Quantitative assessment of mast cells and expression of IgE protein and mRNA for IgE and interleukin 4 in the gastrointestinal tract of healthy dogs and dogs with inflammatory bowel disease

Objective-To characterize the mucosal IgE network in dogs affected with inf lammatory bowel disease (IBD) and compare it with that for healthy dogs. Animals-9 healthy dogs and 20 dogs with IBD. Procedure-In situ hybridization of mRNA specific for IgE and interleukin 4 (IL-4) and immunohistochemical analysis for IgE protein and 2 markers of ma st cells (ie, tryptase and chymase) were performed on tissue sections obtai ned from the gastrointestinal (GI) tract and lymph nodes of dogs. Results-Dogs with IBD had significantly more cells positive for IgE protein and more mast cells in the GI mucosa than healthy dogs. Despite this signi ficant increase in number of cells positive for IgE, cells positive for IgE mRNA were rarely detected in the GI mucosa; most cells positive for IgE mR NA were found in mesenteric lymph nodes. Signal pattern of IL-4 mRNA was si milar to that of IgE mRNA. Conclusions and Clinical Relevance-The increased numbers of cells positive for IgE and mast cells in dogs with IBD suggest hypersensitivity such as hy persensitivity to bacterial or dietary-derived antigens in the intestinal l umen. Future studies need to elucidate whether this represents a cause of i nflammation or is a result of the inflammatory process of IBD.