Balanced approach of gammadelta T cells to type 2 immunity.

Substantial evidence has been accumulated to indicate that gammadelta T cells take part in type 2 immune responses. It is not yet clear, however, in what capacity. Apparently, gammadelta T cells themselves can not only take the function of follicular T helper (T(H)) cells in certain responses, but also can support responses that are dependent on classical help provided by alphabeta T cells. Furthermore, the gammadelta T cells engage as regulators of T(H2) immunity. Here, we consider two mouse models that depend on type 2 immunity, non-specific airway hyperresponsiveness to methacholine after allergen inhalation challenge and the primary IgE response induced by alum-aided immunization, and examine the function of gammadelta T cells. In either case, gammadelta T cells regulate type 2 immunity through balanced enhancing and inhibitory influences. However, after airway allergen exposure, suppressive gammadelta T cells become dominant. The underlying mechanisms are discussed.