Histological observations on the intestinal immune response towards horseradish peroxidase in rats

The intestine immune response in rats following immunization with horseradish peroxidase (HRP) was studied morphologically. Various routes of immunization (intraperitoneal, intravenous, intraenteric and intra-Peyer's patch) were tested. Single injections did not evoke any specific antibody-containing (anti-HRP) cells in Peyers' patches (PP) and lamina propria of the small intestine. Only an intraperitoneal or intraenteric booster injection following intraperitoneal priming induced the formation of anti-HRP cells in PP and lamina propria. In the initial period of the immune response most of the anti-HRP cells were blast cells which were located mainly within the thymus-dependent interfollicular area of PP. Later on in the immune response more than 90% of the anti-HRP cells were located in the lamina propria of the villi and had the morphology of plasma cells.