Table 2.

Studies in animal models and in humans on the effects of vitamin D in RA

Studies in animal models	Studies in humans
↓ development and severity (e.g., hind paw swelling, bone erosion) [103, 104] ↓ autoantibodies production [102] ↓ Th1, Th17, ↑ Treg cells, ↓ IL-17, IFN-γ [105]	In vitro studies: ↓ TNF-α, IL-1α, IL-1β, IL-6 ↓ RANKL [106] ↑ tolerogenic DCs [107] Clinical studies: ↓ disease risk [114] ↓ disease activity [113, 115, 116] no improvement in RA outcomes [117]

RANKL Receptor activator of nuclear factor κβ ligand, DCs Dendritic cells. ↓ indicates decrease, ↑ indicates increase