Variable domain N-linked glycosylation and negative surface charge are key features of monoclonal ACPA: Implications for B-cell selection

Eur J Immunol. 2018 Jun;48(6):1030-1045. doi: 10.1002/eji.201747446. Epub 2018 Apr 6.


Autoreactive B cells have a central role in the pathogenesis of rheumatoid arthritis (RA), and recent findings have proposed that anti-citrullinated protein autoantibodies (ACPA) may be directly pathogenic. Herein, we demonstrate the frequency of variable-region glycosylation in single-cell cloned mAbs. A total of 14 ACPA mAbs were evaluated for predicted N-linked glycosylation motifs in silico, and compared to 452 highly-mutated mAbs from RA patients and controls. Variable region N-linked motifs (N-X-S/T) were strikingly prevalent within ACPA (100%) compared to somatically hypermutated (SHM) RA bone marrow plasma cells (21%), and synovial plasma cells from seropositive (39%) and seronegative RA (7%). When normalized for SHM, ACPA still had significantly higher frequency of N-linked motifs compared to all studied mAbs including highly mutated HIV broadly-neutralizing and malaria-associated mAbs. The Fab glycans of ACPA-mAbs were highly sialylated, contributed to altered charge, but did not influence antigen binding. The analysis revealed evidence of unusual B-cell selection pressure and SHM-mediated decrease in surface charge and isoelectric point in ACPA. It is still unknown how these distinct features of anti-citrulline immunity may have an impact on pathogenesis. However, it is evident that they offer selective advantages for ACPA+ B cells, possibly through non-antigen driven mechanisms.

Keywords: Anti-CCP; Anti-citrullinated protein autoantibodies; Autoreactive B cells; Fab glycosylation; N-linked glycosylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs / genetics
  • Anti-Citrullinated Protein Antibodies / genetics
  • Anti-Citrullinated Protein Antibodies / metabolism*
  • Antibodies, Monoclonal / genetics
  • Antibodies, Monoclonal / metabolism*
  • Arthritis, Rheumatoid / immunology*
  • B-Lymphocytes / immunology*
  • Cell Differentiation
  • Cells, Cultured
  • Clone Cells
  • Computational Biology
  • Glycosylation
  • Humans
  • Immunoglobulin Variable Region / genetics
  • Immunoglobulin Variable Region / metabolism*
  • Lymphocyte Activation
  • Synovial Fluid / immunology


  • Anti-Citrullinated Protein Antibodies
  • Antibodies, Monoclonal
  • Immunoglobulin Variable Region