Glomerular electron-dense deposits in childhood IgA nephropathy

Summary An electron-microscopic study of the glomeruli was made on 154 children with IgA nephropathy and no evidence of systemic disease, in whom immunofluorescence microscopy had shown diffuse mesangial deposition of IgA. Mesangial deposits were observed in all but eight children. Subepithelial deposits were observed in 40 children and were almost always accompanied by both mesangial and subendothelial deposits. Subepithelial deposits were significantly associated with more severe clinical presentations, a worse outcome and more severe light microscopic glomerular changes. These observations support the concept that IgA nephropathy is an immune complex disease.     

Mesangial electron-dense deposits in membranous nephropathy

In the absence of lupus, mesangial electron-dense deposits in membranous nephropathy are thought to be uncommon. In this study 18 renal biopsies of 16 cases seen over a 2-year period were evaluated by light and electron microscopy and immunofluorescence, directing particular attention to the mesangium. Lupus had been excluded in every instance by the usual serologic tests. In seven of the 18 biopsies, mesangial electron-dense deposits were found. Clinically, almost all of these patients were characterized by atypical features: five patients had underlying diseases which have been associated with membranous nephropathy (renal vein thrombosis, epidermoid carcinoma of the lung, SH-antigenemia, rheumatic heart disease and penicillamine therapy); there was one instance of spontaneous remission and another patient who progressed to terminal renal failure in less than 2 years. The results suggest that the presence of mesangial deposits in membranous nephropathy may be more common than has previously been suspected. This finding is not necessarily associated with systemic lupus erythematosus and may indicate an unusual or atypical form of membranous nephropathy.     

IgA nephropathy with subendothelial deposits

Summary IgA nephropathy with subendothelial deposits in the capillary walls of the glomeruli (IgA type 2) was compared histometrically and clinically with IgA nephropathy without subendothelial deposits (IgA type 1) and membranoproliferative glomerulonephritis with subendothelial deposits (MPGN). Study cases consisted of 32 biopsies from 26 patients of IgA type 1, 25 biopsies from 20 patients of IgA type 2 and 31 biopsies from 27 patients of MPGN. Histological changes of the glomeruli consisted of an increase in the mesangial matrix and hypercellularity in the mesangium in both types of IgA nephropathy, and the degree of the changes was a little higher in IgA type 2 than in IgA type 1 (0.02<P<0.05). Mesangial changes of MPGN were marked as compared with IgA type 1 and IgA type 2 (P< 0.001). Histometry of the mesangium on the cases followed up showed that the degree of mesangial thickening increased with lapse of time in IgA type 2 and MPGN, whereas it remained unchanged up to 13 years in IgA type 1. Proteinuria tended to be mild in IgA type 1, moderate in IgA type 2, and marked in MPGN. The impairment of renal function was observed in 21.9% of IgA type 1, in 36.0% of IgA type 2 and in 58.1% of MPGN. IgA type 2 has been shown to be pathologically and clinically intermediate between IgA type 1 and MPGN. These results suggest that there is a clinicopathological overlap between IgA nephropathy and MPGN with IgA deposition.     

Defective immunoglobulin A (IgA) glycosylation and IgA deposits in patients with IgA nephropathy

Defective glycosylation and immune complex (IC) formation may be of primary importance in immunoglobulin A nephropathy (IgAN) pathogenesis. The aim of this study was to determine whether defective IgA1 glycosylation might support renal deposition of IgA and disease activity. IgA was isolated from the serum of 44 IgAN patients and 46 controls and glycosylation analysed by ELISA using glycan‐specific lectins. IgA was measured by immunodiffusion and immune complexes by ELISA. IgA subclasses in IC deposits in kidney glomeruli were identified by immunohistochemical methods. A significant increase in N‐acetylgalactosamine (GalNAc) in terminal position (p = 0.02) observed in some of the IgAN patients, became more pronounced when sialic acid was removed from IgA1, indicating enhanced expression of α‐2,6‐sialyltransferase in patients compared with controls (p < 0.0001). Patients with defective galactosylation had lower serum IgA than other IgAN patients (p = 0.003). IgAN patients with both IgA1 and IgA2 glomerular deposits (21.7%) had increased GalNAc in terminal position (p = 0.003). Taken together, our results show that increased IgA glycosylation in IgAN associates with low levels of IgA, concomitant IgA1 and IgA2 glomerular deposits and poor clinical outcome.     

