Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


Dynamic Evolution of a Public Clonotypic Autoantibody Specific for Ro60: Perpetuating Humoral Autoimmunity Through Clonotypic Shift.

Lindop1,  Rhianna, Arentz1,  Georgia, Tim,  , Chataway2,  K., Thurgood1,  Lauren A., Jackson1,  Michael W., Gordon1,  Tom P.

Flinders Medical Centre and Flinders University, Adelaide, Australia
Flinders University, Adelaide, Australia

Background/Purpose:

We have recently discovered a public Ro60-reactive clonotypic autoantibody specified by a unique VH3–23/VK3–20 chain pairing, by using positive epitope selection of human sera with anti-Ro/La responses and de novo sequencing of the purified autoantibody proteome (Lindop et al, Arthritis Rheum, in press). In the present longitudinal study, we use this unique clonotypic signature to trace the evolution of humoral autoimmunity directed against a member of the ENA family in human systemic autoimmunity.

Methods:

Clonotypic VH3–23/VK3–20 IgGs specific for the immunodominant Ro60peg determinant (amino acids 193–236) were purified by epitope-specific affinity chromatography from serial serum samples of 5 patients with primary Sjögren's syndrome (ranges from 1 to 10 years apart). Direct variable (V)-region sequencing of heavy and light chains was performed by high-resolution de novo orbitrap mass spectrometric sequencing. Relative anti-Ro60peg binding affinities were compared by the KCSN elution method.

Results:

Patient sera tested at each time point expressed a dominant Ro60peg-specific monoclonal IgG1 kappa species with a characteristic VH3–23/VK3–20 gene rearrangement signature, consistent with a common clonal origin for each patient. However, near full-length protein sequencing of serial samples from individual patients revealed that each clonotypic autoantibody, irrespective of the duration of disease, was subtly different from its predecessor, being specified by a unique pattern of somatic V-region mutations. Relative affinities of anti-Ro60peg clonotypic autoantibody variants were remarkably constant over years and even decades in the face of ongoing clonotypic shift, explained by preservation of key amino acid replacement mutations in the CDR regions critical for antibody binding.

Conclusion:

Analysis of the autoantibody proteome has demonstrated for the first time a dynamic process of clonal evolution in systemic humoral autoimmunity, characterised by serial replacement of existing clonotypes with somatically mutated variants that presumably have a survival advantage over their predecessors. The selection pressures driving this process are not based solely on affinity for the autoepitope since the response reaches an affinity ceiling early in disease. The perpetual clonotypic shifts allow this secreted autoantibody to keep one step ahead of B-cell tolerogenic censuring mechanisms, resulting in life-long production of potentially pathogenic anti-Ro60 autoantibodies in patients with lupus and primary Sjögren's syndrome.

To cite this abstract, please use the following information:
Lindop, Rhianna, Arentz, Georgia, Tim, , Chataway, K., Thurgood, Lauren A., Jackson, Michael W., et al; Dynamic Evolution of a Public Clonotypic Autoantibody Specific for Ro60: Perpetuating Humoral Autoimmunity Through Clonotypic Shift. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1751
DOI:

Abstract Supplement

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