Toll-Like Receptor 4-Dependent Activation of Dendritic Cells by β-Defensin 2.

β-Defensins are small antimicrobial peptides of the innate immune system produced in response to microbial infection of mucosal tissue and skin. We demonstrate that murine β-defensin 2 (mDF2β) acts directly on immature dendritic cells as an endogenous ligand for Toll-like receptor 4 (TLR-4), inducing up-regulation of costimulatory molecules and dendritic cell maturation. These events, in turn, trigger robust, type 1 polarized adaptive immune responses in vivo, suggesting that mDF2β may play an important role in immunosurveillance against pathogens and, possibly, self antigens or tumor antigens. [ABSTRACT FROM AUTHOR]