粘附分子选择素在IgA肾病中变化的临床意义

目的：为探讨ＩｇＡ肾病患者血和肾组织中Ｐ选择素必变与疾病的关系。方法：采用酶联免疫吸附法、免疫组化及原位杂交技术检测了４５例ＩｇＡ肾病患者血浆和肾组织中Ｐ选择素含量及表达水平。结果：ＩｇＡ肾病患者血浆Ｐ选择素含量明显高于正常人,其中肾病综合征组和肾功能减退组含量又较肉眼血尿组、尿检异常组和肾炎综合征组显著增高造反素在患者肾组织中广泛表达,其中在Ⅳ级和Ⅴ级ＩｇＡ肾病肾小球中表达水平明显高于Ⅱ级和Ⅲ级     

Charge distribution of plasma IgA in IgA nephropathy.

The spectrotype of plasma IgA in patients with IgA nephropathy was studied by isoelectric focussing. Densitometry of the gels showed a significant increase in the anionic region at isoelectric points (pI) 4.7-5.1 (P = 0.02) and a reduction in the cationic region pI 5.8-6.0 (P = 0.03) in patients (n = 15) compared with controls (n = 8). Measurement of the IgA concentration in eluates of sequential slices of the gels showed that the ratio of anionic-to-cationic IgA, using pI 5.6 as the dividing point, was significantly greater in patients (n = 10) than in controls (n = 10) (P = 0.03). Two different methods of analysis have therefore demonstrated an increased proportion of anionic and decreased proportion of cationic IgA in the plasma of patients with IgA nephropathy.     

Binding of IgA to erythrocytes from patients with IgA nephropathy

Primate erythrocytes (RBCs) may be involved in the transport and processing of C3b-containing immune complexes (IC). Compared to RBCs from healthy controls, increased amounts of IgA were detectable on RBCs from 7 of 17 patients with IgA nephropathy (IgA NP). There was no difference in the amount of IgG or IgM. The highest amount of RBC-bound IgA corresponded to 6 ng IgA/10(8) cells. The mechanisms involved in the binding of IgA to RBCs were investigated in vitro. Isolated IgA1 or IgA2 did not bind to RCBs from a patient with IgA deficiency. In contrast, incubation of RBCs with a polyethyleneglycol (PEG) precipitate of serum from a patient with IgA NP which contained IgA-IC resulted in IgA1 binding. However, this binding was not inhibited by monoclonal anti-CR1 or by an excess of IgG or IgM. Factor I did not cause release of IgA from RBCs from patients with IgA NP. Heat-aggregated IgA1 also bound to RBCs and this binding was not affected by the presence of complement. We conclude that minute amounts of IgA-IC are bound to RBCs by a complement- and Fc receptor-independent mechanism. The quantity of IgA-IC associated with RBC is so small that it is unlikely to represent an important in vivo route of IgA-IC transport or processing.     

Detection of polymeric IgA in glomeruli from patients with IgA nephropathy.

