Abstract

C3HeB/FeJ peritoneal exudate macrophages elicited with a variety of sterile inflammatory agents or with Mycobacterium bovis strain BCG were exposed to Leishmania tropica amastigotes in vitro. The percentages of L. tropica-infected macrophages were similar in resident and inflammatory macrophage populations over 72 hours in culture. Inflammatory macrophages supported intracellular replication of L. tropica in excess of that by resident macrophages. These macrophages also failed to demonstrate cytotoxicity to tumor cells in vitro, a defined nonspecific effector function of activated macrophages. However, macrophages from BCG-treated mice were significantly more resistant to initial infection with L. tropica, killed intracellular amastigotes by 72 hours in culture and were cytotoxic to tumor cells, indicating full immunologic activation. The inability of inflammatory macrophages to kill L. tropica parasites suggests that inflammation may actually contribute to the pathogenesis of leishmaniasis.