The murine leukemia L1210‐specific cytotoxic T‐cell clone K7 was established by repeated antigenic stimulation of spleen cells of L1210‐immune CD2F, mice in long‐term culture. K7 possessed L1210‐specific cytolytic activity detectable by the 51Cr‐release test, but lost its cytolytic activity about 100 days after initiation of culture (designated as clone K7L). Clone K7L retained its L1210‐specific tumor‐growth‐inhibitory activity independently of culture supplementation with IL‐2. K7L possessed the cell‐surface antigenic phenotype of cytotoxic T cells, Thy‐1+, Lyt‐1+, Lyt‐2+. This clone K7L displayed surprisingly strong activity in specifically inhibiting In vivo tumor growth of L1210 by day 5 in the peritoneal cavity of CD2F1 mice when injected together with 105 tumor cells (more than 90% inhibition at E/T = 5), and prolonged survival times of most of the mice for more than 60 days, whereas control mice inoculated with L1210 alone died on day 9–17. This unique in vivo anti‐tumor activity was not correlated to the In vitro cytolytic activity. Nevertheless, bystander inhibitory effect on the growth of third‐party tumor cells (P388) was not seen in mice injected with a mixture of L1210 and P388 together with K7L, suggesting that K7L inhibited L1210 growth by direct cell‐to‐cell interaction. Host cells such as X‐irradiation (800R)‐sensitive lymphocytes and Carrageenan‐sensitive macrophages were not involved in the early growth inhibition of L1210 by K7L.
All Science Journal Classification (ASJC) codes
- Cancer Research