An increased polymeric IgA level is not a prognostic marker for progressive IgA nephropathy.

BACKGROUND: Elution of IgA from renal biopsies of patients with primary IgA nephropathy (IgAN) has suggested that mesangial IgA deposits are mainly multimeric in nature. This macromolecular IgA consists of dimeric and polymeric IgA and may be derived from the circulation. In children with IgAN, circulating macromolecular IgA levels correlate with bouts of macroscopic haematuria, but in adults a correlation with disease activity is less clear. Therefore, we have designed a novel method to assess the levels of polymeric IgA (pIgA) in sera from patients and controls. METHODS: A novel precipitation assay using recombinant CD89 was developed to measure pIgA. Polymeric IgA levels were measured in serum samples obtained from healthy volunteers (n = 21) and patients with IgAN (n = 51). Subsequently, serum pIgA levels were correlated with clinical parameters of disease. RESULTS: Serum pIgA levels were significantly increased in patients with IgAN. However, pIgA concentrations relative to total IgA were significantly lower in sera of patients with IgAN. No correlation was found between serum pIgA levels and clinical parameters of IgAN, such as decline of glomerular filtration rate, haematuria or proteinuria. CONCLUSIONS: Although absolute levels of serum pIgA are increased in patients with IgAN as compared with controls, levels of pIgA relative to total serum IgA are lower. No significant correlation was found between serum concentrations of pIgA and clinical parameters of disease. These data support the notion that it is not the size alone, but the physicochemical composition of the macromolecular IgA that is the key factor leading to mesangial deposition.     

Complexes of IgA with FcalphaRI/CD89 are not specific for primary IgA nephropathy

BACKGROUND: The presence of IgA together with the myeloid IgA-receptor FcalphaRI/CD89 in the circulation of patients with IgA nephropathy (IgAN) has been suggested as a specific pathogenic factor for mesangial deposition. However, in a recent study we found these complexes also in serum samples from healthy subjects. To investigate whether these circulating complexes are specific for IgAN, the levels and characteristics of IgA-CD89 complexes were analyzed in patients with IgAN and healthy controls. METHODS: Specific ELISAs with different poly- and monoclonal antibodies and a sensitive dot-blot method were used to measure IgA-CD89 levels in serum and purified IgA samples obtained from healthy volunteers (N = 30) and patients with IgAN (N = 35). Fractionated samples of purified IgA were used to compare the size characteristics of the IgA-CD89 complexes. RESULTS: Almost all CD89 in serum of patients with IgAN and controls was associated with high molecular weight IgA. Quantitative analysis of IgA-CD89 complexes in purified IgA revealed no significant difference between patients with IgAN and controls. No correlation was found between levels of IgA-CD89 complexes and clinical parameters associated with progressive IgAN. CONCLUSIONS: CD89 in the circulation is found mainly linked to high molecular weight IgA. The presence of these complexes is not specific for IgAN. Therefore, if IgA-CD89 complexes are involved in the pathogenesis of primary IgA nephropathy, additional factors are required to explain the IgA-CD89 complex-mediated renal inflammation.     

Long-term course of post-transplant mesangial IgA deposition: clinicopathologic study of nine cases

Abstract:  We conducted the present study to elucidate the fate of post-transplant mesangial IgA deposit under the long-term observation. Out of a total of 45 cases with post-transplant mesangial IgA deposition, nine cases with more than 4 yr of follow-up term were enrolled in this study, and clinicopathologic characteristics were described. The study included three men and six women with a mean age of 34.2 yr. The average observation time from the detection of mesangial IgA deposition was 6.1 yr. Three cases were categorized as recurrent IgA nephropathy, while six cases were classified into latent mesangial IgA deposition. One case with hypertension developed end-stage renal disease. The significant improvement in microscopic hematuria was observed in one recurrent IgA nephropathy case. Microscopic findings included mild mesangial stalk thickening in all but one case. IgA deposition demonstrated a significant decrease in three latent mesangial IgA deposition cases. No apparent reduction in dense deposit quantity was observed on electron microscopy. There was no association between clinicopathologic findings and the regimen of anti-immunosuppressive agents. This study showed the improvement of the disease activity did occur in both recurrent IgA nephropathy and latent mesangial IgA deposition. Further investigation of latent mesangial IgA deposition may present the important clue to the pathogenesis of IgA nephropathy.     

