EMBRANOUS glomerulonephritis, a major cause of the nephrotic syndrome and chronic renal insufficiency, is associated with a wide spectrum of infections, cancers, autoimmune diseases, and drugs. The condition is characterized by an accumulation of immune deposits on the outer aspect of the glomerular basement membrane, but the target antigens have not been identified. Major contributions to our current understanding of the disease come from Heymann's nephritis, a rat model of membranous glomerulonephritis induced by immunization with an antigenic fraction of the renal brush border. 1 Studies of this experimental rat model led to the identification of megalin, a unique constitutive antigen expressed on the podocyte. 2,3 Although megalin has been found in human proximal tubules, it has not been found in human glomeruli or in immune deposits in patients with membranous glomerulonephritis. 4 Dipeptidyl-peptidase IV and neutral endopeptidase are two other antigens shared by the brush border and podocytes that are involved in the formation of immune deposits in animal models; these two proteins are expressed on the human podocyte. 5,6 In this article, we report that anti-neutral endopeptidase antibodies produced by a pregnant woman were transferred to her fetus, in which a severe form of membranous glomerulonephritis developed prenatally. The mother had a deficiency of neutral endopeptidase and probably had become immunized against the antigen at the time of or after an earlier miscarriage. CASE REPORTA male infant born at 38 weeks of gestation (birth weight, 3260 g; length, 50 cm) presented with oligoanuria (urine vol-M ume, 10 ml per 24 hours), massive proteinuria (Table 1), and respiratory distress on the first day of life. His parents were unrelated, healthy persons without a family history of renal or autoimmune disease. The mother, who was 24 years old, had had a miscarriage at 14 weeks of gestation 2 months before she became pregnant with this child. Her blood pressure, findings on urinalysis, and serum creatinine concentration were normal throughout and after the pregnancy, and she took no medications. However, antenatal ultrasonography showed oligohydramnios and enlarged fetal kidneys from the 34th week of gestation. The mother's level of antineutrophil cytoplasmic antibodies, antinuclear antibodies, anti-DNA antibodies, and complement were normal.Mechanical ventilation for hypoxemia was necessary from birth to 10 days. The infant's serum creatinine concentration was 1.9 mg per deciliter (170 µmol per liter) on day 2 and peaked at 2.7 mg per deciliter (240 µmol per liter) on day 4. Diuresis increased after the administration of intravenous furosemide. The serum creatinine concentration subsequently decreased, and nephrotic-range proteinuria developed (Table 1), as did hypoalbuminemia (1.9 g per deciliter on day 7). Calcium-channel blockers and beta-blockers were needed for blood-pressure control from day 5 until 6 weeks after birth. Urinary protein excretion progressively decreased to 4.2 mg per milligram of cr...
Randomized trials of rituximab in primary membranous nephropathy (PMN) have not been conducted. We undertook a multicenter, randomized, controlled trial at 31 French hospitals (NCT01508468). Patients with biopsy-proven PMN and nephrotic syndrome after 6 months of nonimmunosuppressive antiproteinuric treatment (NIAT) were randomly assigned to 6-month therapy with NIAT and 375 mg/m intravenous rituximab on days 1 and 8 (n=37) or NIAT alone (n=38). Median times to last follow-up were 17.0 (interquartile range, 12.5-24.0) months and 17.0 (interquartile range, 13.0-23.0) months in NIAT-rituximab and NIAT groups, respectively. Primary outcome was a combined end point of complete or partial remission of proteinuria at 6 months. At month 6, 13 (35.1%; 95% confidence interval [95% CI], 19.7 to 50.5) patients in the NIAT-rituximab group and eight (21.1%; 95% CI, 8.1 to 34.0) patients in the NIAT group achieved remission (P=0.21). Rates of antiphospholipase A2 receptor antibody (anti-PLA2R-Ab) depletion in NIAT-rituximab and NIAT groups were 14 of 25 (56%) and one of 23 (4.3%) patients at month 3 (P<0.001) and 13 of 26 (50%) and three of 25 (12%) patients at month 6 (P=0.004), respectively. Eight serious adverse events occurred in each group. During the observational phase, remission rates before change of assigned treatment were 24 of 37 (64.9%) and 13 of 38 (34.2%) patients in NIAT-rituximab and NIAT groups, respectively (P<0.01). Positive effect of rituximab on proteinuria remission occurred after 6 months. These data suggest that PLA2R-Ab levels are early markers of rituximab effect and that addition of rituximab to NIAT does not affect safety.
