title: Killing of Edwardsiella ictaluri by macrophages from channel catfish immune and susceptible to enteric septicemia of catfish.
abstract: The role of peritoneal macrophages in immunity to enteric septicemia of catfish (ESC) after infection with live Edwardsiella ictaluri was investigated. Channel catfish macrophage-mediated bacteriocidal activity was dependent on the macrophage:bacteria ratio. Ratios of 1:1 to 1:12 exhibited significant differences (P < or = 0.05) in killing between macrophages from immune fish when compared to killing by macrophages from susceptible fish at 2.5 h. At 5 h, macrophages from immune fish were capable of effective killing (83.3%) at a 1:24 effector:target ratio, whereas macrophages from susceptible fish killed significantly (P < or = 0.05) less (56.9%). Macrophage bacteriocidal activity was significantly greater (P < or = 0.05) in macrophages from individual immune fish (93.4%) compared to macrophages from individual susceptible fish (85.4%). The kinetics of macrophage killing showed a linear increase in bacteriocidal activity from 1 to 3 h. Opsonization with immune serum enabled macrophages from immune fish to kill bacteria more effectively (93.8 vs. 75.9%) at 2.5 h. Opsonization of E. ictaluri with immune serum significantly suppressed the killing ability of macrophages from susceptible fish (46.2%) at 2.5 h. The results suggest that macrophages from fish immune to ESC had a greater capacity to kill E. ictaluri than macrophages from susceptible fish especially when E. ictaluri were opsonized with anti-E. ictaluri antibody.
authors.affiliation: United States Department of Agriculture, Fish Disease and Parasite Research Laboratory, Auburn, AL 36830, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Shoemaker
authors.forename: P H
authors.initials: PH
authors.lastname: Klesius
authors.forename: J A
authors.initials: JA
authors.lastname: Plumb
mesh_terms: D000818:Animals; D016470:Bacteremia / Q000276:immunology / Q000662:veterinary*; D005393:Fish Diseases / Q000276:immunology*; D006090:Gram-Negative Bacteria / Q000276:immunology*; D016905:Gram-Negative Bacterial Infections / Q000276:immunology*; D007059:Ictaluridae / Q000276:immunology*; D066298:In Vitro Techniques; D007700:Kinetics; D017737:Macrophages, Peritoneal / Q000276:immunology*; D009895:Opsonin Proteins / Q000378:metabolism; D010587:Phagocytosis
chemical_list: D009895:Opsonin Proteins