Differential glycosylation of polyclonal IgG, IgG-Fc and IgG-Fab isolated from the sera of patients with ANCA-associated systemic vasculitis

Biochim Biophys Acta. 2006 Apr;1760(4):669-77. doi: 10.1016/j.bbagen.2005.11.021. Epub 2005 Dec 27.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Antineutrophil Cytoplasmic / blood*
  • Case-Control Studies
  • Galactose
  • Glycosylation
  • Humans
  • Immunoglobulin Fab Fragments / blood
  • Immunoglobulin Fab Fragments / chemistry
  • Immunoglobulin Fc Fragments / blood
  • Immunoglobulin Fc Fragments / chemistry
  • Immunoglobulin G / blood
  • Immunoglobulin G / chemistry*
  • Oligosaccharides / analysis*
  • Protein Processing, Post-Translational
  • Vasculitis / immunology*

Substances

  • Antibodies, Antineutrophil Cytoplasmic
  • Immunoglobulin Fab Fragments
  • Immunoglobulin Fc Fragments
  • Immunoglobulin G
  • Oligosaccharides
  • Galactose