Human Amebic Dysentery

Electron Microscopy of Entamoeba histolytica Contacting, Ingesting, and Digesting Inflammatory Cells

Joe L. GriffinArmed Forces Institute of Pathology, Washington, D. C. 20305

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Biopsy samples from human cases of amebiasis were studied by electron microscopy. Numerous inflammatory cells passed through flattened or damaged epithelium into the colonic lumen. Polymorphonuclear leucocytes, eosinophils, and lymphocytes were eaten and digested by amebae, as in the well-known ingestion of red blood cells. Ingested inflammatory cells have apparently not been recognized because one of the first changes, preceding loss of external membranes in food vacuoles, is loss of nuclear affinity for stain. Inflammatory cell ingestion seems to be characteristic of amebae causing human dysentery. Inflammatory cells do not effectively limit amebic activities and may even contribute to host damage. Cytotoxic materials could be released directly by lysis of uneaten cells or might pass through the amebae and be released (possibly altered) from excretory vacuoles.

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