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

The present study defined the distribution of alphabeta and gammadelta 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 alphabeta and gammadelta T-cell receptors (TCRs) and human MAdCAM-1 was used in a series of immunoperoxidase or immunofluorescence studies. alphabeta 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 alphabeta 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 alphabeta T cells between different intestinal regions. gammadelta T cells were rare in the lamina propria, but a prominent gammadelta IEL population was present and shown by double-colour immunofluorescence studies to be principally of the CD4(&)minus;CD8alpha(&)minus; 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.