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Abstract: FR-OR34

Semaphorin 3B-Associated Membranous Nephropathy

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Sethi, Sanjeev, Mayo Clinic, Rochester, Minnesota, United States
  • Debiec, Hanna, Sorbonne Universite, Paris, Île-de-France, France
  • Madden, Benjamin J., Mayo Clinic, Rochester, Minnesota, United States
  • Vivarelli, Marina, Ospedale Pediatrico Bambino Gesu, Roma, Lazio, Italy
  • Charlesworth, Cristine, Mayo Clinic, Rochester, Minnesota, United States
  • Ravindran, Aishwarya, Mayo Clinic, Rochester, Minnesota, United States
  • Gross, Louann, Mayo Clinic, Rochester, Minnesota, United States
  • Buob, David, Sorbonne Universite, Paris, France
  • Tran, Cheryl L., Mayo Clinic, Rochester, Minnesota, United States
  • Emma, Francesco, Ospedale Pediatrico Bambino Gesu, Roma, Lazio, Italy
  • Diomedi-Camassei, Francesca, Ospedale Pediatrico Bambino Gesu, Roma, Lazio, Italy
  • Fervenza, Fernando C., Mayo Clinic, Rochester, Minnesota, United States
  • Ronco, Pierre M., Sorbonne Universite, Paris, France
Background

Membranous nephropathy (MN) results from subepithelial antigen-antibody complex deposition along the glomerular basement membrane (GBM). Although PLA2R, THSD7A, and NELL-1 account for a majority (approximately 80%) of the target antigens, the target antigen in the remaining MN is not known.

Methods

We performed laser microdissection and mass spectrometry (MS) of glomeruli in kidney biopsies of 70 cases of PLA2R-negative MN. We detected high spectral counts of a unique protein Semaphorin 3B (Sema3B) in 3 cases. Immunohistochemistry (IHC) for Sema3B was then performed to confirm MS results. Next, we analyzed 3 validation cohorts (2 French and 1 Italian) of 118 PLA2R-negative MN cases by immunofluorescence microscopy (IF). Confocal microscopy studies were done to confirm colocalization of IgG and Sema3B along the GBM. Next, serum antibodies were detected by Western blotting (WB).

Results

MS identified a unique protein, Sema3B in 3 cases of PLA2R-negative MN. MS failed to detect Sema3B in the remaining 67 PLA2R-negative MN, in 23 PLA2R-associated MN, and 88 controls that included IgA nephropathy, diabetes, FSGS and minimal change disease. Semaphorin 3B in all 3 positive cases localized as granular deposits along the GBM by IHC (Figure 1). Next, an additional 8 cases of Sema3B-associated MN were identified in 3 validation cohorts by IF. Confocal microscopy showed that both IgG and Sema3B co-localized to the GBM. In 4 of 11 cases, kidney biopsy also showed tubular basement membrane (TBM) IgG deposits, the TBM deposits were negative for Sema3B. WB analysis in 5 available sera showed reactivity to reduced Sema3B in 4 of 4 patients with active disease and no reactivity in 1 patient in clinical remission; there was also no reactivity in control sera. Eight (73%) of the 11 cases of Semaphorin 3B-associated MN were pediatric cases. In 5 of the 8 children, the disease started below the age of 2 years.

Conclusion

Semaphorin 3B-associated MN is a distinct type of MN, and is predominantly present in pediatric patients.

Figure 1 shows bright granular capillary wall staining for Sema3B in 3 cases of Sema3B-associated MN.