LYMPHOCYTE-MEDIATED CYTOTOXICITY AGAINST TUMOR-CELLS .2. CHARACTERISTICS AND TISSUE DISTRIBUTION OF CONCANAVALIN A-ACTIVATED CYTOTOXIC EFFECTOR CELLS

In vivo or in vitro activation of cytotoxic effector [mouse] lymphocytes by concanavalin A (Con A) occurred in a population of effector cells exhibiting a degree of immunological specificity when Con A was present during the cytotoxic assay. In this communication, the Con A-activated effector cell was characterized by physical criteria, and an attempt was made to assign it to a given subpopulation of thymus-derived [T] lymphocytes. Macrophages played no role in target cell [YAC mouse leukemia cells] lysis in this system, nor was their presence required for Con A activation of the effector cell. The effector cell proved insensitive to anti-.theta. serum, but was classified as a T cell by the enrichment of cytotoxicity when a purified population of T cells was activated by Con A in vitro, and by the failure to activate the effector cell in nude mice. Precursors of the effector cell resided primarily in the spleen, were radioresistant up to 400 R and were short-lived after adult thymectomy. The effector cell can be classified with the T1 population of T cells and has similar characteristics to a cytolytically active cell previously described.