title: Human IgG2 antibodies display disulfide-mediated structural isoforms.
abstract: In this work, we present studies of the covalent structure of human IgG2 molecules. Detailed analysis showed that recombinant human IgG2 monoclonal antibody could be partially resolved into structurally distinct forms caused by multiple disulfide bond structures. In addition to the presently accepted structure for the human IgG2 subclass, we also found major structures that differ from those documented in the current literature. These novel structural isoforms are defined by the light chain constant domain (C(L)) and the heavy chain C(H)1 domain covalently linked via disulfide bonds to the hinge region of the molecule. Our results demonstrate the presence of three main types of structures within the human IgG2 subclass, and we have named these structures IgG2-A, -B, and -A/B. IgG2-A is the known classic structure for the IgG2 subclass defined by structurally independent Fab domains and hinge region. IgG2-B is a structure defined by a symmetrical arrangement of a (C(H)1-C(L)-hinge)(2) complex with both Fab regions covalently linked to the hinge. IgG2-A/B represents an intermediate form, defined by an asymmetrical arrangement involving one Fab arm covalently linked to the hinge through disulfide bonds. The newly discovered structural isoforms are present in native human IgG2 antibodies isolated from myeloma plasma and from normal serum. Furthermore, the isoforms are present in native human IgG2 with either kappa or lambda light chains, although the ratios differ between the light chain classes. These findings indicate that disulfide structural heterogeneity is a naturally occurring feature of antibodies belonging to the human IgG2 subclass.
authors.affiliation: Department of Analytical Sciences, Amgen Inc., Thousand Oaks, California 91320, USA. jwypych@amgen.com
authors.forename: Jette
authors.initials: J
authors.lastname: Wypych
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Amy
authors.initials: A
authors.lastname: Guo
authors.forename: Zhongqi
authors.initials: Z
authors.lastname: Zhang
authors.forename: Theresa
authors.initials: T
authors.lastname: Martinez
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Allen
authors.forename: Szilan
authors.initials: S
authors.lastname: Fodor
authors.forename: Drew N
authors.initials: DN
authors.lastname: Kelner
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Flynn
authors.forename: Yaoqing Diana
authors.initials: YD
authors.lastname: Liu
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Bondarenko
authors.forename: Margaret Speed
authors.initials: MS
authors.lastname: Ricci
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Dillon
authors.forename: Alain
authors.initials: A
authors.lastname: Balland
mesh_terms: D004220:Disulfides / Q000737:chemistry*; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry* / Q000235:genetics; D007145:Immunoglobulin kappa-Chains / Q000737:chemistry* / Q000235:genetics; D007146:Immunoglobulin lambda-Chains / Q000737:chemistry* / Q000235:genetics; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D020836:Protein Structure, Quaternary / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D004220:Disulfides; D007074:Immunoglobulin G; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D020033:Protein Isoforms; D011994:Recombinant Proteins