title: Level of galactosylation determines cryoglobulin activity of murine IgG3 monoclonal rheumatoid factor.
abstract: Autoantibodies of the cryoprecipitating IgG3 isotype have been shown to play a significant role in the development of murine lupus-like autoimmune syndrome. At present, the structural basis of IgG3 cryoprecipitation and its role in autoantibody pathogenicity remain to be defined. Using molecular variants of an IgG3 monoclonal rheumatoid factor, 6-19, derived from an autoimmune MRL-Fas(lpr) mouse, we have investigated the implication of charged residues in the heavy-chain variable (VH) region, potential CH3-linked oligosaccharides, and galactosylation of CH2-linked oligosaccharides in its cryoglobulin activity. The cryoglobulin activity of the IgG3 6-19 mutant bearing more negatively charged residues at VH 6 and 23 was found to be reduced but still highly significant, whereas that of the mutant lacking a potential CH3 glycosylation site remained unchanged. In marked contrast, IgG3 6-19 variants obtained from 6-19 heavy-chain transgenic mice displayed barely detectable cryoglobulin activity associated with an increased level of galactosylation in the CH2 oligosaccharide side chains. Thus, our data strongly suggest that the cryoglobulin activity of IgG3 6-19 autoantibody is critically determined by levels of galactosylation in the CH2 oligosaccharide side chains, whereas VH residues play a secondary role in 6-19 IgG3 cryoglobulin activity.
authors.affiliation: Department of Pathology, Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Aki
authors.initials: A
authors.lastname: Kuroki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kuroda
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kikuchi
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lajaunias
authors.forename: Thierry
authors.initials: T
authors.lastname: Fulpius
authors.forename: Yves
authors.initials: Y
authors.lastname: Pastore
authors.forename: Liliane
authors.initials: L
authors.lastname: Fossati-Jimack
authors.forename: Luc
authors.initials: L
authors.lastname: Reininger
authors.forename: Toho
authors.initials: T
authors.lastname: Toda
authors.forename: Munehiro
authors.initials: M
authors.lastname: Nakata
authors.forename: Naoya
authors.initials: N
authors.lastname: Kojima
authors.forename: Tsuguo
authors.initials: T
authors.lastname: Mizuochi
authors.forename: Shozo
authors.initials: S
authors.lastname: Izui
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000235:genetics; D011232:Chemical Precipitation; D003080:Cold Temperature; D003450:Cryoglobulins / Q000737:chemistry* / Q000235:genetics; D019281:Dimerization; D005690:Galactose; D006031:Glycosylation; D007074:Immunoglobulin G / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D012217:Rheumatoid Factor / Q000737:chemistry* / Q000235:genetics; D019076:Transgenes
chemical_list: D000911:Antibodies, Monoclonal; D003450:Cryoglobulins; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D012217:Rheumatoid Factor; D005690:Galactose