The mechanisms of tissue damage in ulcerative colitis and Crohn's disease may reflect disordered humoral or cell-mediated effector mechanisms, respectively. Mucosal biopsies from untreated inflammatory bowel disease patients and normal controls were analysed for the expression of granzyme B, a cytotoxic effector molecule specifically associated with cell-mediated immunity, and for regulatory cytokines. Messenger RNA (mRNA) was analysed by reverse transcription-polymerase chain reaction and enzyme-linked oligonucleotide chemiluminescence assay. Mucosal biopsies were analysed by immunohistochemistry for granzyme B protein and lymphocyte markers and for the presence of apoptotic cells by terminal deoxynucleotidyl transferase end labelling. Granzyme B mRNA was elevated in Crohn's disease, but not in ulcerative colitis or control mucosal biopsies. Granzyme B mRNA levels correlated with interferon gamma mRNA levels in Crohn's disease. Granzyme B was expressed in CD3+, CD8+ T cells in the lamina propria of Crohn's disease mucosa and there were significantly more apoptotic cells in the lamina propria in Crohn's disease. In conclusion, granzyme B-expressing T lymphocytes are present in the focal mucosal lesions of Crohn's disease, together with spatially related apoptotic cell death. These results support the hypothesis that T-cell-mediated cytotoxic effector mechanisms may play a role in Crohn's disease.
Copyright 2000 John Wiley & Sons, Ltd.