Previous studies mainly focused on the inflammatory responses caused by Mycoplasma gallisepticum (MG) in the chicken respiratory mucosa, setting the stage for chronic infection and disease manifestation. However, the underlying mechanism is still unknown. Spleen and thymus are important immune organs, which play a critical role in eliciting protective immune responses to ensure healing process and elimination of harmful stimuli. In the present study, the effects of MG infection on chicken spleen and thymus were investigated. The results showed that MG infection reduced antioxidant activities and induced oxidative stress in the spleen and thymus tissues. Histological examination showed normal morphology of chicken spleen and thymus in control group compared to MG infection group. In contrast, increased number of necrotic and nuclear debris, lymphocytolysis, prominent reticuloepithelial cells and loose arrangement of cells in the spleen and thymus were seen in MG-infected chickens. Ultrastructural analysis indicated nuclear and mitochondrial damage including mitochondrial swelling, deformation of nuclear membrane and congestion of chromatin material in MG infection group. The mRNA and protein expression of apoptosis-related genes were significantly upregulated in the spleen and thymus of MG-infected chickens compared to control group. Moreover, Terminal deoxynucleotidyl transferase–mediated dUTP nick endlabeling (TUNEL) assay results suggested that MG infection increased the number of positive-stained nuclei in the spleen and thymus. Meanwhile, the mRNA expression of mitochondrial dynamics in the spleen and thymus were altered by MG infection. In summary, these results showed that MG induced oxidative stress and apoptosis, which could be the possible causes associated with the immune damage, structural impairment and disease pathogenesis of MG infection.

以往的研究主要集中在鸡毒支原体引起的炎症反应上(MG) 在鸡呼吸道黏膜中，为慢性感染和疾病表现奠定了基础。然而，潜在的机制仍然未知。脾脏和胸腺是重要的免疫器官，在引发保护性免疫反应以确保愈合过程和消除有害刺激方面发挥关键作用。在本研究中，研究了 MG 感染对鸡脾脏和胸腺的影响。结果表明，MG感染会降低脾脏和胸腺组织的抗氧化活性并诱导氧化应激。与MG感染组相比，组织学检查显示对照组鸡脾脏和胸腺形态正常。相反，坏死和核碎片、淋巴细胞溶解、MG感染鸡可见明显的网状上皮细胞和脾脏和胸腺中细胞排列松散。超微结构分析表明MG感染组的核和线粒体损伤包括线粒体肿胀、核膜变形和染色质物质充血。与对照组相比，MG感染鸡的脾脏和胸腺中凋亡相关基因的mRNA和蛋白表达显着上调。此外，末端脱氧核苷酸转移酶介导的 dUTP 缺口末端标记 (TUNEL) 测定结果表明，MG 感染增加了脾脏和胸腺中阳性染色的细胞核数量。同时，MG感染改变了脾脏和胸腺中线粒体动力学的mRNA表达。总之，