In vivo and in vitro responses of cats sensitized with viable Mycobacterium bovis (BCG).

Cats were injected subcutaneously with viable Mycobacterium bovis (BCG), and immune responses were evaluated at various times after injection. The BCG injection produced fever, leukocytosis, neutrophilia, and lymphadenopathy of regional lymph nodes. Intradermal tuberculin injection produced responses consistent with delayed type hypersensitivity reaction in the treated cats at postinoculation day 21. Skin responses to tuberculin were not significant at postinoculation day 49. The cellular infiltrate at the tuberculin injection site at 48 hours after injection was an admixture of polymorphonuclear cells and mononuclear cells. The BCG produces strong intradermal skin responses in the cat, but the response was not long-lived as in cattle and guinea pigs. The BCG injection did not produce significant changes in the absolute total lymphocyte and absolute T-lymphocyte numbers in peripheral blood. The percentage of T-lymphocytes was significantly higher in the BCG-treated group. Differences were not observed in lymphocyte blastogenesis with tuberculin and non-specific mitogens between BCG-treated and control cats.