Attempts to characterize the mechanisms involved in the growth inhibition of Mycobacterium microti in interferon-gamma or tumor necrosis factor-alpha activated J774A.1 cells.

The growth of Mycobacterium microti was inhibited within J774A.1 macrophage cells activated with either interferon-gamma or tumor necrosis factor-alpha. Activation with interferon-gamma or tumor necrosis factor-alpha alone did not stimulate the production of nitrite in J774A.1 cells. Interferon-gamma but not tumor necrosis factor-alpha increased the production of hydrogen peroxide in a concentration dependent manner but scavengers of reactive oxygen species did not influence the growth inhibiting effect of interferon-gamma within J774A.1 cells. Both interferon-gamma and tumor necrosis factor-alpha enhanced the fusion of M. microti containing phagosomes with lysosomes and the ultimate degradation of bacteria. Our results showed that growth inhibition of M. microti within interferon-gamma or tumor necrosis factor-alpha stimulated J774A.1 cells was independent of reactive oxygen intermediate and reactive nitrogen intermediate production.