Cell-mediated immunity to Friend virus-induced leukemia. II. Characteristics of primary cell-mediated cytotoxic response.

The primary cell-mediated cytotoxic response to a Friend virus-induced leukemia, FBL-3, in C57BL/6 mice was measured by the 125IUdR release assay. Intraperitoneal (i.p.) inoculation of 1 x 10(1) FBL-3 cells produced progressive tumor growth (progressors); subcutaneous (s.c.) inoculation of as many as 5 x 10(6) FBL-3 cells produced only transient tumor growth (regressors), and these mice would subsequently resist i.p. challenge of FBL-3 cells at 3 days after s.c. inoculation. The kinetics of the primary cell-mediated cytotoxic response of regressors was biphasic. Significant cytotoxicity could be detected at 3 to 5 days after s.c. inoculation of 5 x 10(6) FBL-3 cells peaked at days 10 to 14, declined to a very low level or became undetectable around days 20 to 30; then the reactivity reappeared and persisted at least up to 60 days. In progressors, the kinetics of the cell-mediated cytotoxic response was similar to the regressors, but the reactivity was much lower. The cytotoxic response was found to be T cell dependent, during both the first peak (days 10 to 14) and the second peak (days 40 to 60). In adoptive transfer experiments, lymphocytes from regressors gave 90% protection against i.p. challenge of FBL-3; lymphocytes from progressors only gave 40% protection.