IMMUNOHISTOCHEMICAL IDENTIFICATION OF THE CELLS PARASITIZED BY 2ND-GENERATION SCHIZONTS OF EIMERIA-TENELLA

Conflicting reports exist in the literature concerning the type of cel ls within the lamina propria of the ceca that harbor second-generation schizonts of Eimeria tenella. Most of the previous studies concerning these cells have been performed using routine light or electron micro scopy. Consequently, difficulties are evident in precise definition of the type of these cells using normal morphological criteria, since gr owth of the schizonts of E. tenella alters the morphology of the paras itized cell, making it difficult to recognize the cell type. This has led us to investigate the possibility of precisely identifying the sub epithelial cells that are parasitized by mature schizonts. For this pu rpose we used cytoskeletal markers, namely, keratin and vimentin inter mediate filaments, which allow the discrimination between epithelial a nd mesenchymal cells. Localization of keratin and vimentin on frozen c ecal sections was studied immunohistochemically using specific monoclo nal antibodies. Sites of antigenicity were detected by the avidin-biot in complex (ABC) immunoperoxidase technique and visualized by the depo sition of diaminobenzidine. The identity of the cells was confirmed by the immunodetection of keratin intermediate filaments in the cytoplas m of the cells. Immunoreactivity for vimentin was absent in the parasi tized cells. Therefore, we conclude that the development of second-gen eration schizonts of E. tenella takes place in epithelial cells within the lamina propria. which are presumably crypt epithelial cells that leave the crypts and enter the lamina propria after infection by first -generation merozoites.