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Characterization of THSD7A-antibodies not binding to glomerular THSD7A in a patient with diabetes mellitus but no membranous nephropathy.

ABSTRACT: Membranous nephropathy (MN) is an autoimmune disease caused by autoantibodies against the podocyte antigens phospholipase A₂ receptor 1 (PLA₂R1) and thrombospondin type 1 domain containing protein 7A (THSD7A) in 80% and 2-3% of patients, respectively. THSD7A antibodies are considered to be pathogenic and highly specific for MN patients. Using an indirect immunofluorescence test (IIFT) we detected THSD7A-antibodies (titre 1:10) in the serum of a patient with high proteinuria who, however, in the kidney biopsy was diagnosed with diabetic nephropathy and MN was excluded as a possible cause of proteinuria. Different immunofluorescence assays and Western blot techniques using recombinant THSD7A (rTHSD7A) or THSD7A from different human tissues revealed that the circulating THSD7A-autoantibodies were only of the IgG3 subclass. The patient serum reacted exclusively with rTHSD7A and only when the antigen was present in reducing Western blot conditions, or on formaldehyde-fixed cells for the IIFT. Our findings show for the first time the existence of circulating THSD7A-antibodies recognizing denatured/reduced rTHSD7A, which do not react with glomerular THSD7A in vivo and are thus presumptively non-pathogenic. As a consequence, kidney biopsy or Western blot analyses of THSD7A under non-reducing conditions should be performed to confirm the diagnosis of THSD7A-associated MN, especially in cases with low THSD7A-antibody levels in the IIFT.

SUBMITTER: Reinhard L

PROVIDER: S-EPMC8355258 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundMolecular characterization of nephropathies may facilitate pathophysiologic insight, development of targeted therapeutics, and transcriptome-based disease classification. Although membranous nephropathy (MN) is a common cause of adult-onset nephrotic syndrome, the molecular pathways of kidney damage in MN require further definition.MethodsWe applied a machine-learning framework to predict diagnosis on the basis of gene expression from the microdissected kidney tissue of participants in the Nephrotic Syndrome Study Network (NEPTUNE) cohort. We sought to identify differentially expressed genes between participants with MN versus those of other glomerulonephropathies across the NEPTUNE and European Renal cDNA Bank (ERCB) cohorts, to find MN-specific gene modules in a kidney-specific functional network, and to identify cell-type specificity of MN-specific genes using single-cell sequencing data from reference nephrectomy tissue.ResultsGlomerular gene expression alone accurately separated participants with MN from those with other nephrotic syndrome etiologies. The top predictive classifier genes from NEPTUNE participants were also differentially expressed in the ERCB participants with MN. We identified a signature of 158 genes that are significantly differentially expressed in MN across both cohorts, finding 120 of these in a validation cohort. This signature is enriched in targets of transcription factor NF-κB. Clustering these MN-specific genes in a kidney-specific functional network uncovered modules with functional enrichments, including in ion transport, cell projection morphogenesis, regulation of adhesion, and wounding response. Expression data from reference nephrectomy tissue indicated 43% of these genes are most highly expressed by podocytes.ConclusionsThese results suggest that, relative to other glomerulonephropathies, MN has a distinctive molecular signature that includes upregulation of many podocyte-expressed genes, provides a molecular snapshot of MN, and facilitates insight into MN's underlying pathophysiology.

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Characterization of THSD7A-antibodies not binding to glomerular THSD7A in a patient with diabetes mellitus but no membranous nephropathy.

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