Ubiquitous expression of HLA-DR antigens on human small intestinal epithelium

To clarify the frequency of the expression of HLA-DR antigens on the human small intestinal epithelium and the variation of such expression, 43 specimens (duodenum 16, jejunum 8, ileum 19; histologically normal 33, pathologic lesions 10) were studied for HLA-DR expression by indirect immunoperoxidase staining using monoclonal antibodies against HLA-DR antigens. All specimens reacted with anti-HLA-DR antibodies with minor variations. Most specimens showed decreasing intensity from the top of the villi toward the base of the villi and no staining in the crypt. In about half of the specimens, clear peripheral and cytoplasmic staining of the epithelial cells was observed. In some cases, the staining of the apical portion of the epithelium was patchy. The expression was unrelated to the lymph follicle. This ubiquitous expression of HLA-DR antigens on the small intestinal epithelium presents a striking contrast to an absence of the antigens on the normal large intestinal epithelium. A preliminary study on the pathologic lesions demonstrated the following changes in the expression of HLA-DR antigens; appearance of HLA-DR antigens on the crypt epithelium in Crohn's disease, loss of HLA-DR antigens on the epithelium covering the area of cell infiltration in macroglobulinemia and covering adenoma in familial polyposis coli.