Tuberculosis & D
Over 100 years ago doctors observed that moving patients to sunny environments ameliorated their symptoms of tuberculosis (TB), although the reason was not understood. Today, scientific studies are beginning to identify vitamin D, generated by the skin's exposure to sunlight, as one of the keys to activating the body's immune response to the bacteria that causes TB.
Scientists have been studying the biological mechanism by which vitamin D enhances the immune response, not just to protect us from TB but other bacterial infections and autoimmune diseases.
Other citations on the subject:
http://www.ncbi.nlm.nih.gov/pubmed/20156523
http://www.ncbi.nlm.nih.gov/pubmed/21995874
http://www.ncbi.nlm.nih.gov/pubmed/21419266