Interactions between the host innate immune system and microbes in inflammatory bowel disease

Diagnostic value, clinical utility and pathogenic significance of reactivity to the molecular targets of Crohn's disease specific-pancreatic autoantibodies

Pancreatic autoantibodies (PAB) giving characteristic staining patterns of the exocrine pancreas by indirect immunoflourescence appear to be specific markers of Crohn's disease (CrD), being present in approximately 30% of patients with CrD and in less than 5% of patients with ulcerative colitis (UC). Some studies have suggested that PAB are associated with specific disease phenotypes and that their detection may be of clinical significance. Thorough investigation of the role of PAB in the immunopathogenesis of inflammatory bowel diseases (IBD) has been hampered due to the lack of identity of their antigenic targets. The recent identification of the pancreatic zymogen granule protein 2 (GP2) as the major target of PAB has led to the development of an enzyme immunoassay that helps determine the diagnostic and clinical relevance of antigen-specific immune responses. Recent studies have demonstrated that GP2 is expressed on the apical surface of intestinal membranous cells of the follicle-associated epithelium, and is essential for host-microbial interaction and the initiation of bacteria-specific mucosal immune responses. This review critically discusses recent reports investigating the diagnostic and clinical utility of GP2-specific autoantibody responses in patients with IBD. Hints towards a better understanding of the immunogenicity of GP2 are also provided.

The intestinal microbiota and chronic disorders of the gut

Mucosal surfaces of the gut are colonized by large numbers of heterogeneous bacteria that contribute to intestinal health and disease. In genetically susceptible individuals, a 'pathogenic community' may arise, whereby abnormal gut flora contributes to alterations in the mucosa and local immune system leading to gastrointestinal disease. These diseases include enteric infections, such as Clostridium difficile infection, small intestinal bacterial overgrowth, functional gastrointestinal disorders (including IBS), IBD and colorectal cancer. Prebiotics, probiotics and synbiotics (a combination of prebiotics and probiotics) have the capacity to reverse pathologic changes in gut flora and local immunity. Intestinal health and disease need to be thoroughly characterized to understand the interplay between the indigenous microbiota, the immune system and genetic host factors. This Review provides a broad overview of the importance of the intestinal microbiota in chronic disorders of the gut.