title: Lymphocyte function-associated antigen 1 is a receptor for Pasteurella haemolytica leukotoxin in bovine leukocytes.
abstract: 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.
authors.affiliation: Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA.
authors.forename: S
authors.initials: S
authors.lastname: Jeyaseelan
authors.forename: S L
authors.initials: SL
authors.lastname: Hsuan
authors.forename: M S
authors.initials: MS
authors.lastname: Kannan
authors.forename: B
authors.initials: B
authors.lastname: Walcheck
authors.forename: J F
authors.initials: JF
authors.lastname: Wang
authors.forename: M E
authors.initials: ME
authors.lastname: Kehrli
authors.forename: E T
authors.initials: ET
authors.lastname: Lally
authors.forename: G C
authors.initials: GC
authors.lastname: Sieck
authors.forename: S K
authors.initials: SK
authors.lastname: Maheswaran
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins / Q000378:metabolism* / Q000633:toxicity; D018821:CD18 Antigens / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002448:Cell Adhesion / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D005098:Exotoxins / Q000378:metabolism* / Q000633:toxicity; D005260:Female; D018922:HL-60 Cells; D006801:Humans; D066298:In Vitro Techniques; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D016978:Mannheimia haemolytica / Q000276:immunology* / Q000472:pathogenicity; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D013552:Swine
chemical_list: D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D018821:CD18 Antigens; D005098:Exotoxins; D016169:Lymphocyte Function-Associated Antigen-1; C018579:leukotoxin; D002118:Calcium