TY - JOUR
T1 - Fc Galactosylation promotes hexamerization of human IgG1, leading to enhanced classical complement activation
AU - van Osch, Thijs L. J.
AU - Nouta, Jan
AU - Derksen, Ninotska I. L.
AU - van Mierlo, Gerard
AU - van der Schoot, C. Ellen
AU - Wuhrer, Manfred
AU - Rispens, Theo
AU - Vidarsson, Gestur
N1 - Funding Information: This work was supported by Stichting Sanquin Bloedvoorziening (PPO 17-44). Publisher Copyright: Copyright © 2021 by The American Association of Immunologists, Inc. All rights reserved.
PY - 2021/9/15
Y1 - 2021/9/15
N2 - Human IgG contains one evolutionarily conserved N-linked glycan in its Fc region at position 297. This glycan is crucial for Fc-mediated functions, including its induction of the classical complement cascade. This is induced after target recognition through the IgG-Fab regions, allowing neighboring IgG-Fc tails to associate through Fc:Fc interaction, ultimately leading to hexamer formation. This hexamerization seems crucial for IgG to enable efficient interaction with the globular heads of the first complement component C1q and subsequent complement activation. In this study, we show that galactose incorporated in the IgG1-Fc enhances C1q binding, C4, C3 deposition, and complement-dependent cellular cytotoxicity in human erythrocytes and Raji cells. IgG1-Fc sialylation slightly enhanced binding of C1q, but had little effect on downstream complement activation. Using various mutations that decrease or increase hexamerization capacity of IgG1, we show that IgG1-Fc galactosylation has no intrinsic effect on C1q binding to IgG1, but enhances IgG1 hexamerization potential and, thereby, complement activation. These data suggest that the therapeutic potential of Abs can be amplified without introducing immunogenic mutations, by relatively simple glycoengineering.
AB - Human IgG contains one evolutionarily conserved N-linked glycan in its Fc region at position 297. This glycan is crucial for Fc-mediated functions, including its induction of the classical complement cascade. This is induced after target recognition through the IgG-Fab regions, allowing neighboring IgG-Fc tails to associate through Fc:Fc interaction, ultimately leading to hexamer formation. This hexamerization seems crucial for IgG to enable efficient interaction with the globular heads of the first complement component C1q and subsequent complement activation. In this study, we show that galactose incorporated in the IgG1-Fc enhances C1q binding, C4, C3 deposition, and complement-dependent cellular cytotoxicity in human erythrocytes and Raji cells. IgG1-Fc sialylation slightly enhanced binding of C1q, but had little effect on downstream complement activation. Using various mutations that decrease or increase hexamerization capacity of IgG1, we show that IgG1-Fc galactosylation has no intrinsic effect on C1q binding to IgG1, but enhances IgG1 hexamerization potential and, thereby, complement activation. These data suggest that the therapeutic potential of Abs can be amplified without introducing immunogenic mutations, by relatively simple glycoengineering.
UR - http://www.scopus.com/inward/record.url?scp=85114594319&partnerID=8YFLogxK
U2 - https://doi.org/10.4049/jimmunol.2100399
DO - https://doi.org/10.4049/jimmunol.2100399
M3 - Article
C2 - 34408013
SN - 0022-1767
VL - 207
SP - 1545
EP - 1554
JO - Journal of immunology (Baltimore, Md.
JF - Journal of immunology (Baltimore, Md.
IS - 6
ER -