THE DISTRIBUTION OF DIVIDING T-CELLS THROUGHOUT THE INTESTINAL WALL IN INFLAMMATORY BOWEL-DISEASE (IBD)

T cell hypersensitivity has been implicated in the tissue damage in Cr ohn's disease (CD). All studies to date have examined mucosal T cells, although much of the tissue damage occurs in the submucosa and muscle layers. The aim of this work was to study T cell proliferation throug hout the intestinal wall in children with IBD. Surgical resection mate rial from 19 children with CD (10 ileal, 10 colonic), seven with ulcer ative colitis (UC), and 12 normal controls was studied. The distributi on of dividing T cells was investigated by double-immunohistochemistry using Ki67 to identify proliferating cells, and CD3 to identify T cel ls. In ileal and colonic lamina propria virtually no Ki67(+), CD3(+) c ells were seen in control, UC or CD tissue. In contrast, there were si gnificantly more Ki67(+), CD3(+) cells within the lymphoid follicles, of ileal and colonic CD than in the follicles in UC and controls. Incr eased numbers of Ki67(+), CD3(+) cells were present in the submucosa, muscle layers (M) and serosa in Crohn's ileitis and colitis compared w ith the lamina propria (LP), although only in the muscle of the colon was the difference statistically significant (LP, 0.4% (0-1%), M, 1.6% (0-5.2%); P = 0.03). Pooling data from ileal and colonic CD, however, did show significantly increased Ki67(+), CD3(+) cells in both serosa and muscle layers compared with the LP. Dividing T cells have been id entified in the deeper layers of the gut wall in CD. These may contrib ute to the fibrosis and muscle hyperplasia characteristic of the condi tion.