title: Epidermal response of rainbow trout to Ichthyobodo necator: immunohistochemical and gene expression studies indicate a Th1-/Th2-like switch.
abstract: Infections with the parasitic flagellate Ichthyobodo necator (Henneguy, 1883) cause severe skin and gill disease in rainbow trout Oncorhynchus mykiss (Walbaum, 1792) juveniles. The epidermal disturbances including hyperplasia and mucous cell exhaustion caused by parasitization are known, but no details on specific cellular and humoral reactions have been presented. By applying gene expression methods and immunohistochemical techniques, further details of immune processes in the affected skin can be presented. A population of I. necator was established in the laboratory and used to induce an experimental infection of juvenile rainbow trout. The course of infection was followed by sampling for parasite enumeration, immunohistochemistry (IHC) and quantitative PCR (qPCR) on days 0, 5, 9 and 14 post-infection. IHC showed a significant increase in the occurrence of IgM-positive cells in the skin of the infected fish, whereas IgT-positive cells were eliminated and the number of CD8-positive cells declined. qPCR studies supported the IHC findings showing a significant increase in IgM and a decrease in the CD8 gene expression. In addition, genes encoding innate immune genes such as lysozyme, SAA and cathelicidin 2 were up-regulated. Expression of cytokines (IL-1β, IL-4/13A, IL-6, IL-8, IL-10), the cell marker CD4 and the transcription factor GATA3 showed a significant increase after infection. Cytokine profiling including up-regulation of IL-4/13A and IL-10 genes and transcription factor GATA3 connected to the proliferation of IgM producing lymphocytes suggests a partial shift towards a Th2 response associated with the I. necator infection.
authors: Laboratory of Aquatic Pathobiology, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
authors: J K
authors: JK
authors: Chettri
authors: J A
authors: JA
authors: Kuhn
authors: R M
authors: RM
authors: Jaafar
authors: P W
authors: PW
authors: Kania
authors: O S
authors: OS
authors: Møller
authors: K
authors: K
authors: Buchmann
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D004817:Epidermis / Q000276:immunology / Q000469:parasitology; D056986:Euglenozoa Infections / Q000235:genetics / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology* / Q000469:parasitology; D005786:Gene Expression Regulation; D007075:Immunoglobulin M / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry / Q000662:veterinary; D016830:Kinetoplastida / Q000502:physiology*; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss; D016133:Polymerase Chain Reaction / Q000662:veterinary; D017422:Sequence Analysis, DNA / Q000662:veterinary
chemical_list: D016207:Cytokines; D007075:Immunoglobulin M
keywords: Th2 response; fish; flagellates; immunity; immunohistochemistry; quantitative PCR