A study on the detection of polymeric IgA in glomeruli from renal biopsy specimens in patients with IgA nephropathy is described. Renal biopsy specimens were obtained from patients with IgA nephropathy. These specimens were stained with FITC-labelled anti-human J chain antisera and then examined with a fluorescent microscope. The J chain was observed in the glomerular mesangium by immunofluorescent staining. In parallel studies, renal biopsy specimens were treated with citrate buffer (pH 3.2) and the 'eluate' was neutralized by sodium hydroxide. The eluate was labelled with iodine-125, and the radiolabelled 'eluate' was fractionated by sucrose density-gradient ultracentrifugation. Polymerized IgA in the 'eluate' obtained from patients with IgA nephropathy was found to sediment predominantly as 9S to 11S using a sucrose density gradient analysis. Polymeric IgA in the fractions of the density gradient analysis was determined by anti-human IgA and anti-human J chain antisera. It was demonstrated that IgA and J chain were eluted from the glomeruli in some patients with IgA nephropathy. It is concluded that IgA deposited in the glomeruli is composed of dimers and/or larger polymers of circulating IgA in some patients with IgA nephropathy.     

Clearance kinetics and fate of macromolecular IgA in patients with IgA nephropathy

IgA glomerulonephritis is associated with macromolecules of polymeric IgA in the circulation and mesangial deposits. An impairment in the reticulophagocytic function of patients with IgA nephropathy has been postulated as the potential cause for persistence of IgA immune complexes in the circulation and their eventual glomerular deposition. Since the fate and removal mechanisms of circulating macromolecular IgA are unknown in humans, we examined the blood clearance and organ uptake of purified IgA polymers and macromolecules in patients with IgA nephropathy and normal controls. The IgA macromolecules were prepared by covalent cross-linking of purified human polymeric IgA with a heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio) propionate. After intravenous injection, large IgA molecules were removed rapidly from the circulation of patients (t1/2 = 3.8 +/- 1.0 minutes) and controls (t1/2 = 4.9 +/- 1.5 minutes). Dynamic gamma camera scintigraphy revealed the liver as the major organ that mediated the removal of the macromolecular IgA with no significant difference in the rate of hepatic uptake for patients (t1/2 = 3.4 +/- 0.6 minutes) and controls (t1/2 = 3.3 +/- 0.9 minutes). No significant amount of radioactivity could be detected in the lungs, kidneys, and spleen. The small polymers had a slower and similar clearance rates for patients (t1/2 = 29.3 +/- 7.9 h) and controls (t1/2 = 29.0 +/- 8.6 h). These findings have general significance in showing the liver as a major organ for removal of macromolecular IgA. In addition, the results have specific importance in showing that patients with IgA nephropathy do not suffer from an IgA removal dysfunction.     

The immunochemical characterization of the light chains in the mesangial IgA deposits in IgA nephropathy

The immunochemical characterization of the light chains of the mesangial immunoglobulin A (IgA) deposits were studied in 45 patients with IgA nephropathy. Kappa and lambda light chains were detected with direct immunofluorescence (IF) method, using monospecific rabbit anti-human anti-kappa and anti-lambda anti-sera. The glomeruli of 42 renal biopsies studied were strongly positive for lambda light chain, while only 25 specimens were positive for kappa light chain. Sixty-five percent of the biopsies showed a predominance of lambda light chain IF staining in the mesangial deposits. This IF pattern is unique as compared with similar studies on renal biopsies from patients with systemic lupus erythematosus, idiopathic membranous nephropathy, and normal postmortem renal tissue. The results indicate that mesangial IgA deposits in IgA nephropathy consist mainly of IgA with lambda light chains despite the fact that the normal ratio of kappa to lambda light-chain-containing immunoglobulin in human serum is two to one.     

CD44和CD62P在IgA肾病中变化的临床意义

目的　观察IgA肾病患者外周血粘附分子CD44 (细胞表面糖蛋白 )和CD6 2P (P选择素 )表达水平的变化 ,并探讨CD44和CD6 2P在IgA肾病发病中的作用及临床意义。方法　采用流式细胞术 ,对 40例IgA肾病患者外周血CD44和CD6 2P表达进行研究 ,以 36例正常人作为对照。结果　IgA肾病患者外周血CD44、CD6 2P的表达分别为 33.89%± 13.2 9%、8.5 8%± 5 .17%明显高于正常对照组 19.73 %± 6 .82 %、3.2 6 %± 1.76 % ,差异有显著性 (P <0 .0 1) ;其中在IgA肾病Ⅳ级和Ⅴ级患者CD44、CD6 2P的表达水平亦明显高于Ⅱ级和Ⅲ级 ;相关性检验结果显示 :IgA肾病患者外周血CD44表达水平与CD6 2P的表达水平呈显著正相关 (r=0 .39,P <0 .0 5 )。结论　CD44和CD6 2P在IgA肾病患者外周血表达增强 ,在IgA肾病的发病机制中起重要作用 ,可能参与了IgA肾病的病理发展过程。     

