Department of Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
PLoS Pathog. 2012;8(11):e1003036. doi: 10.1371/journal.ppat.1003036. Epub 2012 Nov 29.
The in vivo kinetics of antigen-presenting cells (APCs) in patients with advanced and convalescent tuberculosis (TB) is not well characterized. In order to target Mycobacterium tuberculosis (MTB) peptides- and HLA-DR-holding monocytes and macrophages, 2 MTB peptide-specific CD4(+) T-cell receptor (TCR) tetramers eu and hu were successfully constructed. Peripheral blood (PBL) samples from inpatients with advanced pulmonary TB (PTB) were analyzed using flow cytometry, and the percentages of tetramer-bound CD14(+) monocytes ranged from 0.26-1.44% and 0.21-0.95%, respectively; significantly higher than those measured in PBL samples obtained from non-TB patients, healthy donors, and umbilical cords. These tetramers were also able to specifically detect macrophages in situ via immunofluorescent staining. The results of the continuous time-point tracking of the tetramer-positive rates in PBL samples from active PTB outpatients undergoing treatment show that the median percentages were at first low before treatment, increased to their highest levels during the first month, and then began to decrease during the second month until finally reaching and maintaining a relatively low level after 3-6 months. These results suggest that there is a relatively low level of MTB-specific monocytes in advanced and untreated patients. Further experiments show that MTB induces apoptosis in CD14(+) cells, and the percentage of apoptotic monocytes dramatically decreases after treatment. Therefore, the relatively low level of MTB-specific monocytes is probably related to the apoptosis or necrosis of APCs due to live bacteria and their growth. The bactericidal effects of anti-TB drugs, as well as other unknown factors, would induce a peak value during the first month of treatment, and a relatively low level would be subsequently reached and maintained until all of the involved factors reached equilibrium. These tetramers have diagnostic potential and can provide valuable insights into the mechanisms of antigen presentation and its relationship with TB infection and latent TB infection.
目前尚未很好地描述晚期和恢复期结核病（TB）患者中抗原呈递细胞（APC）的体内动力学。为了靶向含有分枝杆菌（MTB）肽和 HLA-DR 的单核细胞和巨噬细胞，成功构建了 2 种 MTB 肽特异性 CD4+T 细胞受体（TCR）四聚体 eu 和 hu。使用流式细胞术分析了来自晚期肺结核（PTB）住院患者的外周血（PBL）样本，四聚体结合的 CD14+单核细胞的百分比范围分别为 0.26-1.44%和 0.21-0.95%，明显高于非 TB 患者、健康供体和脐带 PBL 样本中的测量值。这些四聚体还能够通过免疫荧光染色特异性检测原位巨噬细胞。通过对接受治疗的活动性 PTB 门诊患者 PBL 样本中四聚体阳性率的连续时间点追踪，结果显示，中位数百分比在治疗前先低，在第一个月达到最高，然后在第二个月开始下降，直到 3-6 个月后最终达到并维持相对较低的水平。这些结果表明，在晚期和未经治疗的患者中，MTB 特异性单核细胞的水平相对较低。进一步的实验表明，MTB 诱导 CD14+细胞凋亡，治疗后凋亡单核细胞的百分比显著下降。因此，MTB 特异性单核细胞的相对低水平可能与活细菌及其生长导致的 APC 凋亡或坏死有关。抗结核药物的杀菌作用以及其他未知因素会在治疗的第一个月诱导出现峰值，随后达到并维持相对较低的水平，直到所有相关因素达到平衡。这些四聚体具有诊断潜力，可以为抗原呈递的机制及其与 TB 感染和潜伏 TB 感染的关系提供有价值的见解。
