In vivo and in vitro studies of the influence of the immune status of C3Hf-Bu mice on the effectiveness of local irradiation of a methylcholanthrene-induced fibrosarcoma.

normal, immunodepressed, or immunized recipients, respec tively. A tumor reached 12 mm in diameter more quickly when transplanted into immunized recipients than when transplanted into control animals. Also, the radiation dose that controlled one-half of the treated 12-mm tumors was about 1000 rads higher in immunized than in normal recipients. //; vitro studies showed that lymphoid cells from tumorous mice were effective in inhibiting colony formation by fibrosarcoma cells. The degree of inhibition of colony formation by the lymphocytes decreased according to the size of tumor borne by the lymphocytes donor. Also, lymphocytes collected from tumor-bearing donors were less effective if the donor had been immunized prior to transplantation. The most effective lymphoid cells came from preimmunized but non-tumorbearing donors. Serum from tumorous but not from immunized mice contained blocking antibodies, i.e., abolished inhibition of colony growth by lymphoid cells.