Significance of CD25 Positive Cells and Macrophages in Noncrescentic IgA Nephropathy

The aim of this study was to determine whether infiltration by CD25 positive cells, macrophages, and activated macrophages in the kidney is predictive of chronic histological injury and renal prognosis in adults with noncrescentic IgA nephropathy. Renal biopsies of 36 patients with noncrescentic IgA nephropathy were examined by immunohistochemistry for glomerular and interstitial CD4, CD8, and CD25 positive cells, monocytes/macrophage (Mac387), and activated macrophages (27E10). Renal injury (glomerulosclerosis, mesangial cell hypercellularity, tubular atrophy, and interstitial fibrosis) at the time of biopsy and renal prognosis (follow-up creatinine and creatinine clearance) were assessed. The mean follow-up period was 22.5 ± 16.5 months. The number of interstitial CD8 positive cells was the best predictor of renal injury at the time of biopsy, and was positively correlated with glomerulosclerosis (p = 0.04), tubular atrophy (p = 0.04), and interstitial fibrosis (p = 0.01) but not with mesangial cell hypercellularity. The number of interstitial Mac387 and 27E10 positive cells were the best predictors of renal prognosis (r² = 0.33 and 0.34 respectively, both p < 0.01). These data suggest the presence of CD8 cells and macrophages in the kidney at the time of biopsy could potentially serve as pathological markers to identify patients with IgA nephropathy, which may warrant more aggressive medical therapy.     

Soluble fibrin formation in the mesangial area of IgA nephropathy

Background Fibrin monomer and its derivatives in blood are found in an early stage of thrombosis. When they are produced in blood, they form complexes with fibrinogen, and they exist as soluble complexes named soluble fibrin (SF). As final insoluble products, cross-linked fibrin (XFb) is often observed in mesangial areas in active types of human glomerulonephritis. To clarify the mechanisms of mesangial SF production and its relationship to XFb deposition in IgA nephropathy (IgAN), an immunohistochemical study was conducted. Methods Nineteen patients with IgAN were studied. XFb was detected in renal biopsy specimens using anti-d-dimer antibody combined with plasmin exposure. SF was detected with a monoclonal antibody (IF-43), and factor V was detected with a specific rabbit antibody. The relationships of SF staining to the disease activity index, XFb deposition, and factor V staining was evaluated. Results XFb, factor V, and SF were observed in the mesangium in 14, 11, and 8, respectively, of a total of 19 specimens. SF had frequent staining in the proliferating areas, showing a significant relationship to XFb or factor V (P < 0.05). Furthermore, XFb, factor V, and SF depositions were markedly correlated with disease activity (P < 0.001 in each case). Conclusions These findings suggest that SF is formed in the mesangial area in active IgA nephropathy accompanied by mesangial proliferation, in particular, in its early stage.     

Protective role of anti-synthetic hinge peptide antibody for glomerular deposition of hypoglycosylated IgA1

Background The KM mouse lacks endogenous genes for immunoglobulins and carries the entire human IgH locus and the IgLk transgene. Therefore, human IgA1 does not provoke a hetero-immune response. We had observed mesangial IgA deposits in KM mice given desialo-degalacto (DeS/DeGal) IgA1. Methods In this study, the mice were immunized with synthetic IgA1 hinge (glyco-)peptide before administration of DeS/DeGal IgA1, and the effects of the pre-immunization were evaluated. Mice were divided into sHP, 5GalNAc-sHP and non-immunization groups. In two pre-immunization groups, KLH-conjugated sHP or KLH-5GalNAc-sHP, which has five GalNAc residues, was subcutaneously given three times every 2 weeks. Two weeks after the final pre-immunization, DeS/DeGal IgA1 was administered daily for 5 weeks. Serial serum levels of anti-sHP and anti-IgA1 antibodies were evaluated by ELISA. On the day of the last administration of IgA1, renal biopsy was performed. Results Mesangial IgA deposits were observed in all non-immunized mice. In pre-immunized mice, IgA deposition was not detected in 6 of 13 sHP mice and 1 of 4 5GalNAc-sHP mice. The intensities of IgA deposits were significantly different between sHP groups and non-immunized (P = 0.003) groups. There was a significant inverse correlation between the intensities of IgA deposits and the anti-sHP antibody titers (P = 0.016). Conclusions These results suggest that the anti-IgA1 hinge peptide antibody plays a role in the inhibition of glomerular IgA deposition.     

Enzymatically deglycosylated human IgA1 molecules accumulate and induce inflammatory cell reaction in rat glomeruli.

