Effects of C5a on baboon alveolar macrophage migration.

The effect of C5a, a fragment of the fifth complement component, on alveolar macrophage migration was studied using a micropore method. Cells were obtained by broncho-pulmonary lavage, in vivo or in vitro, from control baboons and baboons taught to smoke cigarettes. Macrophage migration directly depended on the C5a concentration cells encountered. The highest C5a concentrations studied enhanced migration more than 20-fold. Cells from smokers exhibited greater migration than those from nonsmokers, and cells recovered in vivo exhibited greater migration than in vitro cells, but these differences were not significant. A gradient analysis suggested that C5a-induced migration was chemotactic, i.e., oriented; C5a enhanced migration more than N-formyl-methionyl-phenylalanine, and C5a without the C-terminal arginine lost over two thirds of its capacity to enhance migration. The observation that C5a induces alveolar macrophage chemotaxis established that alveolar macrophages are similar to other mononuclear phagocytes with respect to C5a-enhanced migratory responses, and demonstrated that complement components may participate in lung inflammatory reactions through effects on cells other than neutrophils.