Accumulating evidence suggests that γδ T cells play roles in host immune responses to inflammations/damages, tumors and infections. Recent studies have demonstrated that roles of γδ T cells can be quite broad or diverse. In this special issue, seven review articles discuss recent progress conceiving the diverse immunologic roles in γδ T cells.

Born et al.1 summarize experimental findings implicating that γδ T cells recognize a diverse array of antigens including self and foreign, large and small, and peptidic and non-peptidic molecules. In parallel, Kalyan and Kabelitz2 discuss unique and empathetic aspects of γδ T cells in terms of antigen recognition, immune response and effector function. Caccamo et al.3 present recent observations suggesting that human γδ T cells can evolve into multiple T helper-like effector functions, with plasticity feature. While Fournié et al.4 identify recently gained information regarding human γδ T cell-targeted clinical trials for immunotherapy against late-stage cancers, Li et al.5 summarize results in studies of γδ T cells in HIV-infected humans. Tu's group6 outlines anti-infection potential of γδ T cells. Finally, Chen7 reviews recent publications suggesting multifunctional immune responses and effector functions of phosphoantigen-specific γδ T cells in tuberculosis and other infections in humans and nonhuman primates.

These reviews are comprehensive and up-to-date, supporting the view that γδ T cells play broad immunological roles in host responses. The in-depth discussions also provide provocative speculations and hypotheses that will facilitate future studies of γδ T cells.