Friends in Low Places: Intestinal Commensals Limit Colitis through Molecular Mimicry.

Inflammatory bowel disease is thought to arise from inappropriate inflammation to gut bacteria, yet mechanisms preventing these responses remain elusive. In this issue of Cell, Nanjundappa et al. report that Bacteroides share an epitope with a pancreas-specific peptide that induces protective CD8+ T cells, identifying molecular mimicry as a mechanism to enforce tolerance in the gut.