Institute for Transfusion Medicine, Hannover Medical School, Hannover, Germany.
King Saud Medical City, Riyadh, Saudi Arabia.
Cell Death Dis. 2019 Mar 8;10(3):235. doi: 10.1038/s41419-019-1319-5.
Antibody-mediated rejection (AMR) is the major cause of allograft loss after solid organ transplantation. Circulating donor-specific antibodies against human leukocyte antigen (HLA), in particular HLA class II antibodies are critical for the pathogenesis of AMR via interactions with endothelial cells (ECs). To investigate the effects of HLA class II antibody ligation to the graft endothelium, a model of HLA-DR antibody-dependent stimulation was utilized in primary human ECs. Antibody ligation of HLA class II molecules in interferon-γ-treated ECs caused necrotic cell death without complement via a pathway that was independent of apoptosis and necroptosis. HLA-DR-mediated cell death was blocked by specific neutralization of antibody ligation with recombinant HLA class II protein and by lentiviral knockdown of HLA-DR in ECs. Importantly, HLA class II-mediated cytotoxicity was also induced by relevant native allele-specific antibodies from human allosera. Necrosis of ECs in response to HLA-DR ligation was mediated via hyperactivation of lysosomes, lysosomal membrane permeabilization (LMP), and release of cathepsins. Notably, LMP was caused by reorganization of the actin cytoskeleton. This was indicated by the finding that LMP and actin stress fiber formation by HLA-DR antibodies were both downregulated by the actin polymerization inhibitor cytochalasin D and inhibition of Rho GTPases, respectively. Finally, HLA-DR-dependent actin stress fiber formation and LMP led to mitochondrial stress, which was revealed by decreased mitochondrial membrane potential and generation of reactive oxygen species in ECs. Taken together, ligation of HLA class II antibodies to ECs induces necrotic cell death independent of apoptosis and necroptosis via a LMP-mediated pathway. These findings may enable novel therapeutic approaches for the treatment of AMR in solid organ transplantation.
抗体介导的排斥反应（AMR）是实体器官移植后同种异体移植物丢失的主要原因。针对人类白细胞抗原（HLA）的循环供体特异性抗体，特别是 HLA Ⅱ类抗体，通过与内皮细胞（ECs）相互作用，是 AMR 发病机制的关键。为了研究 HLA Ⅱ类抗体与移植物内皮结合对移植物的影响，利用原代人 ECs 中的 HLA-DR 抗体依赖性刺激模型进行了研究。干扰素-γ处理的 ECs 中 HLA Ⅱ类分子的抗体结合导致坏死性细胞死亡，而无需补体通过独立于凋亡和坏死性细胞死亡的途径。通过用重组 HLA Ⅱ类蛋白特异性中和抗体结合和 ECs 中 HLA-DR 的慢病毒敲低来阻断 HLA-DR 介导的细胞死亡。重要的是，来自人类同种异体血清的相关天然等位基因特异性抗体也诱导了 HLA Ⅱ类介导的细胞毒性。ECs 对 HLA-DR 结合的反应性坏死是通过溶酶体过度激活、溶酶体膜通透性（LMP）和组织蛋白酶释放介导的。值得注意的是，LMP 是由肌动蛋白细胞骨架的重排引起的。这一发现表明，LMP 和 HLA-DR 抗体形成的肌动蛋白应力纤维形成均被肌动蛋白聚合抑制剂细胞松弛素 D 和 Rho GTPases 抑制下调。最后，HLA-DR 依赖性肌动蛋白应力纤维形成和 LMP 导致线粒体应激，这表现为 ECs 中线粒体膜电位降低和活性氧的产生。总之，HLA Ⅱ类抗体与 ECs 的结合通过 LMP 介导的途径独立于凋亡和坏死性细胞死亡诱导坏死性细胞死亡。这些发现可能为实体器官移植中 AMR 的治疗提供新的治疗方法。
