Prasad Sujata, Hu Shuxian, Sheng Wen S, Singh Amar, Lokensgard James R
Neuroimmunology Laboratory, Center for Infectious Diseases and Microbiology Translational Research, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, 55455, United States of America.
PLoS One. 2015 Dec 31;10(12):e0145457. doi: 10.1371/journal.pone.0145457. eCollection 2015.
Accumulation and retention of regulatory T-cells (Tregs) has been reported within post viral-encephalitic brains, however, the full extent to which these cells modulate neuroinflammation is yet to be elucidated. Here, we used Foxp3-DTR (diphtheria toxin receptor) knock-in transgenic mice, which upon administration of low dose diphtheria toxin (DTx) results in specific deletion of Tregs. We investigated the proliferation status of various immune cell subtypes within inflamed central nervous system (CNS) tissue. Depletion of Tregs resulted in increased proliferation of both CD8+ and CD4+ T-cell subsets within the brain at 14 d post infection (dpi) when compared to Treg-sufficient animals. At 30 dpi, while proliferation of CD8+ T-cells was controlled within brains of both Treg-depleted and undepleted mice, proliferation of CD4+ T-cells remained significantly enhanced with DTx-treatment. Previous studies have demonstrated that Treg numbers within the brain rebound following DTx treatment to even higher numbers than in untreated animals. Despite this rebound, CD8+ and CD4+ T-cells proliferated at a higher rate when compared to that of Treg-sufficient mice, thus maintaining sustained neuroinflammation. Furthermore, at 30 dpi we found the majority of CD8+ T-cells were CD127hi KLRG1- indicating that the cells were long lived memory precursor cells. These cells showed marked elevation of CD103 expression, a marker of tissue resident-memory T-cells (TRM) in the CNS, in untreated animals when compared to DTx-treated animals suggesting that generation of TRM is impaired upon Treg depletion. Moreover, the effector function of TRM as indicated by granzyme B production in response to peptide re-stimulation was found to be more potent in Treg-sufficient animals. Taken together, our findings demonstrate that Tregs limit neuroinflammatory responses to viral infection by controlling cell proliferation and may direct a larger proportion of lymphocytes within the brain to be maintained as TRM cells.
已有报道称，在病毒性脑炎后的脑内存在调节性T细胞（Tregs）的积累和滞留，然而，这些细胞调节神经炎症的完整程度尚待阐明。在此，我们使用了Foxp3-DTR（白喉毒素受体）基因敲入转基因小鼠，给予低剂量白喉毒素（DTx）后，Tregs会被特异性清除。我们研究了炎症性中枢神经系统（CNS）组织内各种免疫细胞亚型的增殖状态。与Tregs充足的动物相比，在感染后14天（dpi），Tregs的清除导致脑内CD8+和CD4+ T细胞亚群的增殖增加。在感染后30天，虽然在Tregs清除和未清除的小鼠脑内，CD8+ T细胞的增殖均受到控制，但DTx处理后，CD4+ T细胞的增殖仍显著增强。先前的研究表明，DTx处理后脑内的Tregs数量会反弹，甚至比未处理动物的数量更高。尽管有这种反弹，但与Tregs充足的小鼠相比，CD8+和CD4+ T细胞的增殖速度更高，从而维持了持续的神经炎症。此外，在感染后30天，我们发现大多数CD8+ T细胞为CD127hi KLRG1-，表明这些细胞是长寿记忆前体细胞。与DTx处理的动物相比，在未处理的动物中，这些细胞显示出CD103表达显著升高，CD103是中枢神经系统中组织驻留记忆T细胞（TRM）的标志物，这表明Tregs清除后TRM的生成受损。此外，在Tregs充足的动物中，经肽再刺激后由颗粒酶B产生所表明的TRM效应功能更强。综上所述，我们的研究结果表明，Tregs通过控制细胞增殖来限制对病毒感染的神经炎症反应，并可能引导脑内更大比例的淋巴细胞维持为TRM细胞。
