Changes in distribution of Ia antigen on epithelium of the jejunum and ileum in rats infected with Nippostrongylus brasiliensis

This study compared the tissue distribution and cellular expression of Ia antigen in jejunal and ileal epithelium at various stages of intestinal inflammation produced by infecting rats with the nematode parasite Nippostrongylus brasiliensis. Tissues were examined at Day 0 (control), Day 4 (early), Day 10 (acute), and Day 16 (recovering). Frozen sections were stained with the MRC OX-4 anti-Ia monoclonal antibody using an immunoperoxidase technique. Control jejunal sections demonstrated positive epithelial Ia expression mainly in the mid-regions of the villi. The stain appeared to be mostly intracellular in the supranuclear area; the basolateral membrane stained faintly. At Day 4, a greater percentage of the epithelial cells expressed Ia, including those at the tips of the villi. The Day 10 sections demonstrated no staining at all of villus enterocytes, but the crypt epithelium was Ia positive. At Day 16, the pattern of Ia expression was similar to that seen in the early infection. In the ileum, stain was present in enterocytes over most of the villus and crypt regions except in the villus-crypt junction and did not change significantly during infection. We conclude that the changes in the expression of Ia antigen by intestinal epithelium are local to the site of infection and probably occur as a consequence of the host's inflammatory response.