ENHANCED PHAGOCYTOSIS AND INTRACELLULAR KILLING OF CANDIDA-ALBICANS BY GM-CSF-ACTIVATED HUMAN NEUTROPHILS

Little is known about effector cell modulation regarding phagocytosis and candidacidal activities of human neutrophils in response to granulocyte-macrophage colony stimulating factor (GM-CSF). In neutrophil monolayer assays, pre-treatment of cells with ultrapure GM-CSF at 40 Units ml-1 for a minimum of 1 h showed a significant enhancement of phagocytosis of Candida albicans (phagocytic index of 2.6 compared with 1.6 for unactivated neutrophils) after a 20 min ingestion period (P < 0.001). By counting viable colonies 50% of intracellular yeast cells were killed by non-activated neutrophils following internalization for 2 h. Neutrophils activated for 2 h with 40 Units ml-1 of GM-CSF killed 90% of intracellular blastoconidia (P < 0.02). These results demonstrate that in in vitro assays GM-CSF enhances phagocytosis and intracellular killing of C. albicans.