Antigens prepared from trophozoites of Entamoeba histolytica (DKB strain), the room-temperature strains Laredo and Huff, E. moshkovskii (FIC strain), and E. invadens (PZ and SivL strains) were made to react against human anti-E. histolytica serum and rabbit anti-DKB and anti-PZ serum in indirect-hemagglutination and immunodiffusion tests. Control experiments (which all gave negative results) consisted in testing positive antiserum against the antigen prepared from penicillin-inhibited Bacteroides symbiosus (the culture associate of amebae) and against the components of the culture medium.
Immunoelectrophoretic analysis of the antigens indirectly confirmed the results of the immunodiffusion tests and demonstrated that the bands that showed reactions of partial identity had curvatures different from those of their counterparts, while having identical or similar electrophoretic mobilities.
In general it was found that all the strains of Entamoeba studied have common antigenic moieties. More precise results should be obtained when the antigens are fractionated and the fractions are tested independently.