Lymphocyte subpopulations and mast cells intestinal changes as indicators of inflammatory bowel disease in dogs

Inflammatory bowel disease (IBD) is a disease with recurring gastrointestinal symptoms. Lymphocytes and mast cells are proposed as important components in the immunopathology of IBD in dogs. Mast cells depend on degranulation, a process that compromises mucosal permeability and normal intestinal barrier function, which alters the normal inflammatory process by allowing recruitment of lymphocytes in dogs with IBD. In this study, T and B lymphocyte populations and mast cells were examined in situ in 39 intestinal samples of dogs affected by IBD, by immunohistochemistry. Both T lymphocytes and mast cells numbers were significantly higher in the lamina propria of the intestinal wall of dogs with IBD compared with control dogs. Out of the total number of mast cells detected by CD117 expression significantly less cells appear to be granulated according to granule staining with Toluidine Blue, suggesting that an important degranulation process takes place in IBD. Single and double immune staining for tryptase and chymase showed that mast cells can express only one or both enzymes. Tryptase positive cells were significantly higher in number that chymase positive and tryptase/chymase positive cells. T lymphocytes were concentrated mostly at the upper portion of the intestinal villi lamina propria while mast cells were distributed mainly among crypts. These results suggest that populations of T lymphocytes and mast cells play a role in the immunopathology and development of IBD in dogs, also these changes could be helpful as complementary indicators of canine IBD.