[Localization of Entamoeba histolytica antigens using IgA]

The presence of IgA anti-Entamoeba histolytica antibodies has been demonstrates in intestinal secretions and serum of human amebiasis. We investigated which are the cellular components of trophozoites that react with IgA anti-ameba antibodies from immune serum, colostrum and human milk. The cellular localization of such antigens was accomplished by an indirect immunoperoxidase technique using anti-human IgA (alpha chain specific) labeled with peroxidase, both for light and transmission electron microscopy. Intracellular antigens were localized after permeating the parasites with cold acetone (-10 degrees C) for 3 min. and cryosections of 1 micron thick. The antigens that react with IgA antibodies from immune serum, colostrum and human milk were located in the plasma membrane and the internal portion of some cytoplasmic vesicles. So far, it is unknown what is the biological function of IgA in human amebiasis but in other systems it protects against certain parasites.