Vitamin C promotes the proliferation and effector functions of human γδ T cells

γδT cells are of interest as effector cells for cellular immunotherapy due to their HLA-non-restricted lysis of many different tumor cell types.Potential applications include the adoptive transfer of in vitro-expandedγδT cells.Therefore,it is important to optimize the culture conditions to enable maximal proliferative and functional activity.Vitamin C(L-ascorbic acid)is an essential vitamin with multiple effects on immune cells.It is a cofactor for several enzymes,has antioxidant activity,and is an epigenetic modifier.Here,we investigated the effects of vitamin C(VC)and its more stable derivative,L-ascorbic acid 2-phosphate(pVC),on the proliferation and effector function of humanγδT cells stimulated with zoledronate(ZOL)or synthetic phosphoantigens(pAgs).VC and pVC did not increaseγδT-cell expansion within ZOL-or pAg-stimulated PBMCs,but increased the proliferation of purifiedγδT cells and 14-day-expandedγδT-cell lines in response toγδT-cell-specific pAgs.VC reduced the apoptosis ofγδT cells during primary stimulation.While pVC did not prevent activation-induced death of pAg-restimulatedγδT cells,it enhanced the cell cycle progression and cellular expansion.Furthermore,VC and pVC enhanced cytokine production during primary activation,as well as upon pAg restimulation of 14-day-expandedγδT cells.VC and pVC also increased the oxidative respiration and glycolysis ofγδT cells,but stimulus-dependent differences were observed.The modulatory activity of VC and pVC might help to increase the efficacy ofγδT-cell expansion for adoptive immunotherapy.