A Flow Cytometric Assay Reveals an Enhancement of Phagocytosis by Platelet Activating Factor in Murine Peritoneal Macrophages

Phagocytosis of fluorescein isothiocyanate-labeled latex beads by peritoneal macrophages from thioglycollate-stimulated mice was examined in vitro by means of flow cytometry. This assay revealed that platelet activating factor (PAF), a known inflammatory mediator, enhanced the phagocytosis in a dose-dependent manner. The enhancement was completely suppressed by a PAF antagonist, Y-24180, and partly suppressed by another antagonist, CV-3988. The phagocytosis of both nonstimulated and PAF-stimulated macrophages was suppressed in Ca2+-free ethylene glycol bis(β-aminoethyl ether) N, N′ -tetraacetic acid-containing solution, but the phagocytosis was enhanced by PAF even in this solution. These results suggest that phagocytosis by macrophages is enhanced by PAF in allergic and inflammatory reactions.