Do bacterial antigens worsen the symptoms of CD?

"Bacterial flagellin is a dominant antigen in Crohn disease" in J Clin Invest (2004)"... we favor the hypothesis that the B and T cell responses to flagellin contribute more directly to the chronic intestinal inflammation seen in IBD.
... Our clinical data (Figure 6) are consistent with the fact that the aberrant response in patients with CD is specific to the subgroup of flagellins identified in our molecular screen. ... The question of the basis for selective responses to an antigen present in the normal commensal flora of most (if not all) individuals is a challenging one. ... ). Alternatively, alterations in barrier function (30, 31) or intrinsic innate immune responses (32, 33) may enhance the likelihood of the response to these flagellin molecules in patients prone to develop IBD.
... In general, the data are consistent with the hypothesis that IBD is associated with a defect in tolerance to commensal organisms. The IgG2a-biased antibody against Fla-X and CBir1 highlights the Th1 bias of the T cell responses seen. The broad recognition of these flagellins in several different mouse models and in humans with CD indicates that these flagellins are among the immunodominant antigens of the microbiota. However, the exact role of these flagellins in the pathogenesis of IBD (e.g., whether they are predominant or obligatory for disease) compared with that of other microbial antigens remains to be defined. We favor a model in which a T regulatory response to specific flagellins (and/or other bacterial antigens) may be selectively impaired in IBD. In this context, specific flagellin molecules may represent novel targets for antigen-directed therapy in IBD. Experiments are currently underway to address this possibility. ... Given the heterogenous nature of IBD and the complexity of the intestinal microflora, we are continuing our efforts to identify additional antigens in patients that do not respond to flagellin. It will be of considerable interest to determine how the reactivity against these antigens correlates with genetic determinants, clinical phenotypes, and responses to treatment."