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Biochim Biophys Acta. 2006 Apr;1760(4):669-77. Epub 2005 Dec 27.

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

Author information

1
Division of Immunity and Infection, The Medical School, University of Birmingham, Edgbaston, UK.

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.

PMID:
16413679
DOI:
10.1016/j.bbagen.2005.11.021
[Indexed for MEDLINE]

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