Membranous Nephropathy with Lambda Light Chain Restriction: A Rare Form with Serum Negative and Tissue Positive PLA2R Ab

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults. Subepithelial polyclonal immunoglobulin deposits and >70% M-type phospholipase A2 receptor antibody positivity are typical findings in idiopathic MN. A 58-year-old female patient was admitted with clinical presentation of nephrotic syndrome. Autoimmune diseases, infections, and malignancies were ruled out after clinical and laboratory evaluations. Diagnostic work-up revealed serum PLA2R antibody negativity and diffuse thickening of glomerular capillary wall on biopsy, while glomerular capillary wall IgG, C3, and Lambda monotypic light chain deposition and PLA2R1 positivity were detected by immunofluorescence and immunohistochemical examination, respectively. Following prednisolone treatment, creatinine and proteinuria were markedly regressed. The MN cases with a light chain deposits are rare and experience regarding their treatment are insufficient.

An Investigation of the Antigenic Characteristics of the Renal Glomerulus in the Rat

<p>The finding of a granular deposition of immunoglobulin in the kidney in experimental animal models of glomerulonephritis has been been interpreted as resulting from the random deposition of immune complexes in the glomeruli. Recent data suggests that although immune complex deposition may be an important factor in some forms of glomerulonephritis, the in situ formation of immune complexes between circulating anti-kidney antibodies and fixed glomerular capillary wall antigens may also be a significant factor in the pathogenesis of some animal models of glomerulonephritis. To examine the characteristics of discontinuously represented glomerular capillary wall antigens in the rat, monoclonal antibodies were generated against a glomerular plasma membrane fraction, depleted of glomerular basement membrane, prepared from isolated Lewis rat glomeruli. A total of 17 hybridomas, generated from the fusion of splenocytes obtained from mice immunised with the glomerular membrane fraction produced monoclonal antibodies which reacted with discontinuously represented antigens in the glomerulus and renal tubules. One further hybridoma secreted a monoclonal antibody which reacted with an antigen present on glomerular and tubular nuclear membranes. No hybridomas were produced which secreted a monoclonal antibody which reacted with linearly arrayed glomerular basement membrane antigens. Two of these monoclonal antibodies, both of the IgM subclass and code-named PH7 and SC5, produced a heavy granular glomerular staining pattern when examined by indirect immunofluorescence microscopy. Neither monoclonal antibody was kidney specific, with reactivity being demonstrated with a number of non-renal tissues. When administered intravenously to normal Lewis rats both SC5 and PH7 induced a mild proteinuric lesion. The proteinuria was not associated with histopathological changes at the light or electron microscope level. Immunoblotting experiments revealed that SC5 reacted predominantly with a protein band of 96 kDa present in detergent extracts of isolated glomeruli and glomerular plasma membranes. PH7 was shown to react with three low molecular weight proteins of 14, 13 and 11 kDa The findings of this study demonstrate the potential for a nephritogenic response to occur following the in situ formation of immune complexes between circulating anti-kidney antibodies and discontinuously arrayed non-glomerular, basement membrane glomerular capillary wall antigens characterised by granular immunofluorescence patterns,in animal models of glomerulonephritis.</p>

An Investigation of the Antigenic Characteristics of the Renal Glomerulus in the Rat

<p>The finding of a granular deposition of immunoglobulin in the kidney in experimental animal models of glomerulonephritis has been been interpreted as resulting from the random deposition of immune complexes in the glomeruli. Recent data suggests that although immune complex deposition may be an important factor in some forms of glomerulonephritis, the in situ formation of immune complexes between circulating anti-kidney antibodies and fixed glomerular capillary wall antigens may also be a significant factor in the pathogenesis of some animal models of glomerulonephritis. To examine the characteristics of discontinuously represented glomerular capillary wall antigens in the rat, monoclonal antibodies were generated against a glomerular plasma membrane fraction, depleted of glomerular basement membrane, prepared from isolated Lewis rat glomeruli. A total of 17 hybridomas, generated from the fusion of splenocytes obtained from mice immunised with the glomerular membrane fraction produced monoclonal antibodies which reacted with discontinuously represented antigens in the glomerulus and renal tubules. One further hybridoma secreted a monoclonal antibody which reacted with an antigen present on glomerular and tubular nuclear membranes. No hybridomas were produced which secreted a monoclonal antibody which reacted with linearly arrayed glomerular basement membrane antigens. Two of these monoclonal antibodies, both of the IgM subclass and code-named PH7 and SC5, produced a heavy granular glomerular staining pattern when examined by indirect immunofluorescence microscopy. Neither monoclonal antibody was kidney specific, with reactivity being demonstrated with a number of non-renal tissues. When administered intravenously to normal Lewis rats both SC5 and PH7 induced a mild proteinuric lesion. The proteinuria was not associated with histopathological changes at the light or electron microscope level. Immunoblotting experiments revealed that SC5 reacted predominantly with a protein band of 96 kDa present in detergent extracts of isolated glomeruli and glomerular plasma membranes. PH7 was shown to react with three low molecular weight proteins of 14, 13 and 11 kDa The findings of this study demonstrate the potential for a nephritogenic response to occur following the in situ formation of immune complexes between circulating anti-kidney antibodies and discontinuously arrayed non-glomerular, basement membrane glomerular capillary wall antigens characterised by granular immunofluorescence patterns,in animal models of glomerulonephritis.</p>

Synaptopodin deficiency exacerbates kidney disease in a mouse model of Alport Syndrome

