Innate helper cells: a novel cell type essential in the initiation of asthma?

The role of the innate immune system in asthma initiation is being increasingly recognised, and several innate epithelial cytokines, such as interleukin 33 (IL-33), IL-25 and thymic stromal lymphopoietin, have been described as important in asthma pathogenesis. However, until now, the mechanism by which these cytokines initiate Th2 responses and form a link with the adaptive immune system was undetermined. The recent discovery of a new group of non-T, non-B innate helper cells, which are induced by epithelial innate cytokines and secrete the Th2 cytokines IL-4 and IL-13, may provide a mechanism by which the innate and adaptive immune systems become activated in asthma.