γδ cells and tumor microenvironment: A helpful or a dangerous liason?

gamma delta T cells are a subset of T lymphocytes that have been implicated in immunosurveillance against infections and tumors. T cells are endowed with antitumor activities, and hence several T cell-based small-scale clinical trials have been conducted either by in vivo activation by intravenous administration of aminobiphosphonates or by adoptive transfer of invitro expanded T cells. Although both these strategies have yielded promising results, there are a number of limitations associated with each of them which, if overcome may help to further improve efficacy. One of the most important limits is the possible polarization of tumor-infiltrating T cells toward different T cells population with functional activities that help the progression and spread of the tumor. Here, we review the modalities and the possible mechanisms involved in the polarization of tumor-infiltrating T cells upon interaction with several components of the tumor microenvironment and discuss their implications for the manipulation of T cells in cancer immunotherapy.