title: Anti-Hinge Antibodies Recognize IgG Subclass- and Protease-Restricted Neoepitopes.
abstract: Anti-hinge Abs (AHAs) target neoepitopes exposed after proteolytic cleavage of IgG. In this study, we explored the diversity of protease- and IgG subclass-restricted AHAs and their potential as immunological markers in healthy donors (HDs) and patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE). AHA reactivity against IgG-degrading enzyme of Streptococcus pyogenes (IdeS)- or pepsin-generated F(ab')2fragments of all four human IgG subclasses was determined. AHA reactivity against one or more out of eight F(ab')2targets was found in 68% (68 of 100) of HDs, 69% (68 of 99) of SLE patients, and 81% (79 of 97) of RA patients. Specific recognition of hinge epitopes was dependent on IgG subclass and protease used to create the F(ab')2targets, as confirmed by inhibition experiments with F(ab')2fragments and hinge peptides. Reactivity against IdeS-generated F(ab')2targets was found most frequently, whereas reactivity against pepsin-generated F(ab')2targets better discriminated between RA and HDs or SLE, with significantly higher AHA levels against IgG1/3/4. In contrast, AHA levels against pepsin-cleaved IgG2 were comparable. No reactivity against IdeS-generated IgG2-F(ab')2s was detected. The most discriminatory AHA reactivity in RA was against pepsin-cleaved IgG4, with a 35% prevalence, ≥5.8-fold higher than in HDs/SLE, and significantly higher levels (p < 0.0001). Cross-reactivity for F(ab')2s generated from different IgG subclasses was only observed for subclasses having homologous F(ab')2C termini (IgG1/3/4). For IgG2, two pepsin cleavage sites were identified; anti-hinge reactivity was restricted to only one of these. In conclusion, AHAs specifically recognize IgG subclass- and protease-restricted hinge neoepitopes. Their protease-restricted specificity suggests that different AHA responses developed under distinct inflammatory or infectious conditions and may be markers of, and participants in, such processes.
authors.affiliation: Amsterdam Rheumatology and Immunology Center, Reade, 1056 AB Amsterdam, the Netherlands; w.falkenburg@sanquin.nl.|Department of Immunopathology, Sanquin Research, 1006 AN Amsterdam, the Netherlands.
authors.forename: Willem J J
authors.initials: WJ
authors.lastname: Falkenburg
authors.affiliation: Amsterdam Rheumatology and Immunology Center, Reade, 1056 AB Amsterdam, the Netherlands.|Amsterdam Rheumatology and Immunology Center, Academic Medical Center, 1100 DD Amsterdam, the Netherlands.
authors.forename: Dirkjan
authors.initials: D
authors.lastname: van Schaardenburg
authors.affiliation: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands.
authors.forename: Pleuni
authors.initials: P
authors.lastname: Ooijevaar-de Heer
authors.affiliation: Amsterdam Rheumatology and Immunology Center, VU University Medical Center, 1007 MB Amsterdam, the Netherlands; and.
authors.forename: Michel W P
authors.identifier: 0000-0002-4982-3505
authors.initials: MW
authors.lastname: Tsang-A-Sjoe
authors.affiliation: Amsterdam Rheumatology and Immunology Center, VU University Medical Center, 1007 MB Amsterdam, the Netherlands; and.
authors.forename: Irene E M
authors.identifier: 0000-0002-5441-3420
authors.initials: IE
authors.lastname: Bultink
authors.affiliation: Amsterdam Rheumatology and Immunology Center, VU University Medical Center, 1007 MB Amsterdam, the Netherlands; and.
authors.forename: Alexandre E
authors.initials: AE
authors.lastname: Voskuyl
authors.affiliation: Department of Experimental Immunohematology, Sanquin Research, 1006 AN Amsterdam, the Netherlands.
authors.forename: Arthur E H
authors.initials: AE
authors.lastname: Bentlage
authors.affiliation: Department of Experimental Immunohematology, Sanquin Research, 1006 AN Amsterdam, the Netherlands.
authors.forename: Gestur
authors.identifier: 0000-0001-5621-003X
authors.initials: G
authors.lastname: Vidarsson
authors.affiliation: Amsterdam Rheumatology and Immunology Center, Reade, 1056 AB Amsterdam, the Netherlands.
authors.forename: Gertjan
authors.initials: G
authors.lastname: Wolbink
authors.affiliation: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands.
authors.forename: Theo
authors.initials: T
authors.lastname: Rispens
mesh_terms: D000918:Antibody Specificity; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000276:immunology*; D013058:Mass Spectrometry; D010447:Peptide Hydrolases; D020349:Surface Plasmon Resonance
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D018985:Epitopes, B-Lymphocyte; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D010447:Peptide Hydrolases