Innate immune recognition at the epithelial barrier drives adaptive immunity: APCs take the back seat.

Innate immune recognition of microbe-associated molecular patterns by multiple families of pattern-recognition molecules such as Toll-like receptors and Nod-like receptors instructs the innate and adaptive immune system to protect the host from pathogens while also acting to establish a beneficial mutualism with commensal organisms. Although this task has been thought to be performed mainly by specialized antigen-presenting cells such as dendritic cells, recent observations point to the idea that innate immune recognition by stromal cells has important implications for the regulation of mucosal homeostasis as well as for the initiation of innate and adaptive immunity.