The effect of beta-carotene supplementation on the immune function of blood monocytes from healthy male nonsmokers.
Although there is strong epidemiologic evidence that diets rich in carotenoids such as beta-carotene are associated with a reduced incidence of cancer, the cellular mechanisms underlying this phenomenon remain unknown. This article describes the effect of dietary beta-carotene supplementation on both the expression of functionally associated surface molecules on human monocytes and on the secretion of the cytokine tumor necrosis factor-alpha (TNF-alpha) by monocytes, all of which are involved in the initiation and regulation of immune responses involved in tumor surveillance. A double-blind, placebo-controlled, crossover study was undertaken in which 25 healthy, adult male nonsmokers were randomly assigned to receive beta-carotene (15 mg daily) or placebo for 26 days, followed by the alternative treatment for a further 26 days. The expression of functionally related monocyte surface molecules was quantified by flow cytometry, and ex vivo secretion of TNF-alpha was quantified by an enzyme-linked immunosorbent assay, before and after each treatment period. After dietary supplementation there were significant increases in plasma levels of beta-carotene and in the percentages of monocytes expressing the major histocompatibility complex class II molecule HLA-DR and the adhesion molecules intercellular adhesion molecule-1 and leukocyte function-associated antigen-3. In addition, the ex vivo TNF-alpha secretion by blood monocytes was significantly increased after supplementation. These findings suggest that moderate increases in the dietary intake of beta-carotene can enhance cell-mediated immune responses within a relatively short period of time, providing a potential mechanism for the anticarcinogenic properties attributed to beta-carotene.
Hughes
D A
DA
Department of Nutrition, Diet, and Health, Institute of Food Research, Colney, Norwich, UK.
Wright
A J
AJ
Finglas
P M
PM
Peerless
A C
AC
Bailey
A L
AL
Astley
S B
SB
Pinder
A C
AC
Southon
S
S
D000328:Adult; D017951:Antigen Presentation / Q000276:immunology; D000954:Antigens, Surface / Q000096:biosynthesis / Q000187:drug effects / Q000276:immunology; D000975:Antioxidants / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000187:drug effects / Q000276:immunology; D018592:Cross-Over Studies; D004032:Diet; D004311:Double-Blind Method; D005227:Fatty Acids / Q000097:blood; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000187:drug effects / Q000276:immunology; D006801:Humans; D008297:Male; D009000:Monocytes / Q000737:chemistry / Q000187:drug effects*; D010919:Placebos; D012907:Smoking; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019207:beta Carotene / Q000097:blood / Q000276:immunology / Q000494:pharmacology*
D000954:Antigens, Surface; D000975:Antioxidants; D015815:Cell Adhesion Molecules; D005227:Fatty Acids; D000949:Histocompatibility Antigens Class II; D010919:Placebos; D014409:Tumor Necrosis Factor-alpha; D019207:beta Carotene