The phospholipase A 2 receptor (PLA 2 R) is the major target antigen in idiopathic membranous nephropathy. The technique for measuring antibodies against PLA 2 R and the relationship between antibody titer and clinical characteristics are not well established. Here, we measured anti-PLA 2 R (aPLA 2 R) antibody titer and subclass in a well defined cohort of 117 Caucasian patients with idiopathic membranous nephropathy and nephrotic-range proteinuria using both indirect immunofluorescence testing (IIFT) and ELISA. We assessed agreement between tests and correlated antibody titer with clinical baseline parameters and outcome. In this cohort, aPLA 2 R antibodies were positive in 74% and 72% of patients using IIFT and ELISA, respectively. Concordance between both tests was excellent (94% agreement, k=0.85). Among 82 aPLA 2 R-positive patients, antibody titer significantly correlated with baseline proteinuria (P=0.02). Spontaneous remissions occurred significantly less frequently among patients with high antibody titers (38% versus 4% in the lowest and highest tertiles, respectively; P,0.01). IgG4 was the dominant subclass in the majority of patients. Titers of IgG4, but not IgG1 or IgG3, significantly correlated with the occurrence of spontaneous remission (P=0.03). In summary, these data show high agreement between IIFT and ELISA assessments of aPLA 2 R antibody titer and highlight the pathogenetic role of these antibodies, especially the IgG4 subclass, given the observed relationships between aPLA 2 R titer, baseline proteinuria, and outcome.
Rituximab induces nephrotic syndrome (NS) remission in two-thirds of patients with primary membranous nephropathy (MN), even after other treatments have failed. To assess the relationships among treatment effect, circulating nephritogenic anti-phospholipase A 2 receptor (anti-PLA 2 R) autoantibodies and genetic polymorphisms predisposing to antibody production we serially monitored 24-hour proteinuria and antibody titer in patients with primary MN and long-lasting NS consenting to rituximab (375 mg/m 2 ) therapy and genetic analyses. Over a median (range) follow-up of 30.8 (6.0-145.4) months, 84 of 132 rituximabtreated patients achieved complete or partial NS remission (primary end point), and 25 relapsed after remission. Outcomes of patients with or without detectable anti-PLA 2 R antibodies at baseline were similar. Among the 81 patients with antibodies, lower anti-PLA 2 R antibody titer at baseline (P=0.001) and full antibody depletion 6 months post-rituximab (hazard ratio [HR], 7.90; 95% confidence interval [95% CI], 2.54 to 24.60; P,0.001) strongly predicted remission. All 25 complete remissions were preceded by complete anti-PLA 2 R antibody depletion. On average, 50% anti-PLA 2 R titer reduction preceded equivalent proteinuria reduction by 10 months. Re-emergence of circulating antibodies predicted disease relapse (HR, 6.54; 95% CI, 1.57 to 27.40; P=0.01), whereas initial complete remission protected from the event (HR, 6.63; 95% CI, 2.37 to 18.53; P,0.001). Eighteen patients achieved persistent antibody depletion and complete remission and never relapsed. Outcome was independent of PLA2R1 and HLA-DQA1 polymorphisms and of previous immunosuppressive treatment. Therefore, assessing circulating anti-PLA 2 R autoantibodies and proteinuria may help in monitoring disease activity and guiding personalized rituximab therapy in nephrotic patients with primary MN.
We initially selected 35 cases (pilot cohort) of PLA2R-negative MN on kidney biopsy for analysis by tandem mass spectrometry (MS/MS), and detected the unique protein, NELL-1,
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