BACKGROUND: Previously, we have been able to isolate IgA1 from IgA nephropathy (IgAN) patients, that could accumulate in rat glomeruli (glomerulophilic IgA1). The 'glomerulophilic IgA1' was determined to be under-O-glycosylated in its hinge region, suggesting that under-O-glycosylation in the IgA1 hinge region plays a role in its glomerular deposition in IgAN. To confirm this, the accumulation of enzymatically under-glycosylated IgA1 in rat kidney was examined. METHODS: Human IgA1 was isolated from healthy individuals by Jacalin-affinity chromatography. Desialylated (deS IgA1) or further degalactosylated IgA1 (deS/deGal IgA1) molecules were then prepared using neuraminidase and beta-galactosidase. Two or five mg of IgA1 were injected into the left renal artery of Wistar rats. The rats were sacrificed at various time intervals (3, 9, 24 h) and the perfused part of the renal cortex was removed for immunofluorescence and for light and electron microscopy. RESULTS: Distinct amounts of deS IgA1 and deS/deGal IgA1 were observed in rat glomeruli. On the other hand, untreated IgA1 molecules (native IgA1) did not show any obvious accumulation. In rats injected with under-glycosylated IgA1, accumulation of polymorphonuclear cells (PMN) was also observed. CONCLUSIONS: These results confirmed that under-glycosylation of IgA1 played an important role in the glomerular accumulation of IgA1, which was followed by infiltration of PMN into glomeruli.     

Meaning of retrograde phenotypic change of mesangial cells in IgA nephropathy

SUMMARY: Mesangial cells show phenotypic changes such as that of glomerular differentiation at the fetal stage in various nephropathies, including IgA nephropathy. Such a process seems necessary for reparative or regenerative reactions in post-inflammatory or post-injury glomerular tissues, particularly for the rearrangement of glomerular capillary networks. Glomerular sclerosis may be the end result of failure or maldevelopment of this phenotypic glomerular transformation.     

Altered P-selectin and CD44 expression in the renal tissues and peripheral blood of children with IgA nephropathy

Objective  To understand the role of P-selectin (CD62P) and CD44 in mediating immune inflammation in the nephrotic process of children with IgA nephropathy (IgAN), cooperative expression of CD62P and CD44 in peripheral blood and renal tissues of IgAN children was investigated and its association with changes of histopathologic, serologic, and urinary properties was tested. Material and methods  Forty-six IgAN children were divided into three groups according to pathologic grades and clinical features. Fifteen blood samples from normal children and four normal renal biopsy specimens were used as controls. Plasma level of CD62P was detected by double antibody sandwich immunoradiometric assay; ELISA was used to determine serum level of CD44. Expression of CD62P and CD44 in renal tissues was determined by immunohistochemistry. Results  Cooperative expression of CD62P and CD44 was detected in renal tissues and peripheral blood of IgAN children. Altered expression of CD62P and CD44 in peripheral blood significantly correlated not only with hematuria, proteinuria, serum cholesterol, and albumin, and with urine NAG and β₂-MG, but also with degree of tubulointerstitial injury in IgAN children. Conclusion  The evidence supported CD62P and CD44 as initial and promoting factors mediating immune inflammation in the nephrotic process in IgAN children. The cooperative expression profiles of CD62P and CD44 in renal tissues and peripheral blood combined with serologic and urinary predictors may be important in diagnosis of progression in children with IgAN.     

Demonstration of secretory IgA in kidneys of patients with IgA nephropathy.

BACKGROUND: Recently we reported a possible role for secretory IgA (SIgA) in IgA nephropathy (IgAN), as suggested by increased serum levels in patients with active disease and accumulation of SIgA in a glomerular eluate. Therefore, we attempted to find support for these findings by analysis of the presence of SIgA in biopsies of IgAN patients. METHODS: Renal biopsies of 26 patients with biopsy-proven IgAN were analysed for the presence of SIgA and complement proteins. RESULTS: In 15% mesangial deposition of SIgA was demonstrated, using a specific staining for secretory component (SC) and colocalization with IgA. The presence of SIgA in these biopsies showed a strong correlation with deposition of mannose-binding lectin (MBL) and C4d. Moreover, we observed a strong colocalization between SIgA and MBL or C4d. This local complement activation has previously been linked to more severe renal disease. CONCLUSIONS: Therefore, these data provide additional evidence for a pathogenic role for SIgA in IgA nephropathy.     

