LEUKOCYTE TYPING, CYTOKINE EXPRESSION, AND EPITHELIAL TURNOVER IN THEILEAL POUCH IN PATIENTS WITH ULCERATIVE-COLITIS AND FAMILIAL ADENOMATOUS POLYPOSIS

Background/Aims-Conventional histopathology, leucocyte typing, cytokin e mRNA expression, and crypt cell turnover were compared in heal pouch biopsy specimens from patients with ulcerative colitis (UC) and famil ial adenomatous polyposis (FAP). Methods-Biopsy specimens were taken f rom 17 patients with UC and seven with FAP at a median interval of 19 months (range 2-120) after ileostomy closure. All contained both epith elium and lamina propria. Cryostat sections were stained for lymphocyt e subtypes (CD3, CD4, CD8), macrophages (CD68), common leucocyte antig en (CD45), and Ki-67, using a three stage immunoperoxidase reaction. C ytokine mRNA expression for interleukins 2 and 6, tumour necrosis fact or alpha, and interferon gamma was studied using an in situ hybridisat ion technique. Results-Lymphocyte subtype and macrophage populations i n epithelium and lamina propria were similar in UC and FAP. The labell ing 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 m RNA expression for any cytokine in any of the specimens. Lamina propri a 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, an d interferon gamma. Conclusions-While static morphological assessment (leucocyte type, conventional histopathological examination) was simil ar, tests of cell function (mRNA expression and labelling index) were different in heal pouches in patients with UC compared with FAP. The s tudy also showed that mRNA expression occurred almost entirely in the lamina propria.