Dendritic cell activation and function in response to Schistosoma mansoni

Dendritic cells (DC) are uniquely specialised for both antigen acquisition and presentation, linking innate and adaptive immunity. Their central role in the activation of naïve T cells gives DC a strategic position in the control of immune responses. While the mechanisms by which viral, bacterial or protozoal pathogens interact with and activate DC are increasingly understood, much less is known about how these cells react to more complex organisms such as schistosomes. Recent studies have examined the impact on DC of antigens from different life cycle stages of Schistosoma mansoni and have revealed a DC phenotype quite distinct to that of conventional activation. Schistosome antigens elicit little of the cytokine secretion and costimulation that are abundantly triggered in DC by unicellular, proinflammatory pathogens and indeed may even actively inhibit such events. The DC response is not a null one, however, since S. mansoni-exposed DC still act as potent antigen presenting cells capable of generating a powerful Th2 immune response. Understanding the interaction between schistosomes and DC is therefore not only addressing fundamental questions of DC biology and immunity to multicellular parasites but also opens the way to therapeutic manipulation of the immune system.