Immune response to ultraviolet-induced tumors. III. Analysis of cloned lymphocyte populations exhibiting antitumor activity.

Previously, we hypothesized that natural killer lymphocytes could function as effector cells in the rejection of UV-induced tumors in tumor-immune animals. Immunization with progressor UV-tumor 2237 induced lymphocytes exhibiting natural cell-mediated cytotoxicity but failed to elicit tumor-specific cytolytic T lymphocytes. In the present investigation, T lymphocyte cloning technology provided a means of isolating homogeneous lymphocyte populations exhibiting CTL and NK activities. Clones with both CTL and NK activity were isolated from regressor-1316-immune mice, but NK-like clones only were isolated from progressor-2237-immune mice. An evaluation of the in situ anti-UV-tumor action of a representative NK lymphocyte clone revealed that these cells could in fact prevent tumor outgrowth, supporting our hypothesis that these cells could function as effector cells in UV-tumor rejection responses in tumor-immune animals.