Dynamics of the interaction between Entamoeba histolytica and components of the immune response. III. Fate of antibodies after binding to the cell surface.

Binding to the surface of living E. histolytica trophozoites of 125I-labelled anti-amoeba antibodies or of such antibodies and antiglobulin resulted in a rapid disappearance of the antibody into the medium. This disappearance consisted of a rapid temperature-independent and a subsequent slow temperature-dependent phase. The disappearance of antibody from fixed trophozoites merely consisted of a temperature-independent rapid phase whereas no slow phase was observed. The magnitude of the rapid phase of antibody disappearance was virtually the same in living and fixed cells. During culture of living trophozoites for 4 h the amount of iodine-labelled material sedimenting lighter than monomeric IgG increased from 2% to 14% of all labelled material in the case of the single antibody layer. The corresponding values for the double layer were 2% and 32%. Of the material lighter than IgG, 10% of that in the single layer and 26% of that in the double layer were detected in the medium. Thus, during the 4-h culture period 25% of the originally amoeba-bound single layer of antibody probably disappeared from the cells not complexed with antigen, 27% disappeared as complexes heavier than IgG, 10% disappeared as material lighter than IgG, and 38% persisted on or within the cells. The corresponding values for the double layer of antibody were 10%, 30%, 26% and 34%.