The effects of dietary zinc supplement on intracellular zinc concentration in bovine immune cells

Abstract Zinc (Zn) is one of the most abundant metals in our body and is critical for innate and adaptive immune functions. In humans and mice, Zn deficiency may lead to immunodeficiency, reduced reproductive health, and increased disease susceptibility. However, trace mineral requirements and evidence of Zn dysregulation are poorly defined in cattle. This study aimed to evaluate intracellular Zn concentrations in immune cells from young growing steers with different Zn dietary supplements. Eighteen Angus crossbred steers were stratified by body weight and randomly assigned to two dietary treatments groups: 1) control, no supplemental Zn, or 2) high Zn; 150 ppm of Zn delivered in premixes in total mixed rations. To evaluate the intracellular Zn concentration of immune cells, whole blood cells were loaded with FluoZinTM-3, a fluorescent cell-permeant Zn indicator, then stimulated with Zn pyrithione (100 μM) or TPEN [N,N,N′,N′-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine] (50 μM) to measure maximum and minimum mean fluorescent intensity. Cells were stained with surface antibodies to identify immune cell populations and data were collected by flow cytometry. The intracellular Zn concentrations of circulating CD8 T cells and γδ T cells, but not other populations, differed significantly between treatment groups. These results indicate that intracellular Zn concentration can be influenced by dietary Zn intake, and that certain immune populations are differentially affected by Zn status. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2020-06540 from the USDA National Institute of Food and Agriculture.