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Abstract: TH-PO452

Minor Antigens in Membranous Nephropathy Identified by Mass Spectrometry

Session Information

Category: Glomerular Diseases

  • 1302 Glomerular Diseases: Immunology and Inflammation

Authors

  • Caza, Tiffany, Arkana Laboratories, Little Rock, Arkansas, United States
  • Hassen, Samar, Arkana Laboratories, Little Rock, Arkansas, United States
  • Herzog, Christian, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Storey, Aaron J., University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Edmondson, Ricky, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Arthur, John M., University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Kenan, Daniel J., Arkana Laboratories, Little Rock, Arkansas, United States
  • Larsen, Christopher Patrick, Arkana Laboratories, Little Rock, Arkansas, United States
Background

Multiple autoantigens have been identified in membranous nephropathy (MN) by tissue-based proteomics. However, the antigenic targets of disease are unknown for >10% of MN and >50% of cases of membranous lupus nephritis. We identified multiple new targets in PLA2R-/THSD7A-/EXT-/NELL1-quadruple negative MN biopsies through mass spectrometry (MS) of immune complexes recovered from biopsy tissue of patients with MN.

Methods

MN cases negative for PLA2R, THSD7A, EXT1/2, and NELL1 were identified from a biopsy database. Protein G immunoprecipitation was used to recover immune complexes from frozen kidney biopsy tissue, followed by interrogation by mass spectrometry (MS). Potential antigens were confirmed through paraffin immunofluorescence of protein targets, followed by co-localization of the candidate protein with IgG within immune deposits. A consecutive series of 81 PLA2R-negative MN biopsies was screened to determine the frequency for each of the protein targets in MN.

Results

Seven novel antigenic targets were identified within isolated immune complexes from MN biopsies by MS, including FCN3, CD206, EEA1, SEZ6L1, NPR3, MSP1, and VASN. Peptides from these proteins were not enriched in PLA2R (n=47), THSD7A (n=49), NELL1 (n=54), or EXT1/2 (n=51) control cases. Between 3-30 unique peptides were detected for each novel antigen. Separate from the index cases, a series of 81 PLA2R-negative MN cases were screened for each antigen by paraffin immunofluorescence. Frequencies were FCN3 (1/81), CD206 (1/81), EEA1 (5/81), SEZ6L1 (1/81), MSP1 (2/81), and VASN (7/81). No additional cases of NPR3 were identified in screening (likely <1% of cases). All cases showed co-localization of IgG within glomerular immune deposits.

Conclusion

Seven novel protein targets were identified in MN, each having a low frequency of overall cases. Further work is required to examine for circulating antibodies and to determine whether unique histopathologic characteristics or disease associations exist.

Funding

  • NIDDK Support