Pathogenesis of IgA nephropathy

GALNT14 deficiency: connecting multiple links in the IgA nephropathy pathogenetic chain

IgA nephropathy (IgAN) is a highly prevalent type of primary glomerulonephritis. IgAN involves mesangial deposition of immune complexes leading to complement activation, inflammation, and glomerular injury. A key hit for pathogenesis involves aberrant O-glycosylation in the hinge region of IgA. Despite its prevalence, however, the mechanisms underlying IgAN remain incompletely understood. In this issue of the JCI, Prakash and colleagues used whole-exome sequencing of two IgAN probands to identify loss-of-function variants in GALNT14 leading to loss of the enzyme GalNAc-T14, which is involved in O-glycosylation. The authors then performed a classical bedside-to-bench investigation using a Galnt14-/- mouse model and connected loss of GalNAc-T14 to excess IgA production, impaired B lymphocyte homing, and defective intestinal mucus production. These findings build a more unified understanding of IgAN pathogenesis from defective O-glycosylation with loss-of-function variants in GALNT14.

New biomarkers in IgA nephropathy

Currently, IgA nephropathy (IgAN) is the most common cause of chronic renal failure in patients with primary glomerulonephritis. However, IgAN diagnosis is usually performed by collecting a renal biopsy as gold standard to visualize pathological changes in the glomeruli. The randomized nature of this invasive procedure in clinical practice, together with the need to exclude patients with contraindications, often results in a limited number of eligible people. Therefore, over the past two decades, researchers have explored new biomarkers for IgAN to meet the urgent clinical need for rapid diagnosis and prognosis, as well as realistic prediction of IgAN progression. In addition to traditional common markers with low specificity to detect renal diseases, the classical antibody targeting galactose-deficient IgA1 has been progressively discovered. In addition, new types of diagnostic or prognostic biomarkers are emerging, including microRNA, complement factors, proteases, inflammatory molecules and serum or urinary metabolite profiles.

What is new in the pathogenesis and treatment of IgA glomerulonephritis

Recently, new findings have been clarified concerning both pathogenesis and treatment of IgA nephritis. The four hits theory has been confirmed but several genetic wide association studies have allowed finding several genes connected with the pathogenesis of the disease. All these new genes apply to each of the four hits. Additionally, new discoveries concerning the microbiota and its connection with immune system and IgA generation have allowed finding out the role of the mucosa in IgA nephropathy pathogenesis. The IgA treatment is also changed included the future possibilities. The treatment of the chronic kidney disease, associated with the nephropathy, is mandatory, since the beginning of the disease. The classical immunosuppressive agents have poor effect. The corticosteroids remain an important cornerstone in any phase of the disease. More effect is related to the treatment of B cells and plasma cells. In particular, in very recent studies have been documented the efficacy of anti B cell-activating factor and anti A proliferation-inducing ligand agents. Most of these studies are to date in phase II/III. Finally, new agents targeting complement are arising. These agents also are still in randomized trials and act principally in hit 4 where the immunocomplexes in the mesangium activate the different pathways of the complement cascade.

Liquid Biopsy: A New Avenue for the Diagnosis of Kidney Disease: Diabetic Kidney Disease, Renal Cancer, and IgA Nephropathy

Kidney diseases are some of the most common healthcare problems. As the population of elderly individuals with concurrent health conditions continues to rise, there will be a heightened occurrence of these diseases. Due to the renal condition being one of the longevity predictors, early diagnosis of kidney dysfunction plays a crucial role. Currently, prevalent diagnostic tools include laboratory tests and kidney tissue biopsies. New technologies, particularly liquid biopsy and new detection biomarkers, hold promise for diagnosing kidney disorders. The aim of this review is to present modern diagnostic methods for kidney diseases. The paper focuses on the advances in diagnosing three common renal disorders: diabetic kidney disease, renal cancer, and immunoglobulin A nephropathy. We highlight the significance of liquid biopsy and epigenetic changes, such as DNA methylation, microRNA, piRNAs, and lncRNAs expression, or single-cell transcriptome sequencing in the assessment of kidney diseases. This review underscores the importance of early diagnosis for the effective management of kidney diseases and investigates liquid biopsy as a promising approach.

IgA nephropathy

IgA nephropathy (IgAN), the most prevalent primary glomerulonephritis worldwide, carries a considerable lifetime risk of kidney failure. Clinical manifestations of IgAN vary from asymptomatic with microscopic or intermittent macroscopic haematuria and stable kidney function to rapidly progressive glomerulonephritis. IgAN has been proposed to develop through a 'four-hit' process, commencing with overproduction and increased systemic presence of poorly O-glycosylated galactose-deficient IgA1 (Gd-IgA1), followed by recognition of Gd-IgA1 by antiglycan autoantibodies, aggregation of Gd-IgA1 and formation of polymeric IgA1 immune complexes and, lastly, deposition of these immune complexes in the glomerular mesangium, leading to kidney inflammation and scarring. IgAN can only be diagnosed by kidney biopsy. Extensive, optimized supportive care is the mainstay of therapy for patients with IgAN. For those at high risk of disease progression, the 2021 KDIGO Clinical Practice Guideline suggests considering a 6-month course of systemic corticosteroid therapy; however, the efficacy of systemic steroid treatment is under debate and serious adverse effects are common. Advances in understanding the pathophysiology of IgAN have led to clinical trials of novel targeted therapies with acceptable safety profiles, including SGLT2 inhibitors, endothelin receptor blockers, targeted-release budesonide, B cell proliferation and differentiation inhibitors, as well as blockade of complement components.

