Macrophage function in Mycobacterium lepraemurium infection: morphological and functional changes of peritoneal and splenic macrophages in vitro.

Morphological and functional changes in peritoneal macrophages (PM) and splenic macrophages (SM) from mice infected with Mycobacterium lepraemurium were investigated. A decrease in the number but an increase in the size of PM were observed during the infection. PM were vacuolated, and a small proportion of them were observed in cell division. They demonstrated greater ability to adhere and spread in vitro, enhanced phagocytosis of immunoglobulin G (IgG) and IgM erythrocytes, and greater phagocytosis and killing of Candida sp., when compared with normal resident PM. In contrast, parasitized SM demonstrated significantly reduced phagocytic ability, whereas heavily parasitized SM neither spread nor phagocytosed Candida sp. The random migration and chemotactic responsiveness of PM from infected animals were also enhanced. These results indicated the persistent activation of PM but the suppression of some activities of SM during M. lepraemurium infection.