title: The Active Metabolite of Vitamin D3 as a Potential Immunomodulator.
abstract: In the past, vitamin D was known for its classical, skeletal action as a regulator of calcium and bone homoeostasis. Currently, vitamin D was found to have a role in numerous physiological processes in the human body; thus, vitamin D has pleiotropic activity. The studies carried out in the past two decades showed the role of vitamin D in the regulation of immune system functions. Basically, these effects may be mediated not only via endocrine mechanism of circulating calcitriol but also via paracrine one (based on cell-cell communication that leads to production of signal inducing the changes in nearby/adjacent cells and modulating their differentiation or behaviour) and intracrine mechanism (the action of vitamin D inside a cell) of 1,25-dihydroxycholecalciferol (1,25(OH)2 D3 ) synthetized from its precursor 25-hydroxyvitamin D3 (25(OH)D3 ). Both vitamin D receptor (VDR) and 25-hydroxyvitamin D3 1-α-hydroxylase (CYP27B1) are expressed in several types of immune cells (i.e. antigen presenting cells, T and B cells), and thus, they are able to synthetize the bioactive form of vitamin D that modulates both the innate and adaptive immune system. This review discusses the role of vitamin D as regulator of immune system, and our understanding of how vitamin D regulates both adaptive and innate immunity as well as inflammatory cascade on the cellular level.
authors.affiliation: Department of Immunopathology, Faculty of Medical Science and Postgraduate Training, Medical University of Lodz, Lodz, Poland.
authors.forename: I
authors.initials: I
authors.lastname: Szymczak
authors.affiliation: Department of Immunopathology, Faculty of Medical Science and Postgraduate Training, Medical University of Lodz, Lodz, Poland.
authors.forename: R
authors.initials: R
authors.lastname: Pawliczak
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism; D056704:Adaptive Immunity; D000818:Animals; D017951:Antigen Presentation; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002112:Calcifediol / Q000276:immunology / Q000378:metabolism; D002117:Calcitriol / Q000276:immunology / Q000378:metabolism; D002762:Cholecalciferol / Q000276:immunology* / Q000378:metabolism*; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D007155:Immunologic Factors / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D007155:Immunologic Factors; D002762:Cholecalciferol; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002117:Calcitriol; D002112:Calcifediol; D054804:Cathelicidins