MUC2 is a mucin glycoprotein secreted by globlet cells. In Science, Cerutti and colleagues show how MUC2 directly promotes tolerance in the small intestine, which has a porous mucous layer. MUC2 is recognized by a receptor complex of galectin 3, the C-type lectin dectin-1 and the inhibitory receptor FcγRIIB on the surface of dendritic cells. Activation of this receptor complex by MUC2 induces the stabilization and nuclear translocation of the transcription factor β-catenin, which interferes with the expression of proinflammatory cytokines. Similarly, activation of dectin-1 and FcγRIIB by MUC2 triggers expression of interleukin 10 and transforming growth factor-β1. Thus, MUC2 contributes to both barrier protection in the large intestine and induction of a tolerizing environment in the small intestine.

Science (26 September 2013) doi:10.1126/science.1237910