Redox state of urinary albumin in patients with IgA nephropathy

We examined the relationship between oxidative damage and molecular instability of urinary albumin in the urine of patients with IgA nephropathy (IgAN). As measure of oxidation, we detected the free thiol group at Cys34 in albumin (albumin-Cys34) using maleimide-PEG2-biotin reagent; because decreased levels of albumin-Cys34 are correlated with increased oxidation. The urine albumin-Cys34 level in all 30 patients with IgAN was decreased to varying extents. No correlations were found between urinary albumin/creatinine ratio and decreased urinary albumin-Cys34 level. Furthermore, decreases in urinary albumin-Cys34 were not accompanied by changes in serum albumin-Cys34. In diagonal-two-dimensional SDS PAGE analysis which reveals reduction-induced degradation of H2O2-treated human serum albumin, a similar pattern of albumin degradation was also detected in urine samples from patients with IgAN, indicating that structural alterations resulting from oxidative stress may be involved. Our findings suggest that redox state, in addition to urinary albumin concentration, may be an important indicator of post-translational modification and a potentially useful predictor of the kidney disease.     

Increase of IgA specific helper T alpha cells in patients with IgA nephropathy.

Patients with IgA nephropathy show an emergence of IgA dominant circulating immune complexes (CIC) as well as increased levels of serum IgA and/or IgA bearing peripheral blood lymphocytes. In order to elucidate immunological aberrations responsible for the increased IgA synthesis in such patients, quantitative and qualitative analysis was performed on T alpha cells which have been recently identified as possessing IgA specific helper activity on human B cells. Three different methods were employed to quantitate T alpha cells. These methods included a rosette formation of T cells with either bovine red cells coated with the IgA fraction of anti-bovine red cell antiserum or those coated with TNP and anti-TNP IgA antibody, and an analysis of T cells combined with fluorescein conjugated human IgA myeloma protein. T alpha cells were sorted by a fluorescence activated cell sorter and co-cultured with a B cell rich fraction to evaluate whether there is a qualitative difference in IgA specific helper activity between patients and healthy adults. T alpha cells were significantly increased in patients with IgA nephropathy while there were no significant changes in patients with chronic proliferative glomerulonephritis without mesangial deposition of IgA. There was no qualitative difference in IgA specific helper activity of T alpha cells between patients and healthy adults. It is suggested that increased levels of T alpha cells in patients with IgA nephropathy may be responsible for increased synthesis of IgA in such patients.     

炎症介质在IgA肾病中的临床应用价值探讨

目的探讨hs-CRP、IL-6、IL-18、TNF-α和TGF-β1在Ig A肾病中的临床应用价值。方法选取2010年6月至2013年11月肾穿刺活检确诊的Ig A肾病患者71例,根据病理Lee氏分级的结果将Ig A肾病组分为3个亚组,轻度组(Ⅰ级+Ⅱ级)32例,中度组(Ⅲ级)17例,重度组(Ⅳ级+Ⅴ级)22例;同时选取35例健康对照。检测各组血清Scr、Urea、CysC和尿UTP水平及血清炎症因子hs-CRP、IL-6、IL-18、TNF-α和TGF-β1水平,并比较各炎症因子与Scr、Urea、CysC和尿UTP的相关性。结果 Ig A肾病患者各组血清hs-CRP、IL-6、IL-18、TNF-α和TGF-β1水平逐渐增高,与健康对照组有显著性差异(P<0.05);随着疾病进展,重度组各炎症因子水平与轻度组和中度组比较有显著性差异(P<0.05);各炎症因子与Scr、Urea、CysC和尿UTP呈正相关(P<0.05)。结论炎症介质可以监测肾损伤程度,炎症损伤与Ig A肾病进展有密切关系。     

