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Anti phospholiapse a2 receptor

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"anti-PLA2R" AND "membranous nephropathy"

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membranous nephropathy PLA2R immunofluorescence subepithelial deposits

This composite of confocal light microscopy images illustrates immunofluorescence staining patterns in human glomerular tissue, specifically focusing on membranous nephropathy (MN). The 20-panel figure is organized into five rows (A-T), each representing a different IgG target: total IgG, IgG1, IgG2, IgG3, and IgG4. Within each row, four panels show: (1) DAPI nuclear staining in blue, (2) IgG or specific IgG subclasses in green, (3) PLA2R antigen in red, and (4) a merged overlay. The staining reveals a granular, loop-like distribution along the glomerular basement membrane (GBM), characteristic of subepithelial immune complex deposits. In the merged columns (D, H, L, P, T), the overlap of green (IgG) and red (PLA2R) signals produces a yellow color, demonstrating the co-localization of the PLA2R antigen with total IgG and all four IgG subclasses. DAPI staining confirms that these deposits are extracellular and distinct from cellular nuclei. This visual evidence supports the role of PLA2R as a major autoantigen in primary MN and characterizes the subclass composition of the associated immune deposits.

This composite of confocal light microscopy images illustrates immunofluorescence staining patterns in human glomerular tissue, specifically focusing on membranous nephropathy (MN). The 20-panel figure is organized into five rows (A-T), each representing a different IgG target: total IgG, IgG1, IgG2, IgG3, and IgG4. Within each row, four panels show: (1) DAPI nuclear staining in blue, (2) IgG or specific IgG subclasses in green, (3) PLA2R antigen in red, and (4) a merged overlay. The staining reveals a granular, loop-like distribution along the glomerular basement membrane (GBM), characteristic of subepithelial immune complex deposits. In the merged columns (D, H, L, P, T), the overlap of green (IgG) and red (PLA2R) signals produces a yellow color, demonstrating the co-localization of the PLA2R antigen with total IgG and all four IgG subclasses. DAPI staining confirms that these deposits are extracellular and distinct from cellular nuclei. This visual evidence supports the role of PLA2R as a major autoantigen in primary MN and characterizes the subclass composition of the associated immune deposits.

This diagnostic image is a high-power (400x) immunofluorescence micrograph of a human glomerulus from a renal biopsy specimen. The image demonstrates a diffuse, granular staining pattern of 3+ intensity, specifically localized along the glomerular capillary loops. The green fluorescent signal highlights the convoluted, interconnected morphology of the basement membrane area in a 'beaded' fashion, which is characteristic of immune complex deposition. Pathologically, this visual finding represents positive staining for phospholipase A2 receptor (PLA2R) antibodies, a definitive diagnostic marker for primary membranous nephropathy. The absence of mesangial or endocapillary staining emphasizes the subepithelial nature of the deposits. This specimen is critical for differentiating primary autoimmune-mediated glomerular disease from secondary causes in patients presenting with nephrotic syndrome.

This diagnostic image is a high-power (400x) immunofluorescence micrograph of a human glomerulus from a renal biopsy specimen. The image demonstrates a diffuse, granular staining pattern of 3+ intensity, specifically localized along the glomerular capillary loops. The green fluorescent signal highlights the convoluted, interconnected morphology of the basement membrane area in a 'beaded' fashion, which is characteristic of immune complex deposition. Pathologically, this visual finding represents positive staining for phospholipase A2 receptor (PLA2R) antibodies, a definitive diagnostic marker for primary membranous nephropathy. The absence of mesangial or endocapillary staining emphasizes the subepithelial nature of the deposits. This specimen is critical for differentiating primary autoimmune-mediated glomerular disease from secondary causes in patients presenting with nephrotic syndrome.

