T-cell lineages. No direct cytotoxic activity by the thoracic duct lymphocyte populations against the Mc7 sarcoma cells could be demonstrated in vitro. These lymphocytes were generated in vivo and delivered to the systemic circulation of tumor-resistant hosts, implying they play a role in the expression of antitumor resistance in the intact immunized donor.