Proceedings of the Nutrition Society

A meeting of the Nutrition Society hosted by the Irish Section jointly with the American Society for Nutrition, University College Cork, Republic of Ireland.15–17 June,

70th Anniversary Conference on ‘Vitamins in early development and healthy aging: impact on infectious and chronic disease’

Symposium 3: Vitamin D and immune function: from pregnancy to adolescence

Vitamin D and immune function: an overview

Martin Hewisona1 c1

a1 UCLA and Orthopaedic Hospital Department of Orthopaedic Surgery and the Orthopaedic Hospital Research Center, David Geffen School of Medicine at UCLA, 615 Charles E. Young, Los Angeles, CA 90095, USA

Abstract

Immunomodulatory actions of vitamin D have been recognised for over a quarter of a century, but it is only in the last few years that the significance of this to normal human physiology has become apparent. Two key factors have underpinned this revised perspective. Firstly, there are increasing data linking vitamin insufficiency with prevalent immune disorders. Improved awareness of low circulating levels of precursor 25-hydroxyvitamin D in populations across the globe has prompted epidemiological investigations of health problems associated with vitamin D insufficiency. Prominent among these are autoimmune diseases such as multiple sclerosis, type 1 diabetes and Crohn's disease, but more recent studies indicate that infections such as tuberculosis may also be linked to low 25-hydroxyvitamin D levels. The second factor expanding the link between vitamin D and the immune system is our improved knowledge of the mechanisms that facilitate this association. It is now clear that cells from the immune system contain all the machinery needed to convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D, and for subsequent responses to 1,25-dihydroxyvitamin D. Mechanisms such as this are important for promoting antimicrobial responses to pathogens in macrophages, and for regulating the maturation of antigen-presenting dendritic cells. The latter may be a key pathway by which vitamin D controls T-lymphocyte (T-cell) function. However, T-cells also exhibit direct responses to 1,25-dihydroxyvitamin D, notably the development of suppressor regulatory T-cells. Collectively these observations suggest that vitamin D is a key factor linking innate and adaptive immunity, and both of these functions may be compromised under conditions of vitamin D insufficiency.

(Online publication August 18 2011)

Correspondence

c1 Corresponding author: Professor Martin Hewison, fax +1 310 825 5409, email mhewison@mednet.ucla.edu