Delayed Immune Aging in Diet-Restricted B6CBAT6 Fl Mice Is Associated With Preservation of Naive T Cells

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Abstract
Age-related changes in peripheral blood, spleen, and thymus of ad libitum (AL)-fed and dietary restricted (DR) C57BL/6J × CBAJCaH-T6/J Fl (B6CBAT6 Fl) mice at young (3 mo), middle (16 mo), and old (30 mo) ages were studied to define how dietary restriction retards immune aging. Dietary restriction at 25% AL intake level initiated at weaning significantly reduced the rates of age-related declines in peripheral blood T helper cells, naive T helper cells, and naive cytotoxic T lymphocytes (CTLs). As a result, concentrations of these cell types in old DR mice were equivalent to 161%, 176%, and 250% of those in old AL controls. Dietary restriction also abolished age-related splenomegaly and decreased total splenocyte numbers in old DR mice. Dietary restriction did not prevent agerelated decline in thymus size, but preserved thymus cellularity in old mice. Old DR mice had twice as many total thymocytes and 2.6 times as many CD4+CD8+ immature thymocytes as old AL controls. The correlations between total immature thymocytes and concentrations of circulating naive T helper cells and naive CTLs increase with age and become significant in old mice. Thus, dietary restriction preserves immature T-cell precursors in the thymus during aging to maintain higher concentrations of circulating T helper and naive T cells in peripheral blood.

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