Role of gammadelta T lymphocytes in tumor defense.

The effectors of mucosal and natural immunity (i.e. natural killer, NK, cells and NKT lymphocytes) are known to play an important role in host defence against tumors. Gammadelta T lymphocytes are the most represented cell populations in mucosal associated lymphoid tissue and share several characteristics of T and NK cells. Two main subsets of gammadelta T cells are known: one, expressing the Vdelta2 T cell receptor (TCR), is found in the peripheral blood, while T cells expressing Vdelta1 TCR are resident in epithelial tissues. The former subset is capable of killing myeloma and Burkitt lymphoma cells, while the latter has been implied in the defence against epithelial cancers. Furthermore, there is increasing evidence that alphabeta and gammadelta T lymphocytes make distinct contributions to anticancer surveillance. Indeed, unlike alphabeta T cells, gammadelta T lymphocytes are involved in the recognition of antigens that do not undergo the conventional major histocompatibility complex (MHC)-driven antigen presentation. Down-regulation of expression of MHC alleles as well as tumor-specific antigens is observed frequently during tumor progression, resulting in an impairment of MHC-restricted, alphabeta-T-cell-mediated tumor-specific immunity. Given the unique set of antigens recognized and the lack of requirement for classical antigen-presenting molecules, gammadelta T lymphocytes might, therefore, represent a useful and potent system in anti-cancer surveillance, as proposed for the immune response against pathogens. Evidence that gammadelta and alphabeta cells make distinct contribution to anti-cancer surveillance have been recently provided in mice. Here, we discuss the potential role played by resident Vdelta1+ and circulating Vdelta2+ T lymphocytes in the defense against solid tumors and hematological malignancies.