Jeyaseelan S, Hsuan S L, Kannan M S, Walcheck B, Wang J F, Kehrli M E, Lally E T, Sieck G C, Maheswaran S K
Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA.
Infect Immun. 2000 Jan;68(1):72-9. doi: 10.1128/IAI.68.1.72-79.2000.
Pasteurella (Mannheimia) haemolytica leukotoxin (Lkt) causes cell type- and species-specific effects in ruminant leukocytes. Recent studies indicate that P. haemolytica Lkt binds to bovine CD18, the common subunit of all beta2 integrins. We designed experiments with the following objectives: to identify which member of the beta2 integrins is a receptor for Lkt; to determine whether Lkt binding to the receptor is target cell (bovine leukocytes) specific; to define the relationships between Lkt binding to the receptor, calcium elevation, and cytolysis; and to determine whether a correlation exists between Lkt receptor expression and the magnitude of target cell cytolysis. We compared Lkt-induced cytolysis in neutrophils from control calves and from calves with bovine leukocyte adhesion deficiency (BLAD), because neutrophils from BLAD-homozygous calves exhibit reduced beta2 integrin expression. The results demonstrate for the first time that Lkt binds to bovine CD11a and CD18 (lymphocyte function-associated antigen 1 [LFA-1]). The binding was abolished by anti-CD11a or anti-CD18 monoclonal antibody (MAb). Lkt-induced calcium elevation in bovine alveolar macrophages (BAMs) was inhibited by anti-CD11a or anti-CD18 MAb (65 to 94% and 37 to 98%, respectively, at 5 and 50 Lkt units per ml; P < 0.05). Lkt-induced cytolysis in neutrophils and BAMs was also inhibited by anti-CD11a or anti-CD18 MAb in a concentration-dependent manner. Lkt bound to porcine LFA-1 but did not induce calcium elevation or cytolysis. In neutrophils from BLAD calves, Lkt-induced cytolysis was decreased by 44% compared to that of neutrophils from control calves (P < 0.05). These results indicate that LFA-1 is a Lkt receptor, Lkt binding to LFA-1 is not target cell specific, Lkt binding to bovine LFA-1 correlates with calcium elevation and cytolysis, and bovine LFA-1 expression correlates with the magnitude of Lkt-induced target cell cytolysis.
溶血巴斯德氏菌（曼氏杆菌属）白细胞毒素（Lkt）在反刍动物白细胞中会引起细胞类型和物种特异性效应。最近的研究表明，溶血巴斯德氏菌Lkt与牛CD18结合，CD18是所有β2整合素的共同亚基。我们设计了以下实验目标：确定β2整合素中的哪个成员是Lkt的受体；确定Lkt与受体的结合是否具有靶细胞（牛白细胞）特异性；明确Lkt与受体结合、钙升高和细胞溶解之间的关系；以及确定Lkt受体表达与靶细胞细胞溶解程度之间是否存在相关性。我们比较了对照犊牛和患有牛白细胞黏附缺陷（BLAD）的犊牛中性粒细胞中Lkt诱导的细胞溶解情况，因为来自BLAD纯合子犊牛的中性粒细胞β2整合素表达降低。结果首次证明Lkt与牛CD11a和CD18（淋巴细胞功能相关抗原1 [LFA-1]）结合。抗CD11a或抗CD18单克隆抗体（MAb）可消除这种结合。抗CD11a或抗CD18 MAb可抑制Lkt诱导的牛肺泡巨噬细胞（BAM）钙升高（每毫升5和50个Lkt单位时，分别为65%至94%和37%至98%；P<0.05）。抗CD11a或抗CD18 MAb也以浓度依赖的方式抑制Lkt诱导的中性粒细胞和BAM细胞溶解。Lkt与猪LFA-1结合，但不诱导钙升高或细胞溶解。与对照犊牛的中性粒细胞相比，BLAD犊牛的中性粒细胞中Lkt诱导的细胞溶解降低了44%（P<0.05）。这些结果表明，LFA-1是Lkt受体，Lkt与LFA-1的结合不是靶细胞特异性的，Lkt与牛LFA-1的结合与钙升高和细胞溶解相关，并且牛LFA-1表达与Lkt诱导的靶细胞细胞溶解程度相关。
