Association Between Vitamin D Deficiency and Allergic Diseases.

Vitamin D is important for the regulation of bone and muscle metabolism and other functions in the human body. The hydroxylated forms of vitamin D2 and D3 are the most important, however only 1,25(OH)D2 is a fully active product. This hormone exert its pleiotropic actions via the specific receptor VDR, an important transcription factor. The optimal vitamin D concentration in the blood is >20 ng/mL whereas insufficiency and deficiency are 10-20 ng/mL and <10 ng/mL, respectively. To maintain the optimal vitamin D status the total vitamin D intake in children should be at least 400 IU/day. Several studies have shown the effects of vitamin D on proinflammatory cytokines, regulatory T cells and immune response. Vitamin D is a very important activator of the immune response, and in hypovitaminosis D, T killer cells are not able to fight off serious infections. A negative correlation between IgE and vitamin D concentration and a positive relation between vitamin D and lung function was documented in children and teenagers with asthma. In asthmatic children the vitamin D deficiency is associated with a higher corticosteroid use. Vitamin D supplementation in patients with steroid resistant asthma can potentially increase the glucocorticoid therapeutic response. Recently, a new mediator in allergy pathogenesis was reported - IL-33 and its soluble receptor ST2. IL-33 promotes the Th2 lymphocytes response as well as the activation of both mast cells and eosinophils via the ST2 receptor.