IgG antibodies against common gut bacteria are more diagnostic for Crohn's disease than IgG against mannan or flagellin.

Introduction: Antibodies to baker's yeast (mannan) have been widely used to aid in diagnosis of Crohn's disease. Recently, there has been interest in antibodies against a flagellin from Clostridium coccoides subphylum. We hypothesized that reactivity with these antigens is a surrogate marker for a generalized increased IgG response against intestinal microbiota in Crohn's disease.