Phenotypic and functional markers for 1α,25‐dihydroxyvitamin D3‐modified regulatory dendritic cells

The clinical use of dendritic cells (DCs) to induce antigen‐specific immune tolerance has been hampered by the lack of a widely acknowledged method for generating human regulatory DCs but even more so by the non‐existence of reliable markers. Thus, we set out to find reliable markers that can be measured with simple methods to identify regulatory DCs that are applicable for future clinical studies. Human DCs were generated from peripheral blood monocytes in the presence of 1α,25‐dihydroxyvitamin D₃ (VD3), which gave rise to a phenotype that resembles immature DCs, with the exception of high CD14 and reduced CD1a on the cell surface. These VD3‐treated DCs exert a long‐lasting inefficient T cell stimulation and induce T cell hyporesponsiveness with regulatory potential. Importantly, such VD3‐treated DCs were readily distinguishable from untreated DCs by low levels of interleukin‐23 secretion and low expression of miR‐155 upon exposure to maturation stimuli. Furthermore, VD3‐treated DCs showed over‐expression of miR‐378. All these features can be used as robust markers for quality control of VD3‐treated regulatory DCs in future clinical studies.