Interaction between Entamoeba histolytica and human polymorphonuclear neutrophils.

The interaction of human polymorphonuclear neutrophils (PMNs) with two strains of Entamoeba histolytica that exhibit different degrees of "virulence" was examined in animal and tissue culture systems. PMNs actively migrated toward both strains of amoebae. Less virulent amoebae (strain 303) were surrounded by PMNs (greater than or equal to 300/amoeba), fragmented and ingested by PMNs by means that appeared to be independent of oxygen. In contrast, contact with virulent amoebae (HM1) caused loss of PMN motility, PMN degranulation, death, and occasional phagocytosis by the amoebae, which survived concentrations of greater than 1,000 PMNs/amoeba. PMNs that did not directly contact virulent amoebae remained alive and active. At least two separate components of cytopathogenicity by virulent amoebae were observed: first, extracellular, contact-dependent, serum-independent cytolysis that was dependent on intact microfilament function; and second, amoeba phagocytosis of human PMNs. This contact-dependent ability of virulent amoebae to kill and phagocytize host neutrophils may be important in their pathogenic capacity.