BACTERIOSTATIC ACTIVITY OF BCG PPD-ACTIVATED MACROPHAGES AGAINST MYCOBACTERIUM-FORTUITUM DOES NOT INVOLVE REACTIVE NITROGEN OR OXYGEN INTERMEDIATES/

Mycobacteria preferentially reside in resident macrophages whereas act ivated macrophages are presumed to eliminate the bacteria effectively. The aim of the present study was to determine the antibacterial activ ities of resident and activated murine peritoneal macrophages against Mycobacterium fortuitum and the intracellular mechanisms involved. Aft er phagocytosis M. fortuitum could not be killed by either BCG/PPD-act ivated and IFN-gamma-activated macrophages and resident macrophages. T he mycobacteria did not multiply in BCG/PPD-activated macrophages and the rate of proliferation of M. fortuitum in IFN-gamma-activated macro phages was only slightly inhibited compared to that in resident macrop hages. Experiments with selective inhibitors of the production of reac tive nitrogen intermediates (RNI) and reactive oxygen intermediates (R OI) demonstrated that these factors are not essential for the mycobact eriostatic activity of BCG/PPD-activated macrophages. After phagocytos is of M. fortuitum, BCG/PPD-activated and IFN-gamma-activated macropha ges produced substantial amounts of both RNI and ROI. No correlation w as found between the levels of these intermediates and the proliferati on of M. fortuitum in the macrophages. In conclusion, BCG/PPD-activate d macrophages are bacteriostatic, but not bacteriocidal for M. fortuit um and the former does not involve reactive nitrogen and oxygen interm ediates.