Interactions of Mycobacterium lepraemurium with resident peritoneal macrophages; phagocytosis and stimulation of the oxidative burst.

Live Mycobacterium lepraemurium or 60Co-gamma-irradiated organisms stimulated a very weak oxidative burst compared with similar numbers of heat-killed organisms or with live M. microti. This was found to reflect the poor uptake of the living organisms rather than an absolute failure to stimulate an oxidative burst. It is possible, however, that phagocytosis of fewer than 3-4 bacteria may not trigger the respiratory burst. Pre-incubating live M. lepraemurium with sera from infected mice, but not with fresh normal mouse sera, resulted in enhanced phagocytosis with a concomitant increase in the oxidative burst. The level of opsonic activity correlated with the M. lepraemurium specific antibody titres. The opsonic activity appeared to be mediated by antigen-antibody activation of the classical complement pathway as heat-inactivation destroyed the activity.