Plasma-dependent chemotaxis of macrophages towards mycobacterium tuberculosis and other organisms

Heat-killed whole cells of Mycobacterium tuberculosis activate normal fresh guinea-pig plasma so that a chemotactic factor which attracts guinea-pig macrophages is produced. This factor differs from that generated by Shigella flexneri endotoxin. Mycobacteria attract macrophages more strongly than neutrophils, while endotoxin attracts both types of cell strongly, but is more active for neutrophils than for macrophages. The activity of the mycobacterial cytotaxigen is found in several protein fractions and in other fractions extracted from whole organisms or culture filtrates and is still present after lipid has been removed from the bacterial cells. The capacity of M. tuberculosis to activate macrophage chemotaxis in plasma is dependent on a heat-labile factor in plasma and is abolished by treatment of the plasma with several complement inhibitors.