Inducible and constitutive β-defensins are differentially expressed in Crohn's disease and ulcerative colitis

Antimicrobial peptides such as defensins provide nonspecific mucosal defense against a multitude of microorganisms. Recently, it has been shown that luminal bacteria may invade the mucosa in inflammatory bowel diseases, suggesting a defect in innate mucosal immunity. The aim of this study was to investigate the expression of human beta-defensins (HBD) in controls. Crohn's disease (CD), ulcerative colitis (UC), and unspecific inflammation. Up to 4 biopsies were taken from 103 patients (33 controls, 24 with Crohn's disease, 36 with ulcerative colitis, 10 with unspecific colitis). Mucosal mRNA was measured using real-time fluorescence temperature cycler reverse-tran script ion polymerase chain reaction with primers for HBD-1, HBD-2. HBD-3. tumor necrosis factor a, and interleukin 8. Mucosal HBD-1 expression was marginally decreased in both CD and UC. HBD-2 was increased exclusively in UC but not in CD. The expression of the novel defensin HBD-3 was strongly correlated with HBD-2 and also raised predominantly in UC. The expression of both inducible beta-defensins was enhanced in the state of inflammation. Expression of HBD-2 showed a weak correlation with interleukin 8 only in inflamed CD biopsies but not with tumor necrosis factor a. The missing induction of both inducible beta-defensins in CD as compared with UC may cause a defect in barrier function that predisposes to bacterial invasion.