Synaptopodin (Synpo) is an actin-associated protein in podocyte foot processes. By generating mice that completely lack Synpo, we previously showed that Synpo is dispensable for normal kidney function. However, the lack of Synpo worsened Adriamycin nephropathy, indicating a protective role for Synpo in injured podocytes. Here we investigated whether the lack of Synpo directly impacts a genetic disease, Alport syndrome (AS), because Synpo is reduced in the podocytes of affected humans and mice; whether this is merely an association or pathogenic is unknown. We used Col4a5 mutant mice that model X-linked AS, showing glomerular basement membrane (GBM) abnormalities, eventual foot process effacement, and progression to ESKD. We intercrossed mice carrying mutations in Synpo and Col4a5 to produce doubly mutant mice. Urine and tissue were taken at select time points to evaluate albuminuria, histopathology, and glomerular capillary wall composition and ultrastructure. The lack of Synpo in Col4a5-/Y, Col4a5-/-, or Col4a5+/- Alport mice led to acceleration of disease progression, including more severe proteinuria and glomerulosclerosis. The absence of Synpo attenuated the shift of myosin IIA from the podocyte cell body and major processes to the actin cables near the GBM in the areas of effacement. We speculate that this is mechanistically associated with enhanced loss of podocytes due to easier detachment from the GBM. We conclude that Synpo deletion exacerbates the disease phenotype in Alport mice, revealing the podocyte actin cytoskeleton as a target for therapy in patients with AS.

The Efficacy of Rituximab in the Treatment of Membranous Nephropathy

Rituximab is a chimeric monoclonal antibody directed against the CD20 expressed on B cells, originally used to treat lymphoma but is increasingly used for the treatment of autoimmune diseases. Membranous nephropathy is an autoimmune disease resulting from the deposition of IgG and complements components onto the subepithelial layer of the glomerular capillary wall and remains the leading cause of nephrotic syndrome in adults. Several prospective and retrospective studies showed rituximab induces remission and may decrease proteinuria in patients with membranous nephropathy. Considerable evidence supports the use of B-cell depletion as initial therapy in nephrotic patients with membranous nephropathy. This review focuses on the efficacy and safety of rituximab in the treatment of membranous nephropathy.Keywords: Membranous nephropathy; rituximab; treatment

P0293FRACTIONAL EXCRETION OF TOTAL PROTEIN IS AN ACCURATE INDICATOR OF PROTEINURIA IN NPHROTIC PATIENTS

Background and Aims Urinary total protein/creatinine ratio (U-TP/Cr) is a simple and useful indicator of proteinuria. And it had been shown to correlate well with 24-hour urinary protein test (24hr UPT). However, U-TP/Cr is not always accurately reflecting the degree of proteinuria, especially in cases with heavy proteinuria. Proteinuria in nephrotic syndrome could be defined as the result of changed sieving coefficient (SC) of plasma total protein through the glomerular capillary wall. Therefore, we studied fractional excretion of total protein (FETP; total protein clearance/creatinine clearance %) instead of directly unmeasurable SC. The accuracy of the FETP was verified by 24hr UPT in comparison with U-TP/Cr. Method Sixty-three serum and urine samples were collected from 35 pediatric patients with various age (age: 3 − 20 y; mean: 10.3 y, 22 male, 13 female) with hypoproteinemia (TP≦ 5.0 mg/dL), heavy proteinuria (FETP≧ 0.01%), and normal GFR (creatinine clearance ≧ 100 ml/min). The correlations between 24hrUPT and U-P/Cr and FETP were studied using samples obtained the same time and the superiority was statistically examined. Results Mean±SE of 24hUPT, U-TP/Cr and FETP (%) were 5.53±0.71 (g/day), 10.23±1.26 (g/gCr), and 0.12±0.016 (%) respectively. R values for the correlation between 24hrUPT and U-TP/Cr and 24hr UPT and FETP were 0.64 and 0.86 respectively. FETP showed a statistically better correlation with 24hrUPT than with U-TP/Cr (P: 0.0001). Conclusion FETP is an accurate indicator of 24hr UPT for nephrotic patients under conditions of heavy proteinuria and hypoproteinemia in comparison with UTP/CR.

Glomerular endothelial activation, C4d deposits and microangiopathy in immunoglobulin A nephropathy

Immunoglobulin A nephropathy (IgAN) is considered as mesangiopathy since it initiates in the mesangium; however, other glomerular components are involved and the glomerular capillary wall offers the first contact to circulating macromolecular IgA1. Acute and active forms of IgAN are associated with endocapillary hypercellularity and vascular damage of various degrees, in severe cases with microangiopathy (MA) without or with thrombosis [thrombotic microangiopathy (TMA)]. Vascular damage activates complement and coagulation cascades. A defective complement regulation has recently been detected in active and progressive cases of IgAN. C4d deposits in renal biopsies have been found to be an early risk factor. These observations have raised interest in manifestation of MA and TMA in progressive cases of IgAN. MA–TMA lesions have been found in various percentages (2–53%) of patients with IgAN according to patients’ selection and pathology definition of TMA. The association with hypertension (HTN) was so strong that it led to the hypothesis that MA/TMA in IgAN was a mere consequence of severe HTN. Old and new clinical and experimental data indicate that in IgAN the interaction of the glomerular capillary wall with immune reactants and complement uncontrolled activation leading to C4b deposits favours the development of MA–TMA, which plays a role in progression and renal function decline. The central role of complement activation is relevant also for the new therapeutic interventions offered by the pharma.