Serum proteins in the plasma membrane of Entamoeba histolytica

The ability of axenic Entamoeba histolytica, strain 200:NIH, to adsorb serum proteins was studied. Amebae were grown in Diamond's TPS-1 medium. Serological reactivity was observed between the plasma membrane of E. histolytica and rabbit anti-bovine or anti-human serum when the amebae were grown, respectively, with bovine or human serum. Antisera were obtained from rabbits immunized with culture medium, amebal homogenates, and various amebal subcellular fractions: soluble phase, microsomal fraction, and a large vesicle fraction. The presence of serum proteins was demonstrated in the large vesicle fraction by the double diffusion and indirect hemagglutination tests. Immunofluorescence (IF) studies on amebae grown in bovine or human serum showed the surface amebae exhibited IF with specific antibodies against the serum in which they were grown. Rabbit anti-human serum blocked IF on the surface of amebae grown with human serum. From these data we conclude that the plasma membrane of in vitro grown E. histolytica can adsorb human and bovine serum proteins.