Dynamics of the interaction between Entamoeba histolytica and components of the immune response

Trophozoites of Entamoeba histolytica redistributed specific antibodies reacting to antigens on their surface. The presence of a second layer of anti-antibodies enhanced the redistribution of anti-amoeba antibodies but was not a prerequisite for this process. Microfluorometric measurements of the fluorescence intensity in different areas of the cell surface provided objective evidence for the antibody-induced redistribution. In order to distinguish surface-bound and internalized anti-amoeba antibodies, the trophozoites were fixed in PFA. This fixation made the cells impermeable to antibodies. Thus, after fixation in PFA at different times during the redistribution process surface-bound anti-amoeba antibodies labelled with one fluorochrome could be detected with anti-bodies labelled with another fluorochrome. This approach showed that the amoeba, in addition to the redistribution, also internalized anti-amoeba antibodies.