An immunohistological study of phenotypic characteristics of cells of the inflammatory response in the intestine of Schistosoma bovis-infected goats

The cellular inflammatory response in the small intestine of 21 gears infec ted with Schistosoma bovis was phenotypically characterized by immunohistoc hemistry between 6 and 32 weeks post-exposure, with particular reference to perioval granulomatous reactions. Macrophages of granulomas consistently e xpressed MHC class II molecules, whereas multinucleated giant cells in gene ral did not. Most granulomas contained moderate infiltrates of CD2+ (CD4+ o r CD8+) and gamma/delta (T19(+)) T cells, whereas B lymphocytes were sparse . Intact extravascular mucosal eggs, lacking appreciable cellular reactivit y on plain histopathology, displayed surrounding collars of MHC class II+ m acrophages. Gamma/delta T cells and MHC class II+ macrophages were the pred ominant cell types in perivascular inflammatory cell clusters in the submuc osa. The phenotypic cellular composition of granulomas did not change appre ciably with duration of infection. The results indicate the importance of M HC class II-restricted immune events in the caprine S. bovis egg granulomas and also suggest a role of gamma/delta T cells in their pathogenesis. It i s hypothesized that the early appearance of perioval macrophage collars may serve to protect eggs from ovicidal host defence mechanisms, facilitating excretion and continuation of the life-cycle.