Macrophage-mediated fungistasis in vitro: requirements for intracellular and extracellular XXXX .

@entity19 @entity375 @entity1327 @entity137
Macrophage @entity137 for @entity1327 was investigated by culturing @entity19 peritoneal macrophages with a thin-capsuled clone of @entity1327 under conditions permitting efficient phagocytosis. @entity375 replication was quantitated by electronic particle counting after detergent lysis of macrophages, and viability was determined by quantitative plate counts. Under appropriate conditions, reproduction was completely inhibited; stasis began at 2 hr after addition of @entity375 and lasted for 30 hr. During this time organisms in medium alone proliferated rapidly, doubling their number every 2.5 hr. After removal from macrophages, 60 to 100% of macrophage-inhibited cryptococci formed colonies, indicating that the cytotoxic effect was primarily fungistatic. When @entity375 cells were removed from macrophages, replication recommenced within 5 hr. Supernatant medium from fungistatic co-cultures was not inhibitory for fresh @entity375 cells. Conditions required for complete fungistasis were 1) peritoneal macrophages induced by peptone from BCG-infected @entity19 , 2) endotoxin in nanogram per milliliter range added to serum-containing cell culture medium, 3) confluent macrophage monolayers, and 4) macrophage:cryptococci ratios of 20 to 100:1. Fungistasis occurred without phagocytosis but was more efficient when cryptococci were engulfed. For efficient fungistasis, macrophages must differentiate to and be maintained in the activated state. These results with @entity375 cells agree with the known requirements for macrophage effector function against neoplastic target cells.
