title: Vitamin A status is associated with T-cell responses in Bangladeshi men.
abstract: Recommendations for vitamin A intake are based on maintaining liver stores of > or = 0.070 micromol/g, which is sufficient to maintain normal vision. We propose that higher levels may be required to maintain normal immune function. To test this hypothesis, we conducted an 8-week residential study among thirty-six healthy Bangladeshi men with low vitamin A stores. Subjects were randomised to receive vitamin A (240 mg in four doses) or placebo during study weeks 2 and 3. Vitamin A stores were estimated by isotopic dilution at week 8. Total T-cells, the naive T-cells:memory T-cells ratio and mitogen-induced lymphocyte proliferation were positively and significantly correlated with vitamin A stores (P < 0.05). Mitogen-stimulated IL-2, IL-4 and TNFalpha increased significantly (P < 0.05) in the vitamin A but not placebo group after supplementation, while IL-10 production was significantly and negatively correlated with vitamin A stores (P < 0.05). Segmented linear regression analysis revealed that naive T-cell counts and T-cell blastogenesis were positively associated with vitamin A stores above but not below 0.070 mumol/g liver. These data show that increasing vitamin A stores above the level that maintains normal vision enhances some measures of T-cell-mediated immunity, suggesting a difference in requirements for maintaining vision and immune function.
authors.affiliation: Department of Nutrition, Program in International and Community Nutrition, University of California, Davis, CA, USA.
authors.forename: Shaikh M
authors.initials: SM
authors.lastname: Ahmad
authors.forename: Marjorie J
authors.initials: MJ
authors.lastname: Haskell
authors.forename: Rubhana
authors.initials: R
authors.lastname: Raqib
authors.forename: Charles B
authors.initials: CB
authors.lastname: Stephensen
mesh_terms: D000328:Adult; D049109:Cell Proliferation; D016207:Cytokines / Q000096:biosynthesis; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D007111:Immunity, Cellular; D016130:Immunophenotyping; D018655:Lymphocyte Count; D008297:Male; D010835:Phytohemagglutinins / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D014801:Vitamin A / Q000627:therapeutic use; D014802:Vitamin A Deficiency / Q000188:drug therapy / Q000276:immunology*; D055815:Young Adult
chemical_list: D016207:Cytokines; D010835:Phytohemagglutinins; D014801:Vitamin A