The effect of lymphokines on the ability of macrophages to protect mycobacteria from a bactericidal antibiotic.

Murine peritoneal macrophages protect Mycobacterium intracellular from amoxycillin added to the culture medium. This protective effect is enhanced by the addition of macrophage-activating lymphokines, although in the absence of amoxycillin these lymphokines cause macrophage-mediated inhibition of the organisms. Thus about 10 times more organisms survive exposure to 100 microgram/ml of amoxycillin for 3 days in the presence of lymphokine-activated macrophages than in their absence, whereas without amoxycillin the reverse is true. These findings suggest that in this in vitro system lymphokines cause stasis rather than kill of the organisms. The possibility that lymphokine-induced bacteriostasis protects mycobacteria from antibiotics in vivo is discussed.