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

It has been hypothesized that increased expression of the signaling protein p56lck disrupts maturation of T lymphocytes, leading to the lymphopenia associated with dietary zinc deficiency and malnutrition. Our objective was to examine p56lck protein levels, flow cytometric markers of T cell development (CD4, CD8, TCRαβ, TCRγδ 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. P56lck protein levels were one- to twofold greater in thymocytes than splenocytes, and ZD rats had more thymocyte p56lck 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 TCRαβ+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 p56lck 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.