Antiflagellin antibodies suggest infective participation in irritable bowel syndrome pathogenesis

Irritable bowel syndrome (IBS) is a functional disorder of multifactorial origin. Recent attention has been paid to the potential role of immune activation in intestinal sensorimotor dysfunction and symptom generation in patients with IBS. The link between immune activation and IBS is further supported by the evidence that IBS may develop after an acute episode of infectious gastroenteritis, IBS-like symptoms may precede the diagnosis or accompany a period of remission of inflammatory bowel disease (IBD), and quantitative histopathologic data demonstrate the presence of low-grade mucosal immune infiltration in a large subset of patients with IBS. These data also suggest some areas of potential overlap between IBS and IBD. The present study explored the possibility that, similarly to IBD patients, IBS patients have antibodies directed against certain components of indigenous flora, such as flagellin (the primary structural component of bacterial flagella). The authors demonstrated that, compared with healthy controls, antibodies against flagellin were recognized more frequently in patients with IBS. Furthermore, these antibodies were found more frequently in postinfectious compared with unspecific IBS. In patients with Crohn's disease, antiflagellin antibodies were detected with an increased frequency and at higher concentrations than in patients with IBS. All together, these results indicated the presence of a systemic immune activation in IBS patients, characterized by specific antibodies directed against luminal bacterial antigens. Furthermore, these results support the hypothesis that a subset of IBS presents an immune activation with pathogenic features common with IBD.