ABSTRACT
Vitamin D is classically recognized as a hormone which regulates mineral ion homeostasis in mammalian and avian species. The nutritional importance of vitamin D in the maintenance of normal, human bone metabolism was unfortunately demonstrated with epidemic frequency in the urban centers of industrialized Europe and America in the nineteenth and early twentieth centuries. The utility of simple sunlight exposure in curing rachitic bone disease was first demonstrated by Huldschinsky in 1919, who suggested that environmental sunlight exposure resulted in the endogenous production of a potent “antirachitic substance.” The possibility that 1,25-(OH)2 -D3 may modulate the mammalian immune response was raised by three somewhat divergent lines of evidence.
