Leucocyte typing, cytokine expression, and epithelial turnover in the ileal pouch in patients with ulcerative colitis and familial adenomatous polyposis.

BACKGROUND/AIMS Conventional histopathology, leucocyte typing, cytokine mRNA expression, and crypt cell turnover were compared in ileal pouch biopsy specimens from patients with ulcerative colitis (UC) and familial adenomatous polyposis (FAP). METHODS Biopsy specimens were taken from 17 patients with UC and seven with FAP at a median interval of 19 months (range 2-120) after ileostomy closure. All contained both epithelium and lamina propria. Cryostat sections were stained for lymphocyte subtypes (CD3, CD4, CD8), macrophages (CD68), common leucocyte antigen (CD45), and Ki-67, using a three stage immunoperoxidase reaction. Cytokine mRNA expression for interleukins 2 and 6, tumour necrosis factor alpha, and interferon gamma was studied using an in situ hybridisation technique. RESULTS Lymphocyte subtype and macrophage populations in epithelium and lamina propria were similar in UC and FAP. The labelling index (Ki-67) was significantly increased in biopsy specimens from patients with UC (UC median = 43.3 (interquartile range (IQR) 38.9-48.2) v FAP 34.9 (29.9-35.2), p < 0.05). There was little or no epithelial mRNA expression for any cytokine in any of the specimens. Lamina propria mRNA expression for interleukin 2 was significantly increased in UC (UC median (IQR) 10.7 (5.4-14.2) cells per unit area v FAP 2.8 (1.5-6.6) p < 0.05) but not for tumour necrosis factor alpha, interleukin 6, and interferon gamma. CONCLUSIONS While static morphological assessment (leucocyte type, conventional histopathological examination) was similar, tests of cell function (mRNA expression and labelling index) were different in ileal pouches in patients with UC compared with FAP. The study also showed that mRNA expression occurred almost entirely in the lamina propria.