Killing of Aspergillus spores depends on the anatomical source of the macrophage.

To resolve the controversy over the capacity of macrophages to kill or inhibit germination of Aspergillus spores, we compared this function in peritoneal and alveolar macrophages. Alveolar macrophages from rabbits killed 82 to 90% and completely digested 72 to 82% of spores of Aspergillus fumigatus in 30 h. In contrast, peritoneal macrophages could not even inhibit the germination of ingested spores; more than 85% transformed into mycelia within 24 h. Killing by alveolar macrophages was delayed for 3 to 6 h after phagocytosis and was independent of oxidative killing mechanisms and immune activation. The ability of alveolar macrophages to kill Aspergillus spores without modulation by T lymphocytes or the generation of oxygen intermediates points out that concepts built on studies of peritoneal macrophages may be misleading and underscores the importance of studying the role of macrophages in immunity with cells from the appropriate anatomical site.