Volume 91, Issue 5, May (2004), pp. 741-747 © The Author 2004
doi:10.1079/BJN20041104

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Dietary repletion can replenish reduced T cell subset numbers and lymphoid organ weight in zinc-deficient and energy-restricted rats

Heather J. Hosea¹, Edward S. Rector² and Carla G. Taylor^1
1Departments of Human Nutritional Sciences and
²Immunology, University of Manitoba, Winnipeg, Man. R3T 2N2, Canada

 (Received 15 July 2003–Revised 29 November 2003–Accepted 22 January 2004)

The objective of the present study was to investigate the time course for recovery of lymphoid tissue and T cell subset numbers when Zn-deficient (ZD) or energy-restricted (ER) rats were repleted with control diet; in a second experiment, the link between the stress axis and lymphoid organs was explored. During the deficiency phase, rats were fed a ZD (<1mg Zn/kg) or control diet (30mg Zn/kg, nutritionally complete) either as pair-fed controls (ER) or ad libitum-fed controls (CTL) for 3 weeks. During the repletion phase, all rats were fed control diet ad libitum for 3, 7 or 23d. After the deficiency phase, ZD and ER had lower T cell subset numbers in the thymus compared with CTL, and ZD had reduced T cell subset numbers in the spleen compared with both ER and CTL. T cell subset numbers and lymphoid organ weights recovered from dietary Zn deficiency and energy restriction by 7d of repletion (except 23d for thymus weight in ZD), while body weight required more than 23d for recovery. At the end of the deficiency phase, ZD and ER had higher circulating corticosterone concentrations compared with CTL; plasma TNFα was not detectable and there were no differences in plasma haptoglobin, an acute-phase protein. In conclusion, Zn deficiency and energy restriction elevated circulating corticosterone and reduced T cell subset numbers in the thymus and spleen of growing rats. Repletion with a nutritionally complete diet allowed recovery of T cell subset numbers and lymphoid organ weight.

Keywords:
T cell subsets, Zinc deficiency, Energy restriction, Repletion, Rats

Abbreviations:
ACTH, adrenocorticotropic hormone, CTL, ad libitum-fed control group, ER, energy-restricted group, TCR, T cell receptor, ZD, zinc-deficient group