Natural helper cells: a new player in the innate immune response against helminth infection.

The Th2-type immune response, characterized by the production of IL-4, IL-5, and IL-13, is a critical immune response against helminths invading cutaneous or mucosal sites. Th2 cytokines are induced soon after helminth infection, even before a pathogen-specific adaptive immune response is established. Although the expulsion and clearance of helminths usually requires pathogen-specific Th2-mediated immunity, early induction of Th2 cytokines during the innate immune phase is important for host protection from helminth invasion. Recent studies have shed light on such Th2 cytokine production by formerly uncharacterized innate immune cells such as a newly identified natural helper cell. We discuss here the mechanisms of innate production of Th2 cytokines in host immune responses against helminth infection.