It has been hypothesized that increased expression of the signaling protein p56[sup lck] disrupts maturation of T lymphocytes, leading to the lymphopenia associated with dietary zinc deficiency and malnutrition. Our objective was to examine p56[sup lck] 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[sup +]) T lymphocytes were also investigated after dietary repletion. P56[sup lck] protein levels were one- to two-fold greater in thymocytes than splenocytes, and ZD rats had more thymocyte p56[sup lck] protein than CTL rats. In the thymus and blood, the proportions of T lymphocyte subpopulations (CD4[sup -]CD8[sup -], CD4[sup +]CD8[sup +] and CD4[sup +]CD8[sup -] or CD4[sup -]CD8[sup +]) were unchanged, except for a higher percentage of TCRαβ[sup +]CD4[sup -]CD8[sup +] thymocytes in ZD rats. The 15-29% fewer CD90[sup +] 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[sup lck] protein in ZD rats. In zinc deficiency, the decreased percentages of CD90[sup +] cells in the blood and spleen could adversely affect the T-cell repertoire. [ABSTRACT FROM AUTHOR]
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