Chronic marginal vitamin A status affects the distribution and function of T cells and natural T cells in aging Lewis rats.
Although both vitamin A (VA) deficiency and aging are independently associated with alterations in immune function, the effects of marginal VA status or VA supplementation on the immune system during aging were not studied. A long-term dietary study was conducted in a rat model of aging to quantify changes in T-cell populations in blood and spleen, including T-cells bearing a marker of natural killer (NKT) cells. The study included nine treatment groups [three levels of dietary VA: marginal (0.35 RE/kg diet), control (4.0 RE/kg diet), and supplemented (50 RE/kg diet); and three age groups: young (2-3 mo), middle-aged (8-10 mo), and old 20-22 mo); diets were fed continuously from weaning to the end of the study period. CD3(+)/CD4(+) T-cells decreased in percentage and number in blood with age, CD8(+) cells increased (%), and the CD4/CD8 ratio decreased. Conversely, aging was associated with increased NKT cells (phenotype CD3(intermediate)/NKR-P1(+)). Based on regression analysis of flow cytometry data, the phenotype of most NKT cells was CD3(intermediate)/NKR-P1(+)/CD28(-). NKT cells, which are most likely of extrathymic origin, accounted for most of the decrease in the CD4/CD8 ratio. Marginal VA status, particularly in older rats, was associated with increases in the percentage of CD8(+) T cells, percentage and number of NKT cells, and peripheral blood cell anti-CD3epsilon-stimulated proliferative response, and decreases in the CD4/CD8 T-cell ratio and splenic cell interleukin-2 production. These differences and the reciprocal changes observed for NKT cells vs. T- and classical NK cells in aging VA-marginal rats suggest that low VA status during aging may increase the risk of infectious or neoplastic diseases that require a normal balance of T-cell or NK-cell responses.
Dawson
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HD
Graduate Program in Nutrition and Department of Nutrition, The Pennsylvania State University, University Park, PA 16802, USA.
Ross
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AC
D000375:Aging / Q000276:immunology* / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002455:Cell Division; D016207:Cytokines / Q000096:biosynthesis / Q000097:blood; D004032:Diet; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology*; D010641:Phenotype; D051381:Rats; D011917:Rats, Inbred Lew; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000502:physiology; D014801:Vitamin A / Q000008:administration & dosage / Q000276:immunology / Q000502:physiology*; D014802:Vitamin A Deficiency / Q000276:immunology
D000911:Antibodies, Monoclonal; D016207:Cytokines; D014801:Vitamin A