Growth of sarcoma 180 in normal and splenectomized BALB/c mice immunized with BCG

An evaluation was made on the growth of Sarcoma 180 (S 180) in normal and splenectomized BALB/c mice which had been immunized 40 days before the tumor challenge with BCG, either intradermally or in diffusion chambers placed in the peritoneal cavity. Immunization with intradermal BCG did not modify the growth of subcutaneous S 180, whereas it provided significant protection when the tumor was inoculated with BCG. Previous treatment with BCG in diffusion chambers had no effect on the development of S 180, but significantly decreased the percentage of survival of mice inoculated with S 180 mixed with BCG, as compared to the homologous group immunized with intradermal BCG. Splenectomy performed before the challenge with S 180, enabled 56% of mice lacking previous immunization to survive and increased this percentage to 100% when the tumor was inoculated mixed with BCG. As for splenectomized mice immunized with BCG within diffusion chambers and challenged with S 180, there was 90% of survival and 69% in those challenged with S 180 mixed with BCG. These results would suggest that the action of BCG on the growth of S 180 differs according to whether the mycobacteria are in direct contact with the host or exert their effect by means of soluble antigens capable of passing through the millipore filter of the diffusion chambers. These effects would be conditioned by the immunological state of the host.