Differences in resistance of C57BL/6 and C57BL/10 mice to infection by Mycobacterium avium are independent of gamma interferon

After infection with a low-virulence strain of Mycobacterium avium, C57BL/6 and C57BL/10 mice had clear differences in the control of the infection in their livers and spleens. This difference in susceptibility was not associated with differences in the H-2 complex. It was dependent on the activity of CD4⁺ T cells but unrelated to the ability of these cells to secrete gamma interferon or to the development of delayed-type hypersensitivity responses at 3 weeks of infection. It was associated with lower total numbers of CD4⁺ cells present in infected spleens and was related to an earlier induction of protective T cells, as measured by adoptive-transfer assays. These data further strengthen the notion of gamma- interferon-independent mechanisms of protection against mycobacteria.