title: In situ localisation of major histocompatibility complex class I and class II and CD8 positive cells in infectious salmon anaemia virus (ISAV)-infected Atlantic salmon.
abstract: It is assumed that the mobilisation of a strong cellular immune response is important for the survival of Atlantic salmon infected with infectious salmon anaemia virus (ISAV). In this study, the characterisation of immune cell populations in tissues of non-ISAV infected Atlantic salmon and during the early viraemia of ISAV was undertaken. Immunohistochemical investigations of spleen, head kidney and gills using monoclonal antibodies against recombinant proteins from MHC I, II and CD8 were performed on tissues from Atlantic salmon collected day 17 post-challenge in a cohabitant infection model. The localisations of MHC I and II in control salmon were consistent with previous reports but this study presents novel observations on the distribution of CD8 labelled cell populations in Atlantic salmon including the description of significant mucosal populations in the gills. The distribution of MHC I, MHC II and CD8 positive cell populations differed between control salmon and cohabitant salmon in the early stages of ISAV infection. The changes in MHC I labelled cells differed between organs in ISAV cohabitants but all investigated organs showed a decreased presence of MHC II labelled cells. Together with a clustering of CD8 labelled cells in the head kidney and a reduced presence of CD8 labelled cells in the gills, these observations support the early mobilisation of cellular immunity in the response of Atlantic salmon to ISAV infection. However, differences between the present study and the findings from studies investigating immune gene mRNA expression during ISAV infection suggest that viral strategies to interfere with protein expression and circumvent the host immune response could be operative in the early response to ISAV infection.
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, 0033 Oslo, Norway. dyveke.hetland@veths.no
authors.forename: Dyveke Lem
authors.initials: DL
authors.lastname: Hetland
authors.forename: Sven Martin
authors.initials: SM
authors.lastname: Jørgensen
authors.forename: Karsten
authors.initials: K
authors.lastname: Skjødt
authors.forename: Ole Bendik
authors.initials: OB
authors.lastname: Dale
authors.forename: Knut
authors.initials: K
authors.lastname: Falk
authors.forename: Cheng
authors.initials: C
authors.lastname: Xu
authors.forename: Aase B
authors.initials: AB
authors.lastname: Mikalsen
authors.forename: Unni
authors.initials: U
authors.lastname: Grimholt
authors.forename: Tor
authors.initials: T
authors.lastname: Gjøen
authors.forename: Charles McL
authors.initials: CM
authors.lastname: Press
mesh_terms: D000818:Animals; D016827:CD8 Antigens / Q000235:genetics / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D005393:Fish Diseases / Q000276:immunology* / Q000821:virology; D005805:Genes, MHC Class I / Q000276:immunology*; D005802:Genes, MHC Class II / Q000276:immunology*; D005880:Gills / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000235:genetics / Q000276:immunology; D046829:Isavirus / Q000276:immunology; D007668:Kidney / Q000276:immunology; D009976:Orthomyxoviridae Infections / Q000276:immunology* / Q000821:virology; D020317:Salmo salar / Q000276:immunology*; D013154:Spleen / Q000276:immunology
chemical_list: D016827:CD8 Antigens; D007132:Immunoglobulin Isotypes