Mannheimia haemolytica and Its Leukotoxin Cause Neutrophil Extracellular Trap Formation by Bovine Neutrophils
Mannheimia haemolytica and Its Leukotoxin Cause Neutrophil Extracellular Trap Formation by Bovine Neutrophils
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DOI：
10.1128/iai.00840-10
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发表时间：
2010-11-01
影响因子：
3.1
通讯作者：
Czuprynski, Charles J.
中科院分区：
文献类型：
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作者：
Aulik, Nicole A.;Hellenbrand, Katrina M.;Czuprynski, Charles J.
溶血曼海姆氏菌是牛呼吸道疾病复合体的重要成员，其特征是大量中性粒细胞浸润到肺泡和纤维蛋白沉积。最近，一些作者报道说，人类中性粒细胞释放中性粒细胞胞外陷阱（NET），这是一种充满蛋白质的 DNA 基质，能够捕获和杀死病原体。在这里，我们证明溶血分枝杆菌的白细胞毒素 (LKT) 以 CD18 依赖性方式导致牛中性粒细胞形成 NET。使用由溶血分枝杆菌 Delta lktC 突变体产生的未酰化、无细胞毒性的 pro-LKT，我们发现，尽管缺乏细胞毒性，但未酰化的 pro-LKT 的结合刺激了 NET 的形成。抑制牛中性粒细胞上 LKT 与淋巴细胞功能相关抗原 1 (LFA-1) 的 CD18 链的结合，可减少响应 LKT 或溶血支原体细胞的 NET 形成。进一步的研究表明，响应溶血分枝杆菌而形成的 NET 能够捕获并杀死部分细菌细胞。通过共焦显微镜以及扫描和透射电子显微镜证实了NET的形成。预先将牛中性粒细胞暴露于 LKT 可以增强随后对牛 NET 中溶血支原体细胞的捕获和杀死。了解溶血支原体及其 LKT 引起的 NET 形成，为了解中性粒细胞如何促进牛呼吸道疾病的发病机制提供了新的视角。
Mannheimia haemolytica is an important member of the bovine respiratory disease complex, which is characterized by abundant neutrophil infiltration into the alveoli and fibrin deposition. Recently several authors have reported that human neutrophils release neutrophil extracellular traps (NETs), which are protein-studded DNA matrices capable of trapping and killing pathogens. Here, we demonstrate that the leukotoxin (LKT) of M. haemolytica causes NET formation by bovine neutrophils in a CD18-dependent manner. Using an unacylated, noncytotoxic pro-LKT produced by an Delta lktC mutant of M. haemolytica, we show that binding of unacylated pro-LKT stimulates NET formation despite a lack of cytotoxicity. Inhibition of LKT binding to the CD18 chain of lymphocyte function-associated antigen 1 (LFA-1) on bovine neutrophils reduced NET formation in response to LKT or M. haemolytica cells. Further investigation revealed that NETs formed in response to M. haemolytica are capable of trapping and killing a portion of the bacterial cells. NET formation was confirmed by confocal microscopy and by scanning and transmission electron microscopy. Prior exposure of bovine neutrophils to LKT enhanced subsequent trapping and killing of M. haemolytica cells in bovine NETs. Understanding NET formation in response to M. haemolytica and its LKT provides a new perspective on how neutrophils contribute to the pathogenesis of bovine respiratory disease.