title: Effect of beta-carotene on lymphocyte subpopulations in elderly humans: evidence for a dose-response relationship.
abstract: The effects of various doses (0, 15, 30, 45, and 60 mg/d) of supplementary beta-carotene were evaluated. The percentage of lymphoid cells with surface markers for T-helper and natural killer (NK) cells and cells with interleukin 2 (IL-2) and transferrin receptors were significantly and substantially increased in peripheral blood mononuclear cells collected from older human adult volunteers after supplementation with greater than or equal to 30 mg beta-carotene/d for 2 mo. The increase in the percentage of cells with markers of NK cells and in expression of IL-2 receptors was dose dependent. The plasma concentrations of beta-carotene were also elevated significantly; however, there was no increase in the amount of retinol present in plasma. This indicated that immunomodulation induced by beta-carotene may be due to the carotenoid rather than to an increased amount, and hence actions, of vitamin A. These results support the role of immunostimulation as a potential mechanism of action of beta-carotene with cancer-prevention potential.
authors.affiliation: Department of Family and Community Medicine, College of Medicine, University of Arizona, Tucson 85724.
authors.forename: R R
authors.initials: RR
authors.lastname: Watson
authors.forename: R H
authors.initials: RH
authors.lastname: Prabhala
authors.forename: P M
authors.initials: PM
authors.lastname: Plezia
authors.forename: D S
authors.initials: DS
authors.lastname: Alberts
mesh_terms: D000368:Aged; D000375:Aging / Q000276:immunology* / Q000378:metabolism; D002338:Carotenoids / Q000008:administration & dosage* / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007694:Killer Cells, Natural / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D015375:Receptors, Interleukin-2 / Q000097:blood; D011990:Receptors, Transferrin / Q000097:blood; D016176:T-Lymphocyte Subsets / Q000378:metabolism*; D006377:T-Lymphocytes, Helper-Inducer / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000378:metabolism; D014801:Vitamin A / Q000097:blood; D019207:beta Carotene
chemical_list: D015375:Receptors, Interleukin-2; D011990:Receptors, Transferrin; D019207:beta Carotene; D014801:Vitamin A; D002338:Carotenoids