Expression of mesangial IgA nephropathy in a family with several HLA-dentical members

SUMMARY: The familial incidence of mesangial IgA nephropathy (IgAN) is well recognized. However, the genetic implications of this finding remain uncertain. We report a family of East Timorese origin where six out of eight members, including the mother and five first-degree offspring, have had histologically proven mesangial IgAN. All eight members have undergone HLA A, B, C and DR typing as well as determination of C4 allotype. Among the offspring, there are HLA-identical male twins (A11,-; B13,15; Cw3,-; DR2,3) and three HLA-identical females (A11,-; B13,27; Cw3,-; DR2,3). Their C4 allotype is also identical (i.e. A3; B1,2,96 and A3; B1,96, respectively). There were histological and biochemical differences between the twins: subject ii-2 showed focal mesangial proliferation on light microscopy and a 24 h urine protein excretion of 1–2 g on presentation while subject ii-3 was normal at that time. the latter subsequently underwent a renal biopsy 15 years later and this showed changes only on immunofluorescence microscopy. There were major differences in expression of renal disease among the HLA-identical sisters: two developed end-stage renal failure (ESRF) by the age of 30 years, while the third retains normal renal function after 15 years follow-up. the angiotensin converting enzyme (ACE) genotype was examined for insertion (I)/deletion (D) polymorphism; this showed that both patients with severe renal disease had the ID genotype and this was also present in the two unaffected female members. the study shows no relationship between the HLA A, B, C, DR, C4 supratype and progress of renal disease in this family with mesangial IgAN. Moreover, no association could be demonstrated between progress and the ACE genotype, although the number of patients involved was small. the data suggest that environmental factors and/or genetic/environmental interaction influence the severity of renal injury.     

Specific binding of circulating IgA antibodies in patients with IgA nephropathy

Detection of circulating IgA antibodies which are specific in patients with IgA nephropathy is described. Freeze and thawed extracts of pharyngeal cells obtained from patients with IgA nephropathy, other glomerular diseases, and healthy adults were cultured with fibroblasts such as Vero or Hel cells at 37 degrees C for 2 weeks. Serum samples were obtained from these patients and healthy adults. The cultured fibroblasts were fixed on slide glasses, and then incubated with the serum samples from the same or other patients with IgA nephropathy. The cells were stained with FITC-labeled heavy-chain specific anti-human IgA antiserum and then examined with a fluorescent microscope. It was demonstrated that the IgA antibodies in sera obtained from patients with IgA nephropathy or HSP nephritis were bound with the nuclear regions of such fibroblasts. It was suggested that IgA antibodies in sera could be bound with some antigenic substances which were transferred from pharyngeal cells of patients with IgA nephropathy to fibroblasts in vitro.     

Glomerulonephritis in Henoch-Schöenlein purpura without mesangial IgA deposition

Ten patients with Henoch-Schöenlein purpura (HSP) were selected for study because their early renal biopsies showed focal and segmental hypercellularity, with IgA present only in deposits at the periphery of the lobules. Mesangial deposits of IgA were absent. All had laboratory evidence of nephrotic syndrome and/or renal compromise. The glomerular hypercellularity was largely the result of the infiltration of monocytes whose cytoplasm often contained tubular lysosomes and wrapping lysosomal membranes, evidence of monocyte activation. Mean levels of C3 were normal but those of C4 and properdin significantly depressed. This complement profile, as well as a glomerular monocytic infiltrate, are also seen in essential cryoglobulinemia in the adult. Of follow-up biopsies in six patients, the glomeruli were normal in three, with no IgA deposition. In the other three, mesangial deposits of IgA typical of HSP were present. The initial focal-segmental glomerulitis of these patients appeared to be the benign first phase of a disease which had the potential to culminate in mesangial IgA deposition. Patients like the three who escaped mesangial IgA would be among those responsible for the observed dissociation between severity of the initial illness and ultimate prognosis.     

Effects of angiotensin II blockade on nitric oxide blood levels in IgA nephropathy.

