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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Ruminant Diseases and Immunology Research » Research » Publications at this Location » Publication #333266
Title: Differential susceptibility of bighorn sheep and domestic sheep neutrophils to Mannheimia haemolytica leukotoxin is not due to differential expression of cell surface CD18

Author
item Dassanayake, Rohana
item SHANTHALINGAM, S - Washington State University
item LIU, W - Washington State University
item Knowles Jr, Donald
item Casas, Eduardo
item SRIKUMARAN, S - Washington State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/7/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Bighorn sheep (BHS) are more susceptible to pneumonia caused by Mannheimia haemolytica (M. haemolytica) than are domestic sheep (DS). Leukotoxin produced by M. haemolytica is accepted as the critical virulence factor for BHS, based on the fact that Lkt-deletion mutants do not cause death of BHS. Although Lkt is cytolytic to all subsets of ruminant leukocytes, neutrophils are the most susceptible subset. BHS neutrophils are 4-8 times more susceptible to Lkt than are DS neutrophils. We hypothesized that the higher susceptibility of BHS neutrophils, in comparison to DS neutrophils, is due to higher expression of CD18, the receptor for Lkt on leukocytes. The objective of this study, therefore, was to quantify CD18 expression on neutrophils of BHS and DS. The expression of cell-surface CD18 on BHS and DS neutrophils was measured as antibody binding capacity (ABC) of cells by flow cytometric analysis with two fluorochrome-conjugated anti-CD18 mAbs (BAQ30A and HUH82A) and microspheres. Contrary to our expectation, significantly higher (P less than 0.0001) CD18 expression was observed with mAb BAQ30A on DS neutrophils (98207 plus or minus 3010 ABC) in comparison to BHS neutrophils (71487 plus or minus 3010 ABC). Similarly, significantly higher (P less than 0.0002) CD18 expression was observed with mAb HUH80A on DS neutrophils (120,289 plus or minus 4207 ABC) in comparison to BHS neutrophils (89173 plus or minus 4207 ABC). These findings suggest that the higher susceptibility of BHS neutrophils to M. haemolytica Lkt, in comparison to DS neutrophils, is not due to higher expression of the Lkt receptor CD18 on BHS neutrophils.