Crypt hyperplasia related to increased lymphocyte activation in the rectal mucosa of children with ulcerative colitis.

The presence of cells positive for interleukin-2 receptors (CD25) and the proportion of Ki-67 positive dividing cells in the crypts were studied with monoclonal antibodies using sensitive immunohistochemical techniques in the rectal biopsy specimens taken from 13 children with inflammatory bowel disease (4 Crohn's disease and 9 ulcerative colitis) and 10 controls. In all specimens, but one, from patients CD25+ cells were found in the surface and crypt epithelium, while in none of controls were seen such cells. The mean percentage of dividing crypt cells was significantly higher in ulcerative colitis (36.0%) and in Crohn's disease (34.6%) than in controls (18.4) (p < 0.001 in both comparisons). In ulcerative colitis, a correlation between CD25/CD3 ratios in the surface and crypt epithelium and the percentage of dividing crypt cells was found. We conclude that activated lymphocytes have a role in the crypt hyperplasia of ulcerative colitis.