Figure 2

PSA mediated protection from inflammatory disease in experimental models of colitis. Transfer of CD4⁺CD45Rb^high T cells into Rag^−/− mice colonized with Helicobacter hepaticus induces colitis. Rag^−/− mice co-colonized with H. hepaticus and B. fragilis expressing PSA, but not B. fragilis lacking PSA expression, do not develop colitis. PSA mediated protection against colitis results from decreased levels of cytokines associated with the Th17 lineage including IL-1beta, IL-23, and TNF-alpha. Suppression of the inflammatory cytokines is dependent on IL-10. In the absence of IL-10, PSA cannot prevent colitis in co-colonized mice.