Maturation of dendritic cell 2 phenotype by a helminth glycan uses a Toll-like receptor 4-dependent mechanism

The biology of pathogen-associated molecular patterns (PAMPs) stimulating APCs to differentiate into a Th1-promoting phenotype has been well characterized. Conversely, not a single pathogen product that promotes a Th2 phenotype has been rigorously identified. Strong Th2 responses and dendritic cell 2 maturation are driven by helminth extracts, and carbohydrates have been shown to be responsible for much of this activity. In this study, we show that a helminth carbohydrate, lacto-N-fucopentaose III (LNFPIII) functions as an innate Th2 promoter via its action on murine dendritic cells, with the alpha1-3-linked fucose required for this activity. In contrast to Th1-type PAMPs, which activate extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinases, the Th2 PAMP LNFPIII preferentially activates extracellular signal-regulated kinase. Furthermore, the ability of LNFPIII to drive DC2 maturation is dependent on signaling via Toll-like receptor 4. These data support a new understanding of how APCs integrate signaling pathways to produce a Th1- or Th2-promoting phenotype.