Immunohistochemical and Morphometric Analysis of Intestinal Full-thickness Biopsy Samples from Cats with Lymphoplasmacytic Inflammatory Bowel Disease

SummaryThe distribution and numbers of CD3+ T lymphocytes, immunoglobulin+ plasma cells and calprotectin (L1)+ macrophages was analyzed in full-thickness, formalin-fixed biopsy samples from the small intestine (duodenum, jejunum and ileum) and from the colon from nine cats with clinical signs of inflammatory bowel disease (IBD). All animals had lymphoplasmacytic enteritis or lymphoplasmacytic enterocolitis. Equivalent samples from the same intestinal regions from 12 healthy pet cats served as controls. Labelled cells in the lamina propria were counted by computer-aided morphometry. The different cell types were similarly distributed in both groups, but there were differences in their numbers. There were more CD3+ T cells in the duodenum and jejunum of cats with IBD; however, the difference was only significant for the duodenum. There were significantly more IgA+ cells in the duodenal crypt region. There were significantly more IgG+ cells in the lower jejunal crypt region. Plasma cells expressing IgM were decreased in cats with IBD, but the difference was not significant. L1+ macrophages were significantly decreased in the lower crypt area of the colon in cats with IBD and there was a trend to decreased L1+ cells in the upper crypt area of the duodenum and jejunum. Comparison of the results of this study with previous findings on endoscopically-obtained duodenal biopsy samples from cats with IBD revealed some differences. These discrepancies might relate to differences between control cat populations, types of biopsy samples, methodological factors such as different counting techniques and the activity of the disease at the time of sampling.