title: Minor effect of depletion of resident macrophages from peritoneal cavity on resistance of common carp Cyprinus carpio to blood flagellates.
abstract: Carp Cyprinus carpio macrophages were depleted by intraperitoneal (i.p.) injection of clodronate-liposomes for the in vivo study of the effect of macrophage depletion on the resistance of carp to infection with blood flagellate parasites. Clodronate released inside the cell induces apoptosis of (murine) macrophages. Following i.p. injection of carp with liposomes alone, but not with Trypanoplasma borreli, neutrophilic granulocytes rapidly migrated from the head kidney to the peritoneal cavity. The majority of liposomes in the peritoneal cavity were not taken up by newly arrived neutrophilic granulocytes, however, but by resident macrophages. After 2 i.p. injections of clodronate-liposomes, the percentage of macrophages present in the peritoneal cavity was significantly reduced, as evaluated by flow cytometry. Macrophage-depleted carp that were infected i.p. with T. borreli suffered from high mortality. However, these fish did not show lethal parasitaemia but did show clear bacteraemia. Macrophage-depleted carp that were infected i.p. with Trypanosoma carassii showed a minor increase in parasitaemia. In addition, macrophage-depleted carp, immune to T. borreli as a result of having survived a prior infection, remained immune to i.p. reinfection with T. borreli. Succesful depletion of peritoneal macrophages seemed to have a minor effect on the resistance of carp against blood flagellates. However, carp macrophages are essential as a first line of defence against (bacterial) infection.
authors.affiliation: Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands.
authors.forename: Jeroen P J
authors.initials: JP
authors.lastname: Saeij
authors.forename: Adrie
authors.initials: A
authors.lastname: Groeneveld
authors.forename: Nico
authors.initials: N
authors.lastname: Van Rooijen
authors.forename: Olga L M
authors.initials: OL
authors.lastname: Haenen
authors.forename: Geert F
authors.initials: GF
authors.lastname: Wiegertjes
mesh_terms: D000818:Animals; D002347:Carps; D004002:Clodronic Acid / Q000494:pharmacology*; D056890:Eukaryota / Q000276:immunology*; D005393:Fish Diseases / Q000097:blood* / Q000276:immunology / Q000469:parasitology; D005434:Flow Cytometry; D007113:Immunity, Innate / Q000187:drug effects*; D008081:Liposomes; D017737:Macrophages, Peritoneal / Q000276:immunology*; D011528:Protozoan Infections / Q000276:immunology; D011529:Protozoan Infections, Animal
chemical_list: D008081:Liposomes; D004002:Clodronic Acid