Immunoglobulin A nephropathy in paediatrics: An up-to-date

Immunoglobulin A nephropathy is the main cause of glomerulonephritis globally and an important aetiology of end-stage renal disease in children. It has been considered an autoimmune disease that can lead to the production of autoantibodies against abnormal IgA1 and formation of immune complexes. These autoantibodies and immune complexes deposit in the glomeruli, resulting in renal injury. At the beginning of IgA nephropathy course, most patients are asymptomatic and the first clinical manifestations in children are macroscopic hematuria and proteinuria. The diagnosis is defined by the detection of IgA mesangial deposits in kidney biopsy using immunofluorescence techniques. The Oxford MEST-C score is the most used classification to associate histological findings and clinical outcomes, being validated for application in children. Recommended treatment options are antihypertensive and antiproteinuric therapy, corticosteroids, immunosuppressive agents, and other non-pharmacological approaches. There is no ideal prognosis indicator but new perspectives are in science's scope to find possible biomarkers of the disease through OMICS's research. This review aims to summarize and to up-to-date the scientific literature on paediatric IgA nephropathy, focusing on pathophysiology, clinical findings, histopathology, current treatment, prognosis, and future perspectives.

IgA glycosylation and immune complex formation in IgAN

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. This disease, discovered in 1968, is characterized by IgA-IgG glomerular immunodeposits with a mesangial pattern. It is thought that these immunodeposits originate from the immune complexes formed in the circulation. It is hypothesized that the pathogenesis of IgAN is driven by aberrant glycoforms of IgA1 (galactose-deficient IgA1, Gd-IgA1). Gd-IgA1, in genetically susceptible individuals, represents the initiating factor for the formation of circulating immune complexes due to its recognition by IgG autoantibodies and the subsequent formation of pathogenic IgA1-IgG immune complexes. Complement activation through alternative and/or lectin pathways is likely playing an important role in the pathogenic properties of these complexes and may further upregulate local inflammatory responses and glomerular injury.

MicroRNAs in IgA nephropathy

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. It is considered that the pathogenesis of IgAN involves the ‘multiple hit theory’ and the immune-inflammatory mechanism; however, these theories have certain limitations. The gold standard for diagnosing IgAN is still renal biopsy. Although renal biopsy is accurate, it is traumatic and is associated with some risks and limitations, so there is a need for non-invasive diagnostic methods. According to recent studies, microRNAs (miRNAs) play important roles in the occurrence and development of IgAN; thus, they provide the possibility of the noninvasive diagnosis of IgAN and also have some value in predicting prognosis. This review summarizes the current research status of miRNAs in the occurrence, development, diagnosis, and prognosis of IgAN. We also highlight some interesting and challenging points that require further study.

Exploring AT2R and its polymorphism in different diseases: An approach to develop AT2R as a drug target beyond hypertension

The Angiotensin II type 2 receptor (AT2R) is one of the critical components of the renin-angiotensin system (RAS), which performs diverse functions like inhibiting cell differentiation, cell proliferation, vasodilatation, reduces oxidative stress and inflammation. AT2R is relatively less studied in comparison to other components of RAS despite its uniqueness (sex-linked) and diverse functions. The AT2R is differentially expressed in different tissues, and its gene polymorphisms are associated with several diseases. The molecular mechanism behind the association of AT2R and its gene polymorphisms with the diseases remains to be fully understood, which hinders the development of AT2R as a drug target. Single nucleotide polymorphisms (SNPs) in AT2R are found at different locations (exons, introns, promoter, and UTR regions) and were studied for association with different diseases. There may be different mechanisms behind these associations as some AT2R SNP variants were associated with differential expression, the SNPs (A1675G/A1332G) affect the alternate splicing of AT2R mRNA, A1332G genotype results in shortening of the AT2R mRNA and subsequently defective protein. Few SNPs were found to be associated with the diseases in either females (C4599A) or males (T1334C). Several other SNPs were expected to be associated with other similar/related diseases, but studies have not been done yet. The present review emphasizes on the significance of AT2R and its polymorphisms associated with the diseases to explore the precise role of AT2R in different diseases and the possibility to develop AT2R as a potential drug target.

O-glycoforms of polymeric IgA1 in the plasma of patients with IgA nephropathy are associated with pathological phenotypes

BACKGROUND

IgA1 O-glycosylation plays an important role in the pathogenesis of IgA nephropathy (IgAN). However, variations in IgA1 O-glycoforms have not been explored. We aimed to investigate the IgA1 O-glycoforms in the hinge region (HR) of polymeric IgA1 and then evaluate the association between IgA1 O-glycoforms and crescent formation in IgAN.

