Osteoimmunology: calcium, bone, vitamin D, and allergy
1Policlinico Gemelli, Rome, Italy.
Vitamin D (Vit D) is a fat-soluble, steroid hormone, and can be acquired either through the skin after exposure to sunlight and/or through feeding. The term Vit D includes both vitamins D2 and D3. Vit D is known to participate in bone metabolism, calcium and immune diseases, including allergies. The immune action of this vitamin is carried out at the level of both innate and adaptive immunity. In fact, Vit D receptors are expressed on primary immune cells, such as monocytes and dendritic cells, but also on secondary cells such as T and B lymphocytes. Vit D deficiency is often also considered as a risk factor for food allergies. Radiation on the skin reduces the production of Vit D and increases the risk of allergies. Therefore, good levels of Vit D and/or higher serum levels protect from respiratory infections and allergies. In addition, Vit D therapy seems to reduce the risk of influenza viral infections and the related inflammatory response.