Vitamin D3 inhibits the proliferation of T helper cells, downregulate CD4 + T cell cytokines and upregulate inhibitory markers.

1 α, 25-dihydroxyvitamin D3 (VitD3) has been suggested to have strong modulatory properties in the immune system. Researchers in the present study primarily aimed to understand the effect of VitD3 on human CD4+ T cell proliferation in antigen presenting cells (APCs) free condition in vitro. The effect of VitD3 on intracellular cytokine responses trend to Th1, Th2, Th17 and Th22 was evaluated using the flow cytometry. Moreover the effect of VitD3 on the expression of inhibitory markers such as PD1, PD-L1, and CTLA4 which are induced upon polyclonal T cell receptor (TCR) activation on CD4+ T cells, was assessed. We observed that the stimulation of CD4+ T cells with VitD3, suppressed proliferation capacity, enhanced the expression of PD1, PD-L1 and CTLA4 inhibitory markers on CD4+ T cells, and diminished the percentage of pro-inflammatory cytokines including, IFN-γ, IL-17, and IL-22 except IL-4 in CD4+ T cells. The data suggested a potential insight into the consideration of VitD3 in the prevention/control of pro-inflammatory immune response/autoimmune disorders.