1,25-Dihydroxyvitamin D₃ impairs the differentiation of effector memory T cells in vitro in multiple sclerosis patients and healthy controls

Vitamin D deficiency is associated with increased susceptibility to multiple sclerosis (MS) and increased disease activity. Vitamin D is a potent immunomodulator but the effects of vitamin D treatment on T cell memory have not been explored. We studied the effects of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) on T cell memory in MS patients (n=10) and healthy controls (n=10). In vitro treatment of PBMC cultures with 1,25(OH)₂D₃, led to a decrease in the proportion of effector memory T cells with an increase in naïve T cells, compared to vehicle in both groups. Further studies to unravel the mechanism of this effect and to understand its long-term implications are required.