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Nutritional Immunology
Research Communication

Zinc-Deficient Rats Have Fewer Recent Thymic Emigrant (CD90+) T Lymphocytes in Spleen and Blood¹

Departments of Human Nutritional Sciences and ^* Immunology, University of Manitoba, Winnipeg, MB, Canada R3T 2N2

²To whom correspondence should be addressed. E-mail: ctaylor{at}ms.umanitoba.ca.

It has been hypothesized that increased expression of the signaling protein p56^lck disrupts maturation of T lymphocytes, leading to the lymphopenia associated with dietary zinc deficiency and malnutrition. Our objective was to examine p56^lck protein levels, flow cytometric markers of T cell development (CD4, CD8, TCRß, TCR and CD90) and absolute cell numbers in thymus, spleen and blood of zinc-deficient (ZD), diet-restricted (DR) and control (CTL) rats. Recent thymic emigrant (CD90⁺) T lymphocytes were also investigated after dietary repletion. P56^lck protein levels were one- to twofold greater in thymocytes than splenocytes, and ZD rats had more thymocyte p56^lck protein than CTL rats. In the thymus and blood, the proportions of T lymphocyte subpopulations (CD4^-CD8^-, CD4⁺CD8⁺ and CD4⁺CD8^- or CD4^-CD8⁺) were unchanged, except for a higher percentage of TCRß⁺CD4^-CD8⁺ thymocytes in ZD rats. The 15–29% fewer CD90⁺ T cells in the blood and spleen of ZD rats were reversed after dietary repletion for 7 and 23 d, respectively. In summary, T-cell numbers were proportional to thymus and spleen weights and unaltered per unit blood volume, despite elevated thymocyte p56^lck protein in ZD rats. In zinc deficiency, the decreased percentages of CD90⁺ cells in the blood and spleen could adversely affect the T-cell repertoire.

KEY WORDS: • zinc • T lymphocytes • p56^lck • recent thymic emigrants • rats