Triple costimulation via CD80, 4-1BB, and CD83 ligand elicits the long-term growth of Vγ9Vδ2 T cells in low levels of IL-2.

Human gd T cells play important roles in the regulation of infection and cancer. To understand the roles of costimulatory signals in activation and expansion ex vivo, Vg9Vd2 T cells were grown with artificial APCs that express CD83, 4-1BB ligand, and/or CD32, which allowed a loading of aCD3 and aCD28 antibodies. The costimulatory signals through CD80, 4-1BB, and CD83 ligand in low levels of IL-2 triggered an explosive ex vivo proliferation of Vg9Vd2 T cells capable of secreting high levels of IL-2, IFN-g, and TNF-a. Moreover, the triplecostimulatory signals cause augmented cell viabilities for long-term growth of Vg9Vd2 T cells, resulting in phenotypic changes to CD27 2 CD45RA + effector memory-like cells. Notably, we observed that CD83 ligand signaling is crucial to promote ex vivo expansion, survival, and cytolytic effector functions of Vg9Vd2 T cells. In contrast, 4-1BB signaling is moderately important in up-regulating surface molecules on Vg9Vd2 T cells. Consequently, gd T cells stimulated in the presence of triple-costimulatory signals have diverse cytolytic effector molecules, including perforin, granzyme A, granzyme B, and Fas ligand, eliciting potent cytolytic activities against tumor cells. Overall, our results provide insights into the roles of costimulatory signals in manufacturing long-lived and fully functional Vg9Vd2 T cells that could be useful against cancers. J. Leukoc. Biol. 99: 000–000; 2016.