Fig. 2
From: What is known about the effects of vitamin D in neuropsychiatric lupus?
Vitamin D metabolism, activation and immunomodulatory effects. Vitamin D3 (cholecalciferol) can be obtained from food intake or by synthesis in the skin of 7-dehydroxycholesterol in response to ultraviolet (UV) light also emitted by sunlight. In the liver, hydroxylation occurs by 25-hydroxylase, forming 25-hydroxyvitamin D3 (25(OH)D3). In the kidneys, 1α-hydroxylase acts in the hydroxylation of 25(OH)D3 to the most biologically active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Both 1,25(OH)2D3 and 25(OH)D3 are immunomodulators by binding to a vitamin D receptor (VDR) present in the nucleus of almost all immune cells. Its immunomodulatory effects include inhibition of monocyte differentiation into dendritic cells, B cell proliferation, plasma cell differentiation and antibody production. The vitamin also induces the activation of natural killer (NK) cells