title: Isotype-specific glycosylation analysis of mouse IgG by LC-MS.
abstract: With mice being the top model organism in immunology and with Fc glycosylation being increasingly recognized as important modulator of antibody function, the time has come to take a look at the glycosylation of mouse IgG isotypes. Tryptic glycopeptides of mouse IgG1, IgG2, and IgG3 differ in mass and so these three isoforms can be easily discriminated by MS. Commercial IgG contained a rare IgG1 variant but no IgG3, which, however, was found in sera of C57BL/6 and BALB/c mice. These strains deviated with regard to IgG2a and IgG2b alleles. The Ig2a B allele was not observed in any of the four samples investigated. All a/c isotypes contain the same glycopeptide sequence, which deviates from that of IgG2b by containing Leu instead of Ile. The Leu/Ile glycopeptide variants were separated by RP chromatography and the order of elution was determined. The major glycoforms on all isotypes were fucosylated with no and one galactose (GnGnF and GnAF) followed by fully galactosylated AAF and smaller amounts of mono- and disialylated N-glycans. In the commercial serum pool, the relative ratios of glycans differed between isotypes. Sialic acid exclusively occurred as N-glycolylneuraminic acid. Fucosylation was essentially complete. No bisected and no α1,3-galactosylated glycans were found.
authors.affiliation: Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Maresch
authors.affiliation: Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Altmann
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D006031:Glycosylation; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry* / Q000302:isolation & purification; D007074:Immunoglobulin G / Q000097:blood / Q000737:chemistry*; D007132:Immunoglobulin Isotypes / Q000097:blood / Q000737:chemistry* / Q000145:classification; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019158:N-Acetylneuraminic Acid / Q000737:chemistry / Q000302:isolation & purification; D009438:Neuraminic Acids / Q000737:chemistry / Q000302:isolation & purification; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D011134:Polysaccharides / Q000737:chemistry / Q000302:isolation & purification; D016415:Sequence Alignment; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D009438:Neuraminic Acids; D010455:Peptides; D011134:Polysaccharides; C032592:N-glycolylneuraminic acid; D019158:N-Acetylneuraminic Acid
keywords: Glycoproteomics; Ig; IgG isotype; Mouse IgG; N-glycolylneuraminic acid