Immunochemical studies of the surface and cytoplasmic membranes of Entamoeba invadens (Rodhain 1934).

The antigenic properties of cell fractions prepared from axenically grown Entamoeba invadens were investigated using various immunoelectrophoretic methods. All membrane fractions displayed varying degrees of antigenicity, the most predominant being a cytoplasmic light-vesicle fraction. The surface membrane showed the least diversified range of antigenic components and was also the least immunogenic fraction as judged by the reactivity of the antisera produced. Using tandem-crossed immunoelectrophoresis the antigenic profiles of the membrane fractions were compared. No evidence was obtained for the presence of either lipid or carbohydrate in the antigenic moieties of any of the membrane fractions. Using a series of sequential solvent extractions it was concluded that both divalent metallochelate linkages and interiorly located hydrophobic associations were principally involved in binding the major antigenic components within the light-vesicle membrane. An enzymic function was assigned to certain of the membrane antigens, the immunoprecipitates obtained showing both acid phosphohydrolase and non-specific esterase acitivity toward a variety of substrates.