Dassanayake Rohana P, Shanthalingam Sudarvili, Liu Weiguo, Casas Eduardo, Srikumaran Subramaniam
1 Department of Veterinary Microbiology and Pathology, Washington State University, PO Box 647040, Pullman, Washington 99164, USA.
2 US Department of Agriculture, Agricultural Research Service, National Animal Disease Center, 1920 Dayton Ave., Ames, Iowa 50010, USA.
J Wildl Dis. 2017 Jul;53(3):625-629. doi: 10.7589/2016-11-244. Epub 2017 Mar 21.
Bighornsheep ( Ovis canadensis ) are more susceptible to pneumonia caused by Mannheimia haemolytica than are domestic sheep ( Ovis aries ). Leukotoxin produced by M. haemolytica is the principal virulence factor involved in pneumonia pathogenesis. Although leukotoxin is cytolytic to all subsets of ruminant leukocytes, neutrophils are the most susceptible subset. Bighorn sheep neutrophils are four- to eightfold more susceptible to leukotoxin-induced cytolysis than are domestic sheep neutrophils. We hypothesized that the higher susceptibility of bighorn sheep neutrophils, in comparison to domestic sheep neutrophils, is due to higher expression of CD18, the receptor for leukotoxin on leukocytes. Our objective was to quantify CD18 expression on neutrophils of bighorn sheep and domestic sheep. Cell-surface CD18 expression on bighorn sheep and domestic sheep neutrophils was measured as antibody binding capacity of cells by flow cytometric analysis with two fluorochrome-conjugated anti-CD18 monoclonal antibodies (BAQ30A and HUH82A) and microspheres. Contrary to our expectations, CD18 expression was higher (P<0.0001) with monoclonal antibody BAQ30A and was higher (P<0.0002) as well with monoclonal antibody HUH80A on domestic sheep neutrophils in comparison to bighorn sheep neutrophils. These findings suggest that the higher in vitro susceptibility to leukotoxin of bighorn sheep neutrophils compared to domestic sheep neutrophils is not due to higher expression of the leukotoxin receptor CD18 on bighorn sheep neutrophils.
与家羊（Ovis aries）相比，大角羊（Ovis canadensis）更容易感染由溶血曼氏杆菌引起的肺炎。溶血曼氏杆菌产生的白细胞毒素是肺炎发病机制中主要的毒力因子。尽管白细胞毒素对反刍动物白细胞的所有亚群都具有细胞溶解性，但中性粒细胞是最敏感的亚群。大角羊的中性粒细胞对白细胞毒素诱导的细胞溶解的敏感性比家羊的中性粒细胞高4至8倍。我们假设，与家羊的中性粒细胞相比，大角羊的中性粒细胞更高的敏感性是由于白细胞上白细胞毒素受体CD18的表达更高。我们的目标是量化大角羊和家羊中性粒细胞上CD18的表达。通过使用两种荧光染料偶联的抗CD18单克隆抗体（BAQ30A和HUH82A）和微球进行流式细胞术分析，将大角羊和家羊中性粒细胞上的细胞表面CD18表达测量为细胞的抗体结合能力。与我们的预期相反，与大角羊的中性粒细胞相比，家羊的中性粒细胞在用单克隆抗体BAQ30A时CD18表达更高（P<0.0001），在用单克隆抗体HUH80A时也更高（P<0.0002）。这些发现表明，与家羊的中性粒细胞相比，大角羊的中性粒细胞在体外对白细胞毒素更高的敏感性并非由于大角羊中性粒细胞上白细胞毒素受体CD18的表达更高。
