DataSheet_1_Low T-cell reactivity to TDP-43 peptides in ALS.pdf

BackgroundDysregulation of the immune system in amyotrophic lateral sclerosis (ALS) includes changes in T-cells composition and infiltration of T cells in the brain and spinal cord. Recent studies have shown that cytotoxic T cells can directly induce motor neuron death in a mouse model of ALS and that T cells from ALS patients are cytotoxic to iPSC-derived motor neurons from ALS patients. Furthermore, a clonal expansion to unknown epitope(s) was recently found in familial ALS and increased peripheral and intrathecal activation of cytotoxic CD8+ T cells in sporadic ALS.
ResultsHere, we show an increased activation of peripheral T cells from patients with sporadic ALS by IL-2 treatment, suggesting an increase of antigen-experienced T cells in ALS blood. However, a putative antigen for T-cell activation in ALS has not yet been identified. Therefore, we investigated if peptides derived from TDP-43, a key protein in ALS pathogenesis, can act as epitopes for antigen-mediated activation of human T cells by ELISPOT and flow cytometry. We found that TDP-43 peptides induced only a weak MHCI or MHCII-restricted activation of both naïve and antigen-experienced T cells from healthy controls and ALS patients. Interestingly, we found less activation in T cells from ALS patients to TDP-43 and control stimuli. Furthermore, we found no change in the levels of naturally occurring auto-antibodies against full-length TDP-43 in ALS.
ConclusionOur data suggests a general increase in antigen-experienced T cells in ALS blood, measured by in-vitro culture with IL-2 for 14 days. Furthermore, it suggests that TDP-43 is a weak autoantigen.

研究背景：肌萎缩侧索硬化症（amyotrophic lateral sclerosis, ALS）患者的免疫系统失调表现为T细胞组成改变，以及T细胞在脑与脊髓中的浸润。近期研究证实，细胞毒性T细胞可在ALS小鼠模型中直接诱导运动神经元死亡，且ALS患者的T细胞对患者自身诱导多能干细胞（induced pluripotent stem cell, iPSC）衍生的运动神经元具有细胞毒性。此外，研究人员近期在家族性ALS患者中发现了针对未知表位的克隆扩增现象，且散发性ALS患者的外周血及鞘内细胞毒性CD8+ T细胞激活水平升高。

研究结果：本研究通过体外14天白细胞介素-2（interleukin-2, IL-2）培养的检测方法发现，散发性ALS患者外周血T细胞的激活水平升高，提示ALS患者血液中抗原致敏T细胞比例增加。但目前尚未明确介导ALS患者T细胞激活的潜在抗原。为此，本研究通过酶联免疫斑点（enzyme-linked immunospot assay, ELISPOT）与流式细胞术，探究了ALS发病机制关键蛋白TDP-43的衍生肽段是否可作为抗原表位介导人类T细胞激活。结果显示，TDP-43肽段仅能在健康对照者及ALS患者的初始T细胞与抗原致敏T细胞中诱导微弱的MHCI或MHCII限制性激活。值得注意的是，ALS患者的T细胞对TDP-43及对照刺激的激活水平更低。此外，本研究未检测到ALS患者体内针对全长TDP-43的天然自身抗体水平存在显著变化。

研究结论：本研究数据表明，通过体外IL-2培养14天的检测方法，可发现ALS患者血液中抗原致敏T细胞比例普遍升高。此外，研究结果提示TDP-43是一种弱自身抗原。