The Influence of Specific Antibodies and Complement on the Motility and the Viability of Entamoeba Histolytica Trophozoites

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Abstract
The distribution of peroxidase-labeled normal or specific rabbit immunoglobulin (Ig) in Entamoeba histolytica trophozoites was studied by transmission electron microscopy. Small amounts of normal Ig became attached to the cell surface but did not redistribute. Internalized specific Ig was firmly bound to the inner membranes of phagocytosis vacuoles, while aggregates of normal Ig were dispersed over the vacuolar lumen. The distribution of fluorescein isothiocyanate-labeled Ig in living amebae was correlated with the cell motility at different times. Immobilization coincided with the cellular metabolic processing of internalized material. Remobilization occurred when the Ig was degraded and antibodies again bound to the reappearing surface antigens. E. histolytica activated complement by the classical pathway. Fresh guinea pig serum alone did not produce lysis which, however, did occur when it was added together with normal rabbit Ig. Normal rabbit Ig may constitute a complement-fixing substrate and activate complement by the classical pathway. Immobilization of the amebae by cytochalasin B (10 µg/ml) increased the susceptibility to cytolytic effects of specific antibodies or complement, or both. Pharmacological inhibition of cell motility might augment the immunological defence of the host against amebic infection.