Generation of a phagocytosis-stimulating factor by polymorphonuclear neutrophils during phagocytosis.

Polymorphonuclear neutrophils (PMNs) generated a phagocytosis-stimulating factor (PSF) intracellularly during phagocytosis of opsonized zymosan or latex particles. The generation of PSF by PMNs reached the maximum at 60 min after the start of phagocytosis. When PSF was washed out after preincubation with PMNs or opsonized zymosan particles, no enhancement of phagocytosis by PMNs was observed, suggesting that the continuous existence of PSF in the incubation medium is required for stimulation of phagocytosis.