Vitamin D as an immune modulator in multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disorder of the central nervous system. The disease is characterised by inflammation with extensive immune infiltration, demyelination, axonal loss and damage of oligodendrocytes, presumably auto-immune in nature. The influence of environmental factors on the development and activity of MS has been known for a long time. Vitamin D and sun exposure are among the most important ones. Both serum vitamin D level and sun exposure independent of vitamin D production are correlated with epidemiological and clinical parameters of MS, and the impact of vitamin D on immune parameters has been clearly confirmed in experimental studies. Nevertheless, the impact on clinical aspects is inconclusive, especially when the influence of supplementation is assessed. In this work we review the state of knowledge regarding the effect of vitamin D on immune cells subsets in relation to experimental and clinical studies.