IMMUNOHISTOCHEMICAL CHARACTERIZATION OF IMMUNOGLOBULIN-CONTAINING CELLS AND T-CELLS IN THE COLONIC MUCOSA OF HEALTHY DOGS

Objectives-To quantitate numbers of immunoglobulin (Ig)-containing cel ls (IgA, IgG, and IgM) and T cells (CD3+, CD4+, and CD8+) in the colon ic mucosa of healthy dogs, and to determine whether mean cell numbers differ among colonic regions. Animals-10 clinically normal young adult mixed-breed dogs. Procedure-Endoscopically obtained specimens of asce nding, transverse, and descending colonic mucosa were stained specific ally for IgA, IgG, and IgM heavy chains and T-cell antigens, CD3+, CD4 +, and CD8+, using immunoperoxidase techniques. Morphometric analysis, performed by light microscopy, was used to quantitate numbers in thes e standardized areas of colonic mucosa. Data analysis allowed determin ation of mean cell numbers in each colonic region, as well as comparis on of mean cell numbers among colonic regions. Results-The CD3+ and CD 8+ T cells were the predominant immune cell types in ail colonic regio ns. In the mucosa, CD3+ T cells were significantly (P < 0.05) more num erous than CD8+ T cells, and CD8+ T cells were significantly (P < 0.05 ) more numerous than CD4+ T cells. The IgA-containing cells were signi ficantly (P < 0.05) more numerous than IgG-containing cells, whereas I gM-containing cells were least numerous (P < 0.05). Differences in mea n cell counts among colonic regions were not significant for Ig-contai ning cells or T cells. Conclusions-Mean numbers of immune cells did no t differ significantly among colonic regions in healthy dogs, although differences existed in mean populations of T cells and Ig-containing cells. The CD3+ and CD8+ T cells were the most numerous immune cell ty pes in colonic mucosa. Clinical Relevance-These quantitative data prov ide a basis for study of alterations in populations of mucosal immune cells and their possible contribution to the pathogenesis of gastroint estinal tract disease.