Phagocytosis of Acanthamoeba by macrophages and neutrophils and "kiss and run" evasion by Entamoeba histolytica.

Human macrophages and neutrophils efficiently phagocytose Acanthamoeba polyphaga and Vermamoeba vermiformis in a phosphoinositide 3-kinase–dependent manner, overturning the “too large” dogma.

• Why it matters: Amoebae cause over 100 million severe infections annually, yet it was long assumed that eukaryotic amoebae cannot be phagocytosed, leaving innate immune limits unclear.
• What they did: The study tested phagocytosis by human macrophages and neutrophils and found it depends on phosphoinositide 3-kinase activity; it also compared live versus formalin-killed or UV-irradiated Entamoeba histolytica.
• The result: Entamoeba histolytica evades phagocytosis via a “kiss and run” strategy, whereas killed or UV-irradiated forms are efficiently phagocytosed, with macrophages forming F-actin fibrillar projections.

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