Vitamin D insufficiency: implications for the immune system

Chronic kidney disease (CKD) is characterized by a loss of kidney function and dysregulation of vitamin D metabolism. Well known are the defects in final activation of vitamin D to 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], resulting in renal osteodystrophy. However, in recent years, 1,25(OH)₂D₃ has been identified as having effects far beyond calcium and bone metabolism. In this review, specific attention is given to the effects of 1,25(OH)₂D₃ on the immune system and the implications of vitamin D deficiency, a feature of many patients with CKD, on immune function.