Do human γδ T cells respond to M tuberculosis protein antigens?

Diversity of γδ T-cell antigens

In the last two decades, it has become clear that γδ T cells recognize a diverse array of antigens including self and foreign, large and small, and peptidic and non-peptidic molecules. In this respect, γδ antigens as a whole resemble more the antigens recognized by antibodies than those recognized by αβ T cells. Because of this antigenic diversity, no single mechanism-such as the major histocompatibility complex (MHC) restriction of αβ T cells-is likely to provide a basis for all observed T-cell antigen receptor (TCR)-dependent γδ T-cell responses. Furthermore, available evidence suggests that many individual γδ T cells are poly-specific, probably using different modes of ligand recognition in their responses to unrelated antigens. While posing a unique challenge in the maintenance of self-tolerance, this broad reactivity pattern might enable multiple overlapping uses of γδ T-cell populations, and thus generate a more efficient immune response.

Anti-tumour immunotherapy with Vγ9Vδ2 T lymphocytes: from the bench to the bedside

Gamma delta (γδ) Τ cells are non-conventional T lymphocyte effectors that can interact with and eradicate tumour cells. Several data demonstrate that these T cells, which are implicated in the first line of defence against pathogens, have anti-tumour activity against many cancers and suggest that γδ Τ cell-mediated immunotherapy is feasible and might induce objective tumour responses. Due to the importance of γδ Τ lymphocytes in the induction and control of immunity, a complete understanding of their biology is crucial for the development of a potent cancer immunotherapy. This review discusses recent advances in γδ Τ basic research and data from clinical trials on the use of γδ Τ cells in the treatment of different cancers. It analyses how this knowledge might be applied to develop new strategies for the clinical manipulation and the potentiation of γδ Τ lymphocyte activity in cancer immunotherapy.

γδ T cell receptor ligands and modes of antigen recognition

T lymphocytes expressing the γδ-type of T cell receptors (TCRs) for antigens contribute to all aspects of immune responses, including defenses against viruses, bacteria, parasites and tumors, allergy and autoimmunity. Multiple subsets have been individualized in humans as well as in mice and they appear to recognize in a TCR-dependent manner antigens as diverse as small non-peptidic molecules, soluble or membrane-anchored polypeptides and molecules related to MHC antigens on cell surfaces, implying diverse modes of antigen recognition. We review here the γδ TCR ligands which have been identified along the years and their characteristics, with emphasis on a few systems which have been extensively studied such as human γδ T cells responding to phosphoantigens or murine γδ T cells activated by allogeneic MHC antigens. We discuss a speculative model of antigen recognition involving simultaneous TCR recognition of MHC-like and non-MHC ligands which could fit with most available data and shares many similarities with the classical model of MHC-restricted antigen recognition for peptides or lipids by T cells subsets with αβ-type TCRs.