Modulation of phagosome-lysosome fusion in mouse macrophages

A previously described fluorescence assay has been used to characterize factors that modulate phagosome-lysosome (P-L) fusion in mouse macrophages. Fusion was not affected by enzymatic modification or by concanavalin A cross-linking of the plasma membrane or by coating the phagocytic particle with concanavalin A or immune serum. Pretreatment of cells with 10^-5-10^-4M colchicine, or treatment immediately after ingestion with 1-10μg/ml cytochalasin did not alter P-L fusion; implying that the cytoskeleton does not control fusion in a rate-limiting way. Fusion was strikingly elevated in 5 hr cultures of activated macrophages from immune-boosted mice. A lower enhancement was seen in cells activated by proteose-peptone, a nonspecific inflammatory agent.