Surface redistribution and release of antibody-induced caps in entamoebae.

Polyspecific antibodies bound to Entamoeba induced surface redistribution of membrane components toward the uroid region. Capping of surface antigens was obtained with a single layer of antibodies in E. histolytica and E. invadens. This surface segregation progressed to a large accumulation of folded plasma membrane that extruded as a defined vesicular cap. A spontaneous release of the cap at the end of the capping process took place. These released caps contained most of the antibodies that originally bound to the whole cell surface. Two-thirds of radiolabeled antibodies bound to the surface of E. histolytica were released into the medium in 2 h. Successive capping induced by repeated exposure of E. invadens to antibodies produced conglomerates of folded surface membrane, visualized as stacked caps, in proportion to the number of antibody exposures. These results indicate the remarkable ability of Entamoeba to rapidly regenerate substantial amounts of plasma membbrane. The properties of surface redistribution, liberation of caps, and plasma membrane regeneration, may contribute to the survival of the parasite in the host during infection.