BACKGROUND: The effects of renin-angiotensin system blockade on nitric oxide (NO), especially in pathological conditions, are far from being established. The influence of kinins and angiotensin type 2 receptor are largely speculative and based mainly on animal studies. This study was aimed to address these aspects in humans. METHODS: Eight IgA nephropathy patients with documented clinical and histological indicators of poor prognosis were given 50 mg of losartan, 10 mg of enalapril, and 40 mg of the NO donor isosorbide 5 mononitrate (as a control of NO generation) in randomized order for 7 days each. Treatment periods were separated by washout periods of 7 days each. Laboratory investigations were performed before and after each study period. Seven healthy controls received losartan and enalapril according to the same study design. RESULTS: Glomerular filtration rate remained stable while effective renal plasma flow increased with each treatment (P<0.05). Under losartan and enalapril, filtration fraction fell (P=0.02), plasma renin activity increased (P<0.05) and urinary aldosterone concentration decreased (P=0.02). Angiotensin-converting enzyme activity was reduced to the limit of detection under enalapril (P<0.001). Blood NO, detected as nitrosylhaemoglobin by a recently developed technique of spin-trap electron paramagnetic resonance, increased significantly, as expected, during treatment with isosorbide 5 mononitrate (P=0.01), with enalapril (P<0.05), and also with losartan (P<0.05). Unlike losartan, enalapril significantly reduced albuminuria (P=0.01) in this short-term period. In the seven healthy controls, neither enalapril nor losartan were able to increase blood NO levels significantly. CONCLUSIONS: Blood levels of nitrosylhaemoglobin, a surrogate marker of NO, increased under blockade of the renin-angiotensin system in patients with IgA nephropathy, but not in healthy volunteers. This increase could contribute to changes of effective renal plasma flow in renal disease states.     

The fate of glomerular mesangial IgA deposition in the donated kidney after allograft transplantation

OBJECTIVE: To investigate the fate of the mesangial IgA deposits in the donor kidney after allograft transplantation. METHODOLOGY: Routine pre-transplant cadaveric donor kidney biopsy and repeated renal biopsies were performed at months 1, 3, and 6 after renal transplantation. The patients, 342 in number, were divided into IgA positive deposition kidney group (group A, n = 83) and non-IgA deposition kidney group (group B, n = 259). There were no significant differences between the two groups' sex, age, time of hemodialysis, warm ischemia time, cold ischemia time, complement-dependent cytotoxicity, level of panel-reactive assay, and the distribution of original disease. RESULTS: Recipients in group A received donor kidney with glomerular mesangial proliferation and marked diffuse granular IgA deposition. All of them showed edema, nephrotic range protienuria, microhematuria, hypoalbuminemia, hypertension, and delayed graft function. Borderline change was higher in group A than in group B, 37.3 and 16.2% (p < 0.001), respectively. Acute allograft rejection was higher in group A than in group B, 31.3 and 19.3% (p < 0.001), respectively. The glomerular mesangial IgA deposits gradually disappeared from the mesangial regions in grafts of acute rejection. Graft survival in both groups was not significant, being 93.8 and 95.6% in 1 yr, and 86.7 and 88.3% in 3 yr. CONCLUSION: Clinical features of the recipients which received from donor kidney with glomerular mesangial proliferation and marked diffuse granular IgA deposition: edema, proteinuria, microhematuria, hypoalbuminemia, hypertension, and delayed graft function. The presence of IgA deposits on donated kidney, by a possible increase of the immunogenicity of these kidneys, might be a cause of increased rejection. There were no significant differences between the two groups on long-term allograft survival.     

呈局灶节段性肾小球硬化的IgA肾病临床病理特点

目的探讨呈局灶节段性肾小球硬化（FSGS）的IgA肾病（IgAN）的临床和病理特点。方法选取我院1988年1月至2002年2月经肾活检确诊为IgAN的患者587例,其中呈FSGS85例,呈弥漫性系膜增生性肾小球肾炎（MsPGN）162例,呈弥漫性系膜增生性肾小球肾炎伴局灶节段性肾小球硬化（MsPGN伴FSGS）185例,比较3种类型IgAN临床和病理资料。结果FSGS型IgAN占同期所有IgAN的14．5％,临床类型以大量蛋白尿型为主,占37．64％。肾小球球囊黏连发生率高达74．12％,小管间质纤维化发生率97．65％,病理分级以LeeⅣ～Ⅴ级为主,免疫病理以IgA—MG型为主,与MsPGN伴FSGS型和MsPGN型的IgAN相比,FSGS型IgAN病程较长,高血压、肾功能不全发生率较高（P〈0．05）,而血尿的发生率与后两者无明显区别。结论呈FSGS型IgAN大量蛋白尿、高血压、肾功能不全的发生率高,病变较重,预后较差。