Immunohistology of Peyer's patches in the dog.

Canine Peyer's patches were examined by light microscopy and immunohistochemistry for possible variations depending on the location within the small intestine and for similarities and dissimilarities to PPs from other species. The duodenal and jejunal PPs were characterized by relatively large domes and interfollicular areas. In contrast, the ileal PP had small domes and poorly developed interfollicular areas and very large follicles. T cells were found in the interfollicular area and corona and in lesser numbers in the dome and germinal centers. The ileal PP contained far fewer T cells than the proximal PPs. Domes of canine PPs contained some cytoplasmic IgA+ (cIgA+) and many cIgG+ cells. Peanut agglutinin (PNA) stained germinal center cells in a selective but not-uniform way and did not stain T cells.