title: Effects of ultraviolet light on human serum 25-hydroxyvitamin D and systemic immune function.
abstract: BACKGROUND
  Many immune-mediated diseases are associated with low levels of vitamin D and sunlight. UV light or supplementation with vitamin D can increase regulatory T-cell activity and prevent animal models of autoimmune disease. Increasing population vitamin D levels may therefore alleviate the burden of human immune-mediated disease.
  
  
  OBJECTIVE
  To determine the responses of circulating 25-hydroxyvitamin D [25(OH)D] levels, regulatory T-cell numbers, and immune function to UV light exposure in patients being treated for skin disease.
  
  
  METHODS
  Twenty-four subjects with skin disease from the North of Scotland were recruited between December and March. At baseline, and after 2 and 4 weeks of narrowband UV light exposure, we measured peripheral blood 25(OH)D level, numbers of regulatory T cells (CD4(+)CD25(hi)FoxP3(+)), and T-cell proliferative and cytokine responses to anti-CD3/CD28 stimulation.
  
  
  RESULTS
  Median (interquartile range) narrowband UV-B received during the study was 39.1 (30.9) as standard erythema dose, comparable to a quarter of the median summer sunlight exposure received locally. This increased the 25(OH)D level from a mean ± SD of 34 ± 17 nmol/L to 58 ± 16 nmol/L after 2 weeks and 78 ± 19 nmol/L after 4 weeks. The mean proportion of circulating regulatory T cells increased from 0.5% to 1.6% CD3(+) cells, which significantly correlated with the increased 25(OH)D level. UV treatment was also followed by reduced proliferative and IL-10 responses to anti-CD3/CD28 independent of the 25(OH)D level.
  
  
  CONCLUSIONS
  Narrowband UV light reduces systemic immune responsiveness via the induction of regulatory T cells. Light and 25(OH)D levels may affect particular immune functions independently. The levels of serum 25(OH)D over which these effects are apparent should guide future interventions.
authors.affiliation: Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Sarah V I
authors.initials: SV
authors.lastname: Milliken
authors.forename: Heather
authors.initials: H
authors.lastname: Wassall
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Lewis
authors.forename: Judith
authors.initials: J
authors.lastname: Logie
authors.forename: Robert N
authors.initials: RN
authors.lastname: Barker
authors.forename: Helen
authors.initials: H
authors.lastname: Macdonald
authors.forename: Mark A
authors.initials: MA
authors.lastname: Vickers
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Ormerod
mesh_terms: D000328:Adult; D000368:Aged; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D006801:Humans; D007109:Immunity / Q000528:radiation effects*; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013472:Sunlight; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000528:radiation effects; D055815:Young Adult
chemical_list: D016207:Cytokines; D014807:Vitamin D; C104450:25-hydroxyvitamin D