Inflammation induced by a glycolipid fraction from Mycobacterium leprae

1. The inflammatory properties of a glycolipid fraction isolated from human recovered Mycobacterium leprae were investigated. The inflammatory reaction induced in mouse lung by the inoculation of the glycolipid fraction adsorbed to charcoal particles was characterized by a large influx of macrophages at various stages of maturation and of epithelioid cells around the particles. 2. When injected as an aqueous emulsion into the footpad of mice, the same fraction evoked a dose-dependent massive influx of mononuclear (MN) cells. The inflammatory reaction reached a peak at 6 days. The minimal effective dose of glycolipid was 0.1 micrograms. 3. The kinetics of inflammatory cell migration was studied by total and differential counts of leucocytes that migrated to the peritoneal cavity of mice inoculated intraperitoneally with the glycolipid fraction. This fraction initially induced intense polymorphonuclear (PMN) migration, which was later reduced, with a simultaneous increase in MN cells. 4. Adherent peritoneal cells (APC) incubated with glycolipid released one or more soluble factor(s) which induce active PMN and MN cell chemotaxis in vivo as well as in vitro. Thus, the MN cells may be attracted to the site of glycolipid inoculation by factor(s) released through the interaction of macrophages with the glycolipid fraction. 5. The present results demonstrate that a glycolipid containing trehalose and mycolic acid isolated from M. leprae reproduces some aspects of the fundamental lesion of leprosy.