Immunogenic strength of sarcomas induced by methylcholanthrene in millipore filter diffusion chambers.

Normal BALB/c fibroblasts enclosed in two-compartment diffusion chambers with a methylcholanthrene (MCA) disc were left in the peritoneal cavity of BALB/c mice or were incubated in vitro for 4 to 24 weeks while protected from the immunoselective process. This protection was demonstrated by the fact that cells of a BALB/c sarcoma induced by MCA, which were immunogenic when injected s.c., were unable to sensitize when grown for 2 weeks within 0.22-/im filter diffusion chambers placed in the peritoneal cavity of syngeneic mice. The chambers with the fibroblasts exposed to MCA were recovered and opened at 4-week intervals; their contents were implanted s.c. into immunodepressed syngeneic or semisyngeneic mice. In 41 to 63% of the cases, the in vivo and in vitro diffusion chamber cultures gave rise to sarcomas. When the diffusion chambers were made with 1.2-¿¿m, lymphocytepermeable filters and were kept in vivo, only 10% of the cultures produced tumors. Fifty tumors were tested for immunogenicity by transplantation methods and 45 were found to be immunogenic. The immunogenic strength, however, showed a large variability without any correlation with the latent period, length of exposure to the carcinogen, or growth rate. We concluded that an immunological control operates during MCA carcinogenesis but that other factors influence the immunogenic strength of these sarcomas.