1. Pathogenesis of IBD Lloyd Mayer M.D. Mount Sinai Medical Center New York, NY, U.S.A.

2. Model of IBD pathogenesis • Antigen: • Appropriate • Inappropriate Mucosal Inflammation Environment • Modifiers: • Smoking • Appendectomy Genetics

3. NOD2 mutations predispose to the development of Crohn’s disease

5. Immunologic Hypothesis of IBD Inflammatory bowel disease is due to a dysregulated mucosal immune (CD4+ T cell) response to enteric bacterial antigens, in a genetically susceptible host.

6. Summary and conclusions • IBD reflects a combination of environmental, genetic and immunologic defects • The common denominator is an aberrant immune response, either innate or adaptive • Novel cytokines/receptors (e.g. IL23, IL17) play a unique role in disease pathogenesis and may be both distinct and overlapping in CD and UC resulting in the clinical expression of disease