Tumor biopsy cells participating in systems in which cytotoxicity of lymphocytes is generated. Autologous and allogeneic studies

Freshly separated tumor cells from sarcomas and carcinomas were used in various roles in lymphocyte‐target cell interaction assays. They were poorer allogeneic stimulators than lymphocytes. They were however good allotargets for the cytotoxicity generated in mixed lymphocyte cultures. They were also killed as third party targets by lymphocytes activated in MLC. In a proportion of experiments, lymphocytes activated in MLC killed autologous tumor cells. Autotumor killer effect was generated in the majority of mixed cultures containing lymphocytes and tumor biopsy cells from the same individual. Generation of cytotoxicity against K562 was a good measure of lymphocyte activation and could be used as a sensitive indicator for the occurrence of the recognition step in the mixed cultures. We propose that for the search of lymphocytes with specific receptors, activation is a more reliable parameter than specific cytotoxicity since the latter function is also influenced by the sensitivity of the target. The results confirmed that patients with carcinomas and sarcomas possess autotumor‐reactive lymphocytes. These can be activated for cytotoxicity by in vitro confrontation with the tumor cells and occasionally through stimulation which is unrelated to the tumor cells.