Mycobacterium tuberculosis H37Ra and H37Rv Differential Growth and Cytokine/Chemokine Induction in Murine Macrophages In Vitro

The role of tumor necrosis factor-α (TNF-α) in controlling growth of Mycobacterium tuberculosis in murine peritoneal macrophages infected in vitro was studied. TNF-α was shown to be required but not sufficient, and the amount of TNF-α produced by the infected cells did not correlate with the extent of growth control. In this system, TNF-α-dependent control of growth of the avirulent strain H37Ra was independent of inducible nitric oxide synthase (iNOS) and interferon-γ (IFN-γ), as shown by the infection of macrophages from selected gene-disrupted mice. TNF-α-mediated bacteriostasis of H37Ra in the infected macrophages was associated with increased expression of selected Th1-type cytokines and chemokines. In contrast, growth of the virulent strain H37Rv in macrophages involved upregulation by infected cells of Th2-type cytokines, including interleukin-5 (IL-5), IL-10, and IL-13. Taken together, these results suggest that the particular nature of macrophage activation and the cytokine and chemokine response to infection with different M. tuberculosis strains determine the ability of the cells to control the growth of the intracellular bacilli.