Anatomical location of phosphorylcholine and other antigens on encysted Trichinella using immunohistochemistry followed by Wheatley's trichrome stain.

This work investigated the location on the parasite of Trichinella antigens recognized by the mouse immune system and the question as to which of them bear the epitope phosphorylcholine (PC). Wheatley's trichrome stain (initially developed for faecal smears) proved to be excellent for visualization of Trichinella structures, enabling four types of stichocyte to be distinguished. By applying this stain on infected muscle sections after immunocytochemistry using (a) anti-PC BH8 monoclonal antibodies, (b) serum from mice that had been infected twice in the presence of 0.05% thiabendazole (to prevent reproduction by adult females) and then bled on day 7 post-reinfection, (c) serum from infected mice that were bled on day 14 postinfection, or (d) serum from infected mice that were bled on day 42 postinfection, we found (1) that PC is an abundant structural epitope on the hypodermis/muscle, genital primordium and intestinal tract but is absent from the cuticle and stichosome; (2) that the principle secretory cells of adult worms are delta- and beta-stichocytes, whereas those of migrating and encysted L1 larvae are alpha-stichocytes; and (3) that Trichinella antigens recognized in the encysted phase of the parasite's life cycle are present in parasitized myofibres in the sarcoplasmic matrix and in the nucleoplasm of hypertrophic nuclei. The significance of these findings is discussed.