IgA肾病患者血清肽谱的差异性研究

目的 研究IgA肾病患者血清肽谱的差异性,筛选IgA肾病早期诊断的生物标记.方法 选取解放军第一八一医院肾脏科2008年8月至2009年3月就诊的患者或体检的健康人为研究对象,分为试验组和对照组,试验组为33例IgA肾病患者,对照组为10例健康志愿者、12例微小病变、10例局灶硬化和10例膜性肾病患者.ClinProt系统下采用磁珠浓缩和基质辅助激光解吸电离-飞行时间-质谱技术分析IgA肾病组与其他各组研究对象血清肽谱的差异.结果 分别筛选出5个、5个、3个、3个差异性多肽作为诊断IgA肾病与健康者、微小病变、局灶硬化、膜性肾病的潜在生物标记.结论 应用蛋白质组学技术成功建立了IgA肾病患者血清肽谱的诊断模型,为蛋白质组学技术用于IgA肾病的早期诊断提供了新的思路.     

Inhibition of neutrophil migration by serum IgA from patients with IgA nephropathy.

Previously we showed that patients with IgA nephropathy present high serum levels of polymeric IgA and that in vitro polyclonal stimulation of their peripheral blood lymphocytes results in the synthesis of a large amount of true polymeric IgA. The aim of this study was to determine if the serum of patients with IgA nephropathy was capable of suppressing the directional migration of human normal polymorphonuclear cells (PMN), as do the polymeric fractions of IgA myeloma. Incubation of controls' PMN with fresh or heat-inactivated patients' plasma impaired the casein-induced directional migration significantly more than incubation with controls' plasma. This inhibitory effect was closely linked to polymeric IgA fractions and to a lesser extent with monomeric IgA immune complexes. The removal of IgA by immunoadsorption from patients' plasma completely abolished the migration suppression observed on controls' PMN. These results suggest that the high serum levels of polymeric IgA observed in patients with IgA nephropathy, by inhibiting directional migration and phagocytosis of PMN, and probably monocytes, could facilitate the persistent circulation and renal deposition of immune complexes.     

Serum levels and in vitro production of IgA subclasses in patients with primary IgA nephropathy

Patients with primary IgA nephropathy have deposits of IgA1 in their kidneys, and increased plasma levels of macromolecular IgA1. Total serum IgA concentrations are frequently elevated, but studies on the subclass distribution have been few and conflicting. Several investigators found that production of IgA by peripheral blood lymphocytes in culture is increased. However, the distribution of the IgA subclasses produced has not been studied previously. We studied the serum IgA subclasses in 14 patients with IgA nephropathy, and found a significant (P less than 0.001) increase in IgA1 (3.71 +/- 1.34 mg/ml, mean +/- s.d.) compared with controls (1.77 +/- 1.10 mg/ml). Serum IgA2 was not different in patients and controls. The ratio of serum IgA1 to total IgA was also significantly (P less than 0.001) higher in patients (92.2 +/- 4.9%) than in controls (80.2 +/- 6.6%). Studies of immunoglobulin production by peripheral blood mononuclear cells showed a significant increase in IgA1 synthesis, expressed as a fraction of total IgA synthesis in unstimulated cultures (P less than 0.05) and in PWM stimulated cultures (P less than 0.01). Polymeric IgA and polymeric IgA1 production were not higher in patients than in controls. IgM production in unstimulated cultures was significantly (P less than 0.05) higher in patients than in controls. Together with the observed deposition of exclusively IgA1 in the mesangium, our results indicate that patients with IgA nephropathy preferentially produce antibodies of the IgA1 subclass.