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 D(3) [1,25(OH)(2)D(3)], resulting in renal osteodystrophy. However, in recent years, 1,25(OH)(2)D(3) 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)(2)D(3) on the immune system and the implications of vitamin D deficiency, a feature of many patients with CKD, on immune function.