Generation of tolerogenic dendritic cells via the E-cadherin/beta-catenin-signaling pathway.

Besides their well-characterized role as the initiator of adaptive immune responses, dendritic cells (DCs) play a critical role in the induction and maintenance of self-tolerance, the failure of which could lead to autoimmune/inflammatory diseases. Although it is clear that tolerance is a property of DCs at the steady state, the molecular mechanisms governing their generation, function and regulation remain elusive. Our recent studies have uncovered the E-cadherin/beta-catenin-signaling pathway as a novel maturation pathway that achieves DC maturation without inflammatory cytokines. As a result, E-cadherin-stimulated DCs elicited an entirely different T cell response in vivo, generating T cells with a regulatory as opposed to an effector phenotype. These DCs induced tolerance in vivo and more importantly, immunization with these DCs provided complete protection against autoimmune diseases in experimental autoimmune encephalomyelitis (EAE). Interestingly, while DCs matured upon disruption of E-cadherin-mediated clusters were functional tolerogenic, upon further TLR ligation, they displayed a strong Th1 cytokine profile and much enhanced antigen presentation capacity consistent with enhanced immunity. Thus, E-cadherin/beta-catenin-signaling might serve as a novel signal that contributes to the elusive steady-state "tolerogenic DCs". Targeting E-cadherin/beta-catenin signaling to either enhance or reduce DC-mediated tolerance might represent an attractive new strategy to achieve antigen-specific immunotherapy for cancers and autoimmune/inflammatory diseases.