The distribution of lymphocytes expressing αβ and γδ T-cell receptors, and the expression of mucosal addressin cell adhesion molecule-1 in the canine intestine

The present study defined the distribution of alpha beta and gamma delta T-cell subsets, and the expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in the intestinal tract of an outbred population of dogs with no evidence of gastrointestinal disease. A panel of monoclonal antibodies reactive with the canine alpha beta and gamma delta T-cell receptors (TCRs) and human MAdCAM-1 was used in a series of immunoperoxidase or immunofluorescence studies. alpha beta T cells were predominant within the villous lamina propria with a significantly decreasing linear trend from upper villus to crypt (P<0.0001). A proportion of intraepithelial lymphocytes (IELs) also expressed the alpha beta T-cell receptor, with significantly greater numbers in villous than in crypt epithelium (P<0.0001). However, there were no significant differences in the numbers of either lamina propria or epithelial alpha beta T cells between different intestinal regions, gamma delta T cells were rare in the lamina propria, but a prominent gamma delta IEL population was present and shown by double-colour immunofluorescence studies to be principally of the CD4(-)CD8 alpha(-) phenotype. MAdCAM-1 was expressed by endothelial cells in the mucosa, sub-mucosa and muscularis layers of all levels of the intestinal tract. In the mucosa, significantly more MAdCAM-1 positive endothelium was present in regions of crypt than villous lamina propria (P<0.0001), but there were no significant differences between expression in different intestinal regions. The quantitative and qualitative data will enable comparisons of these parameters to be made with those in dogs suffering from inflammatory bowel diseases. (C) 1999 Harcourt Publishers Ltd.