Development of protective immunity against bacterial and viral infections in tumor-bearing mice coincident with suppression of tumor immunity.

This report addresses the question whether Meth A (methylcholanthrene-induced fibrosarcoma) tumor bearing Balb/c mice are able to develop specific antimicrobial immunity. Although specific suppressor T lymphocytes appeared during tumor growth which prevented expression of antitumor immunity, the development of protective immunity to L monocytogenes, S. pneumoniae or ectromelia virus infections was unimpaired. The Meth A tumor produced a soluble immunosuppressive factor which inhibited lymphocyte and macrophage functions in vitro. Tumor growth failed to inhibit the formation of immunoglobulin essential to antipneumococcal immunity, or the development of a specific acquired cellular resistance of primary importance in immunity to listeria and ectromelia virus infections. That tumor growth did not interfere with the development of cell mediated immunity was demonstrated by the effective transfer of antilisteria immunity by immune spleen from tumor-bearing mice.