The above therapeutic mechanism of the UVB radiation is highlighted via the elevated serum levels of 25(OH) Vitamin D (the serum marker of vitamin D) in PsO patients undergoing UVB phototherapy [55]; Vitamin D binds to the Vitamin D receptor (VDR) exhibiting an immunomodulatory activity by decreasing IL-17 and IFNγ levels on Peripheral Blood Mononuclear Cells (PBMCs) [56], while Vitamin D deficiency displays a perturbated differentiation and increased proliferation of KCs [57]. The gene discussed is VDR; the disease is vitamin D deficiency.