IL-12 and IFN-γ in host defense against mycobacteria and salmonella in mice and men

The development of gene-knockout mice and the identification of gene-deficient humans have improved our understanding of the role of IL-12 and IFN-γ in host defense. Comparison of experimental and natural infections has shown that animals and humans genetically deficient in immunity mediated by IL-12 or IFN-γ are highly susceptible to mycobacteria and salmonella. Impaired secretion of, or response to, IFN-γ is the common pathogenic mechanism that accounts for impaired granuloma formation and uncontrolled growth of bacteria within macrophages. The axis formed between IL-12 and IFN-γ is essential for protective immunity against mycobacteria and salmonella in mice and men.