Ultrastructural localization of antigenic sites on sporozoites, sporocysts, and oocysts of Eimeria acervulina and Eimeria tenella by monoclonal IgG and IgM antibodies.

Immunoelectron microscopy was used to study the localization of monoclonal IgG (13.9 and 15.84) and IgM (10.84) antibodies generated against Eimeria tenella sporozoites on sporozoites, sporocysts, and oocysts of Eimeria acervulina and E. tenella. A uniform layer of ferritin was present on sporozoites of E. tenella fixed chemically before the addition of 10.84, 13.90, or 15.84 (called prefixed), whereas postfixed (fixed chemically after exposure to monoclonal antibody) sporozoites lacked ferritin, indicating that the latter had capped immune complexes. Patches of ferritin were present on prefixed and postfixed sporozoites of E. acervulina exposed to 15.84, indicating that immune complexes containing 15.84 were not capped. Sporocysts of E. tenella exposed to 10.84 had a uniform layer of ferritin on their outer surface; ferritin was localized in patches on those exposed to 13.90 or 15.84. In E. acervulina sporocysts exposed to 15.84, ferritin was widely scattered on the outer surface but formed a uniform layer on the inner surface of the sporocyst wall. Patches of ferritin occurred on the inner layer of the oocyst walls of E. tenella and E. acervulina exposed to 10.84, 13.90, or 15.84. These findings indicate the shared antigen detected by 15.84 differed in relative amount, spatial distribution, and structural location in sporozoites and sporocysts of E. acervulina and E. tenella.