[Differential growth inhibition of mycobacteria by interferon-gamma-or tumor necrosis factor-alpha-treated murine peritoneal macrophages].

Growth inhibition of the intracellular mycobacteria such as Mycobacterium tuberculosis, M. bovis, M. kansasii, M. avium, M. intracellulare, M. fortuitum, and M. chelonae subsp. abscessus by interferon-gamma (IFN-gamma)- or tumor necrosis factor-alpha (TNF-alpha)-treated murine peritoneal macrophages elicited by proteose peptone was studied in vitro. Macrophages were infected with slowly growing mycobacteria and the extracellular mycobacteria were washed out. Then, macrophages were treated with IFN-gamma or TNF-alpha at a concentration of 10 to 1000 U/ml for 2 days. In another experiment, macrophages were pretreated with these cytokines for 1 day then infected with rapidly growing mycobacteria as before. Macrophages were cultured with or without IFN-gamma or TNF-alpha for additional day. Mycobacterial growth was assessed by determination of colony-forming units on 7H11 agar plates after destruction of the macrophages. Stimulation of macrophages with IFN-gamma reduced the growth of mycobacteria. However, except for M. tuberculosis and M. bovis, growth was not inhibited by macrophages treated with TNF-alpha. IFN-gamma seems to be an important cytokine for the activation of mycobactericidal mechanisms in murine macrophages. Stimulation with IFN-gamma or TNF-alpha and subsequent phagocytosis of M. tuberculosis or M. intracellulare increased O2- production, which was assayed by the method of cytochrome C reduction by murine peritoneal macrophages. Phorbol myristate acetate-triggered-O2- production was also elevated by the cytokine pretreatment of the macrophages, suggesting that mycobacterial growth inhibition did not parallel the production of reactive oxygen intermediates in TNF alpha-activated murine peritoneal macrophages. These data suggest that bactericidal mechanisms of murine macrophages against nontuberculous mycobacteria may not depend on reactive oxygen intermediates.