Dietary zinc deficiency lowers the proportions of splenic CD90+ (Thy-1+) B-cells and late thymic emigrant T-cells in growing rats.

Zn-deficient (ZD) rats have a lower proportion of splenic CD90 + T-cells which could be due to fewer new T-cells exiting the thymus, defective post-thymic maturation or increased cell death. Post-thymic maturation of splenic lymphocytes and their viability were determined by flow cytometry in weanling rats assigned to ZD (< 1 mg Zn/kg; ad libitum), diet-restricted (DR; 30 mg Zn/kg; limited to the amount of feed as consumed by ZD rats), marginally Zn-deficient (MZD; 10 mg Zn/kg; ad libitum) or control (30 mg Zn/kg; ad libitum) groups for 3 weeks. ZD rats had a 29 % lower percentage of splenic CD90 + T-cells and both ZD and DR rats had a 30 % lower proportion of splenic CD90 + B-cells compared with control rats. When the splenic CD90 + T-cells were characterised further, there was no difference among the groups in the first two stages of post-thymic development; however, ZD, DR and MZD rats had a 42% lower proportion of late thymic emigrants (TCRαβ + CD90 + CD45RC+RT6.1 + ) compared with control rats. There was no difference among groups in the proportion of splenic CD90 + T-cells in the non-viable region; however, ZD rats had a higher proportion of CD90 + B-cells in the non-viable region compared with MZD and control animals, suggesting that this phenotype was more susceptible to cell death during deficiency. The lower proportion of splenic CD90 + T-cells in ZD rats does not appear to be due to a defect in thymic production or increased cell death in the spleen. Future studies should determine if late thymic emigrants have homed to other peripheral organs.