title: Autoantibodies against mono- and tri-methylated lysine display similar but also distinctive characteristics.
abstract: Autoantibodies can be either harmful or beneficial to the body. The beneficial autoantibodies play important roles in immunosurveillance, clearance of body waste and maintenance of immune homeostasis. Despite their importance, however, people's knowledge on the protective autoantibodies is still very limited. In the current study, we examined two autoantibodies that recognized epitopes with only one amino acid. One was against mono-methylated lysine (Kme) and the other was against tri-methylated lysine (Kme3). We found that the antibodies were highly specific and not polyreactive. They did not cross-react each other. Although anti-Kme antibodies were IgM only, a large proportion of the anti-Kme3 antibodies were switched to the IgG isotype. Mass spectrometric analysis showed that both of the antibodies were mainly derived from IGHV 3-7 and/or IGHV3-74 germ line genes with conserved CDR2. De novo sequencing showed that there was a mutation at either of the SS positions on the CDR1 region, which changed one of the serine residues to a basic amino acid, i.e., arginine or lysine. We also found that neither of the antibodies was expressed at birth, and their earliest appearance was approximately 5 months after birth. All healthy human beings expressed the antibodies when they reached age two and maintained the expression thereafter throughout their life. Patients with systemic lupus erythematosus had lower levels of the IgM isotype antibodies. Serum levels of the two IgM antibodies were closely correlated, implying that they were produced by cells from the same B cell subset. We also found that both anti-Kme and anti-Kme3 antibodies could bind and might take part in the clearance of neutrophil extracellular traps released from activated cells. In conclusion, although anti-Kme and anti-Kme3 antibodies share many similarities in their origins, they are different antibodies and have different characteristics.
authors.affiliation: Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing China.
authors.forename: Younan
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, The Netherlands.|Netherlands Proteomics Center, Utrecht, The Netherlands.
authors.forename: Fan
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Rheumatology and Immunoloy, the First Affiliated Hospital of Bengbu Medical College, Bengbu, China.
authors.forename: Linjie
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Nephrology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China.
authors.forename: Ruitong
authors.initials: R
authors.lastname: Gao
authors.affiliation: Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008239:Lysine / Q000032:analysis* / Q000276:immunology; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D012216:Rheumatic Diseases / Q000276:immunology; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008239:Lysine