The present experiment aimed at understanding the effects of cortisol levels on sheep peripheral blood mononuclear cell (PBMC) proliferation and cytokine production during hyperthermia. To mimic stress related to the exposition of high ambient temperatures, PBMC were cultured at 43°C for 12 h, and subsequently at 39°C for additional 12 h. Cells in normothermia were cultured at 39°C for 24 h. Phytohemagglutinin-stimulated PBMC were cultured with different cortisol levels: 0 ng/mL; 100 ng/mL, representing the physiological cortisol concentration simulating stress condition (Cort100); and 1,000 ng/mL, representing the hyperactivated hypothalamic-pituitary-adrenal axis (Cort1000). Phytohemagglutinin-stimulated PBMC with 0 ng/mL of cortisol concentration represented the positive control, whereas nonstimulated PBMC without cortisol represented the negative control (NC). The free cell supernatants were collected for the determination of IL-6, IL-1β, and IL-10 by ELISA. Bromodeoxyuridine assay was performed on cells to determine cell proliferation. Exposition to hyperthermia negatively affected cell proliferation, IL-6, IL-1β, and IL-10 concentrations in cell supernatants. The interaction of hyperthermia and cortisol level affected both cell proliferation and IL-10 production. Both PBMC proliferation and IL-10 production in positive control, Cort100, and Cort100 decreased at 43°C as compared with 39°C NC. On average, the Cort100 treatment displayed higher concentrations of IL-6 than NC. The present experiment demonstrated that the action of cortisol concentration simulating stress condition on cell proliferation and cytokine production was a permissive/stimulatory action during normothermia, whereas it was a suppressive action during hyperthermia. These data confirmed that cortisol concentration simulating stress condition could have a role in the immune system of sheep via mediating cellular homeostasis in the condition of hyperthermia. The negative effects of hyperthermia on sheep immune responses were apparent when performing an immunological challenge.

本实验旨在了解皮质醇水平对热疗期间绵羊外周血单核细胞（PBMC）增殖和细胞因子产生的影响。为了模拟与暴露于高环境温度有关的压力，PBMC在43°C下培养12小时，然后在39°C下再培养12小时。在常温下的细胞在39°C下培养24小时。植物血凝素刺激的PBMC用不同的皮质醇水平培养：0 ng / mL；100 ng / mL，代表模拟应激条件下的生理皮质醇浓度（Cort100）；和1,000 ng / mL，代表下丘脑-垂体-肾上腺轴过度活化（Cort1000）。浓度为0 ng / mL的皮质血凝素刺激的PBMC代表阳性对照，而没有皮质醇的未刺激PBMC代表阴性对照（NC）。收集游离细胞上清液以通过ELISA测定IL-6，IL-1β和IL-10。对细胞进行溴脱氧尿苷测定，以确定细胞增殖。暴露于热疗会对细胞上清液中的细胞增殖，IL-6，IL-1β和IL-10浓度产生负面影响。热疗和皮质醇水平的相互作用会影响细胞增殖和IL-10的产生。与39°C NC相比，阳性对照，Cort100和Cort100中的PBMC增殖和IL-10的产生均在43°C时下降。平均而言，Cort100处理显示出比NC高的IL-6浓度。本实验表明，模拟应激条件下的皮质醇浓度对细胞增殖和细胞因子产生的作用是在常温过程中的允许/刺激作用，而在热疗过程中则是抑制作用。这些数据证实了模拟应激条件下的皮质醇浓度可以通过在高热状态下介导细胞稳态来在绵羊的免疫系统中发挥作用。在进行免疫挑战时，高热对绵羊免疫反应的负面影响显而易见。这些数据证实了模拟应激条件下的皮质醇浓度可能通过介导热疗条件下的细胞稳态而在绵羊的免疫系统中发挥作用。在进行免疫挑战时，高热对绵羊免疫反应的负面影响显而易见。这些数据证实了模拟应激条件下的皮质醇浓度可能通过介导热疗条件下的细胞稳态而在绵羊的免疫系统中发挥作用。当执行免疫挑战时，高热对绵羊免疫反应的负面影响是显而易见的。