Thymic maturation determines gammadelta T cell function, but not their antigen specificities.

gammadelta T cells contribute uniquely to host immune defense, but how they do so remains unclear. Recent work suggests that thymic selection does little to constrain gammadelta T cell antigen specificities, but instead determines their effector fate. When triggered through the T cell receptor, ligand-experienced cells make IFNgamma, whereas ligand-naïve gammadelta T cells produce IL-17, a major initiator of inflammation. These advances warrant a fresh look at how gammadelta T cells may function in the immune system.