title: MHC class II invariant chain homologues in rainbow trout (Oncorhynchus mykiss).
abstract: The MHC class II invariant chain (Ii or CD74) in higher vertebrates is necessary for normal MHC class II loading in endosomal compartments. Detection of an Ii chain in fish would greatly support the idea that MHC class II function in fish and higher vertebrates is similar. Before this study only Ii homologues had been reported in fish that are unlikely to perform true Ii function. In the present study two Ii-like genes, Onmy-Iclp-1 and Onmy-Iclp-2, were detected in rainbow trout. Conservation of elements, particularly in Onmy-Iclp-1, suggests that the encoded proteins may be involved in MHC class II transport and peptide loading as is the Ii protein. The expression pattern of both rainbow trout genes was similar to that of the MHC class II beta chain, with strong expression in the lymphoid tissues, gills and intestine. Analysis of separated peripheral blood leucocyte fractions indicated that expression of Onmy-Iclp-1, Onmy-Iclp-2 and the MHC class II beta chain were all highest in B lymphocytes. This agrees with the expectation that the functions of the products of the new genes are closely associated with MHC class II. It is interesting why in rainbow trout there are two proteins that may function similar to Ii in higher vertebrates.
authors.affiliation: Inland Station/National Research Institute of Aquaculture, Fisheries Research Agency, Tamaki, Mie, 519-0423, Japan.
authors.forename: Johannes Martinus
authors.initials: JM
authors.lastname: Dijkstra
authors.forename: Ikunari
authors.initials: I
authors.lastname: Kiryu
authors.forename: Bernd
authors.initials: B
authors.lastname: Köllner
authors.forename: Yasutoshi
authors.initials: Y
authors.lastname: Yoshiura
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Ototake
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D005880:Gills / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D007422:Intestines / Q000276:immunology; D008221:Lymphoid Tissue / Q000276:immunology; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000276:immunology*; D010802:Phylogeny; D012313:RNA / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D016415:Sequence Alignment
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D000949:Histocompatibility Antigens Class II; C045084:invariant chain; D012313:RNA