Differential glycosylation of polyclonal IgG, IgG-Fc and IgG-Fab isolated from the sera of patients with ANCA-associated systemic vasculitis.
Post-translational modifications (PTMs) of proteins produced in vivo may be tissue, developmentally and/or disease specific. PTMs impact on the stability and function of proteins and offer a challenge to the commercial production of protein biotherapeutics. We have previously reported a marked deficit in galactosylation of oligosaccharides released from polyclonal IgG isolated from sera of patients with the anti-neutrophil cytoplasmic antibodies (ANCA) associated vasculitides; Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA). Whilst normal polyclonal IgG molecules are glycosylated within the IgG-Fc region, approximately 20% of molecules also bear oligosaccharides attached to the variable regions of the light or heavy chain IgG-Fab. It is of interest, therefore to compare profiles of oligosaccharides released from the IgG-Fc and IgG-Fab of normal IgG with that isolated from the sera of patients with WG or MPA. This study shows that whilst the oligosaccharides released from ANCA IgG-Fc are hypogalactosylated those released from IgG-Fab are galactosylated and sialylated. These results show that hypogalactosylation of IgG-Fc is not due to a defect in the glycosylation or processing machinery. It rather suggests a subtle change in IgG-Fc conformation that influences the addition of galactose. Remarkably, this influence is exerted on all plasma cells. Interestingly, a licensed monoclonal antibody therapeutic, produced in Sp2/0 cells, is also shown to be hypogalactosylated in its IgG-Fc but fully galactosylated in its IgG-Fab.
Holland
M
M
Division of Immunity and Infection, The Medical School, University of Birmingham, Edgbaston, UK.
Yagi
H
H
Takahashi
N
N
Kato
K
K
Savage
C O S
CO
Goodall
D M
DM
Jefferis
R
R
D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D016022:Case-Control Studies; D005690:Galactose; D006031:Glycosylation; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000097:blood / Q000737:chemistry; D007141:Immunoglobulin Fc Fragments / Q000097:blood / Q000737:chemistry; D007074:Immunoglobulin G / Q000097:blood / Q000737:chemistry*; D009844:Oligosaccharides / Q000032:analysis*; D011499:Protein Processing, Post-Translational; D014657:Vasculitis / Q000276:immunology*
D019268:Antibodies, Antineutrophil Cytoplasmic; D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D009844:Oligosaccharides; D005690:Galactose