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Anti-Phospholipase A2 Receptor (anti-PLA2R) Antibody

What it is

PLA2R is a transmembrane receptor on podocytes. It is the major target antigen in primary (idiopathic) membranous nephropathy (MN). The antibody is an IgG autoantibody, predominantly IgG4. It binds PLA2R on the podocyte surface and forms subepithelial immune deposits. These activate complement and injure the podocyte, which causes proteinuria.
Structure of the antigen. PLA2R has 10 extracellular domains: an N-terminal cysteine-rich domain (CysR), one fibronectin type II domain and eight C-type lectin-like domains (CTLD). Autoantibodies target at least four regions: CysR, CTLD1, CTLD7 and CTLD8. CysR contains a 31-amino-acid immunodominant epitope that every anti-PLA2R-positive patient recognizes. - Comprehensive Clinical Nephrology, 7th Edition, p. 299 (Fig. 21.3)
PLA2R structural diagram

Genetics

Risk variants lie in PLA2R1 and in HLA class II (the peptide-binding groove). Variants in IRF4 and NFKB1 have also been reported. An external trigger such as an environmental pollutant may set off disease in genetically predisposed people. - Comprehensive Clinical Nephrology, 7th Edition, p. 298-299

Clinical use

1. Diagnosis
  • Serum anti-PLA2R is positive in about 75-80% of primary MN.
  • Complement levels, ANA, ANCA and RF are normal.
  • A positive serum test in a nephrotic patient with no secondary cause can support a diagnosis of primary MN without a biopsy. This depends on context, for example preserved kidney function and no features of secondary disease.
  • A negative test does not exclude MN. Other antigens include THSD7A, NELL1 and EXT1/2 (the last two are usually associated with secondary MN). - Robbins, Cotran & Kumar Pathologic Basis of Disease (antigen list in the glomerular injury figure)
2. Prognosis
  • A higher titer at diagnosis (highest tertile) is associated with loss of kidney function.
  • Epitope spreading, meaning antibodies beyond the N-terminal epitope, has been linked to a worse outcome in some studies but not others.
  • Antibodies to intracellular antigens may carry an independent adverse risk.
  • A low or falling titer predicts spontaneous or treatment-induced complete remission. - Comprehensive Clinical Nephrology, 7th Edition, p. 303-304 (Table 21.4)
3. Monitoring and treatment decisions
  • Antibody levels change before proteinuria and albumin do. A falling titer typically comes first, and clinical remission follows after a lag. This lag reflects the time needed to stop forming deposits and let the podocyte recover.
  • A high or rising titer suggests the disease will persist or worsen.
  • The textbook states the titer should not be used alone to start or delay immunosuppression. Albumin, proteinuria and eGFR must also be considered.
  • Immunologic remission (undetectable titer) helps guide when to reduce or stop treatment.
  • The same textbook gives relapse rates after complete remission of about 25-40%, and up to 50% after partial remission.
4. Kidney transplant Persistent or high pre-transplant titers are a risk factor for recurrent MN in the graft.

Pathology correlate

Biopsy shows granular IgG (mainly IgG4) along the capillary loops by immunofluorescence. This co-localizes with PLA2R staining. Electron microscopy shows subepithelial deposits. Silver stain shows GBM "spikes." - Comprehensive Clinical Nephrology, 7th Edition, p. 299-300
PLA2R co-localizing with IgG subclasses in MN
Granular PLA2R staining 3+ along capillary loops

Testing notes

Assays include ELISA and indirect immunofluorescence (cell-based assay). ELISA is quantitative and is the usual choice for follow-up. Cell-based assays are more sensitive at low titers. Titers can fall quickly after anti-CD20 therapy (rituximab, obinutuzumab). I did not look up assay sensitivity figures or treatment thresholds, so check your local laboratory and guidelines (KDIGO) for those.

Recent evidence (last 2 years)

These recent reviews do not contradict the textbook. They expand on it:
If you meant something specific, such as exam points, treatment protocols or assay interpretation, tell me and I'll go deeper.
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