Barrier dysfunction and Crohn's disease.

Crohn's disease is a debilitating illness of unknown etiology. A current hypothesis of disease pathogenesis suggests that this illness represents an abnormal immunological reaction to a luminal antigen. As part of this theory it is suggested that the luminal antigen is delivered to the mucosal immune system by a paracellular route. If this theory is correct several testable predictions can be made. In this manuscript these predictions are presented and the evidence to support or refute them is presented.