ReviewPlasmacytoid dendritic cells of the gut: Relevance to immunity and pathology

•Plasmacytoid dendritic cells are the principal source of type I interferon.•Plasmacytoid dendritic cells contribute to gastrointestinal homeostasis.•In HIV/AIDS plasmacytoid dendritic cells redistribute to the gut.•Gut-associated plasmacytoid dendritic cells contribute to oral tolerance.

Plasmacytoid dendritic cells (pDCs) are bone marrow-derived immune cells with the ability to express copious amounts of type I and III interferon (IFN) and can differentiate into antigen-presenting dendritic cells as a result of stimulation by pathogen-derived nucleic acid. These powerful combined functionalities allow pDCs to bridge the innate and adaptive immune systems resulting in a concerted pathogen response. The contribution of pDCs to gastrointestinal immunity is only now being elucidated and is proving to be a critical component in systemic immunity. This review will explore the immunology of pDCs and will discuss their involvement in human disease and tolerance with an emphasis on those in the gastrointestinal lymphoid tissue.