DAO 35:13-22 (1999)  -  doi:10.3354/dao035013

Rainbow trout leucocyte activity: influence on the ectoparasitic monogenean Gyrodactylus derjavini

K. Buchmann1,*, J. Bresciani2

1Department of Veterinary Microbiology, Section of Fish Diseases, Royal Veterinary and Agricultural University, 13 Bülowsvej, DK-1870 Frederiksberg C, Denmark
2Department of Ecology and Molecular Biology, Section of Zoology, Royal Veterinary and Agricultural University, 13 Bülowsvej, DK-1870 Frederiksberg C, Denmark

ABSTRACT: The ectoparasitic monogenean Gyrodactylus derjavini from rainbow trout Oncorhynchus mykiss was exposed in vitro to macrophages isolated as peritoneal exudate cells or as pronephros cells from the host. Cells colonized the parasite especially in the mannose-rich regions in the cephalic ducts where ciliated structures were abundant. Opsonization with fresh serum, in contrast to heat-inactivated serum, enhanced colonization also on other body parts. The adverse effect of the activated macrophages towards G. derjavini was associated with a heat-labile component released from these cells to the culture medium. Analysis of substances released from the cells showed reactivity for a number of enzymes, complement factor C3, interleukin (Il-1) and reactive oxygen metabolites. Chemotaxis assays with pronephric leucocytes showed chemoattractants in G. derjavini, and the respiratory burst level of macrophages was slightly elevated due to parasite exposure. It is suggested that skin leucocytes contribute to an increased level of complement factors in the trout skin during the host response, whereby a hostile microenvironment for the parasites is created. In addition, the IL-1 production could affect mucous cell secretion and hyperplasia and add to the antiparasitic action of the epithelium. Likewise, reactive oxygen metabolites and various enzymes are likely to be involved in the skin response.

KEY WORDS: Leucocyte · Complement · Interleukin · Respiratory burst · Rainbow trout · Parasite · Monogenean · Gyrodactylus

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