Precipitating anti-dsDNA peptide repertoires in lupus
J J Wang1, A D Colella1, D Beroukas1
1Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, SA, Australia.
Clinical and Experimental Immunology
|August 8, 2018
Summary
Researchers analyzed anti-double-stranded (ds)DNA autoantibodies in systemic lupus erythematosus (SLE) using a novel proteomic method. They discovered shared immunoglobulin variable (IgV) region features and extensive mutations, revealing insights into high-affinity antibody responses.
Area of Science:
- Immunology
- Proteomics
- Autoimmunity
Background:
- Anti-double-stranded (ds)DNA autoantibodies are key biomarkers for systemic lupus erythematosus (SLE).
- The immunoglobulin variable (IgV) region composition of these antibodies in the serum proteome remains largely uncharacterized.
- Understanding IgV region composition is crucial for elucidating the mechanisms of high-affinity autoantibody production.
Purpose of the Study:
- To investigate the IgV subfamily expression and mutational signatures of precipitating anti-dsDNA autoantibodies.
- To characterize the proteomic composition of serum anti-dsDNA responses in SLE patients.
- To explore the role of specific mutations in the affinity and specificity of anti-dsDNA antibodies.
Main Methods:
- A novel proteomic workflow utilizing de novo mass spectrometric sequencing of anti-dsDNA precipitins.
- Analysis of IgV peptide maps from eight SLE subjects.
- Quantitative multiple reaction monitoring (MRM) to track clonal L-chain CDR3 peptide expression levels.
Main Results:
- Serum anti-dsDNA proteomes were oligoclonal, exhibiting shared (public) expression of IgG heavy and kappa light chain variable region subfamilies.
- Extensive public and private amino acid replacement mutations, notably arginine substitutions, were identified in IgV peptide maps.
- Shared L-chain complementarity determining region 3 (CDR3) peptides with arginine substitutions, particularly from the IGKV3-20 subfamily, were sequenced.
- Changes in a specific clonal L-chain CDR3 peptide paralleled anti-dsDNA antibody levels, as measured by Farr radioimmunoassays (RIA).
Conclusions:
- The heavily mutated IgV peptide signatures indicate strong selective pressures shaping humoral anti-dsDNA responses in germinal centers.
- The novel proteomic approach, involving direct sequencing of precipitins, streamlines antibody sequencing and is applicable to other precipitating serum antibodies.
- This study provides significant insights into the molecular composition and evolution of high-affinity anti-dsDNA autoantibodies in SLE.
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