Analysis of the developmental stage of specific and nonspecific cytotoxicity. I. Separation of the developmental steps of specific cytotoxicity by susceptibility to irradiation

Susceptibility of T-cell-mediated cytotoxicity to x irradiation was examined in the stages of induction and expression. C3H/He mice and a methylcholanthrene-induced sarcoma of C57BL/6 origin were used for experiments. Established cytotoxicity was radioresistant. Irradiation of hosts before tumor inoculation suppressed induction of cytotoxicity. Irradiation at 3 hr after tumor inoculation or later did not affect induction of cytotoxicity. Cytotoxicity became detectable on day 7 but not on day 3, when mice were irradiated 3 hr after tumor inoculation. Tumor resection abolished cytotoxicity when carried out 24 hr after tumor inoculation but not when carried out on day 3 or later. Sonicated antigen of tumor cells proved to be effective in raising the radioresistant state in the hosts, since cytotoxicity was detectable in those given irradiation 3 hr and viable tumor cells 6 hr after the priming. The radioresistant nature of cytotoxicity may be acquired within a very short period after immunization. However, development of killer cells from such a radioresistant state requires further antigen stimulation with viable tumor cells for a limited period, and maturation of such cells requires some latent period thereafter