METHODS

The discovery cohort (cohort 1) comprised 11 crescentic IgAN patients, 10 noncrescentic IgAN patients and 10 healthy controls, and the validation cohort (cohort 2) comprised 11 crescentic IgAN patients, 9 noncrescentic IgAN patients, and 9 healthy controls. A total of 143 IgAN patients with different crescent percentages (cohort 3) were also included. Polymeric IgA1 was purified from the plasma of the participants. The variation in O-glycoforms was evaluated by estimating the molecular weights of IgA1 hinge glycopeptides using reversed-phase liquid chromatography (LC) and tandem mass spectrometry under electron-transfer/higher-energy collision dissociation (EThcD) fragmentation mode.

RESULTS

In discovery cohort (cohort 1), the numbers of GalNAc bound to one HR were lower in IgAN patients. The proportions of GalNAc3 (defined as O-glycans bound to one HR at 3 sites) and GalNAc4 were highest in crescentic IgAN patients followed by noncrescentic IgAN patients and were lowest in healthy controls (GalNAc 3: 9.92%±3.37% vs 6.65%±1.53% vs 4.05%±1.24%; P < 0.001; GalNAc4: 45.91%±4.75% vs 41.13%±2.95% vs 40.98%±2.95%; P = 0.004). The proportions of GalNAc5 and GalNAc6 were lowest in crescentic IgAN patients followed by noncrescentic IgAN patients and were highest in healthy controls (GalNAc5: 50.15%±4.27% vs 47.92%±4.09% vs 45.87%±3.79%, P = 0.028; GalNAc6: 6.58%±2.53% vs 6.04%±1.35% vs 4.65%±2.27%; P = 0.034). These results were consistent in the validation cohort (cohort 2); In another cohort with 143 patients with different crescents percentage (cohort 3), the numbers of GalNAc in polymeric IgA1 decreased with increasing percentage of crescents.

CONCLUSIONS

The numbers of GalNAc in IgA1 HRs were lower in IgAN patients, especially in crescentic IgAN patients, and may be associated with a severe IgAN phenotype.

Complement in Renal Disease as a Potential Contributor to Arterial Hypertension

OBJECTIVE

Complement deposition is prevalent in kidney biopsies of patients with arterial hypertension and hypertensive nephropathy, but an association of hypertension and complement deposition or involvement of complement in the pathogenesis of hypertensive nephropathy has not been shown to date.

METHODS

In this study, we analyzed complement C1q and C3c deposition in a rat model of overload and hypertension by subtotal nephrectomy (SNX) and in archival human renal biopsies from 217 patients with known hypertension and 91 control patients with no history of hypertension using semiquantitative scoring of C1q and C3c immunohistochemistry and correlation with parameters of renal function. To address whether complement was only passively deposited or actively expressed by renal cells, C1q and C3 mRNA expression were additionally analyzed.

RESULTS

Glomerular C1q and C3c complement deposition were significantly higher in kidneys of hypertensive SNX rats and hypertensive compared to nonhypertensive patients. Mean arterial blood pressure (BP) in SNX rats correlated well with the amount of glomerular C1q and C3c deposition and with left ventricular weight, as an indirect parameter of high BP. Quantitative mRNA analysis showed that C3 was not only deposited but also actively produced by glomerular cells of hypertensive SNX rats and in human renal biopsies. Of note, in patients CKD-stage correlated significantly with the intensity of glomerular C3c staining, but not with that of C1q.

CONCLUSION

Renal complement deposition correlated with experimental hypertension as well as the presence of hypertension in a variety of renal diseases. To answer the question, if and how exactly renal complement is causative for the pathogenesis of arterial hypertension in men, further studies are needed.

TLR7 in B cells promotes renal inflammation and Gd-IgA1 synthesis in IgA nephropathy

TLR7 has been linked to the pathogenesis of glomerulonephritis, but its precise roles are not clear. In this study, we evaluated the roles of TLR7 in IgA nephropathy (IgAN). TLR7 proteins were abundant in CD19+ B cells infiltrated in the kidneys of patients with IgAN. The intensities of both intrarenal TLR7 and CD19 proteins were closely associated with kidney function (estimated glomerular filtration rate [eGFR] and serum creatinine concentration) and renal histopathology (tubular atrophy, leukocyte infiltration, tubulointerstitial fibrosis, and global glomerulosclerosis) in patients with IgAN. Meanwhile, TLR7 mRNA levels were significantly increased in peripheral blood B cells of patients with IgAN. TLR7+CD19+ B cells expressed inflammatory cytokines (IL-6 and IL-12) in kidneys and produced high levels of IgA1 and galactose deficient-IgA1 (Gd-IgA1) in peripheral blood of patients with IgAN. Mechanistically, TLR7 activated B cells to produce high levels of Gd-IgA1 via the TLR7-GALNT2 axis in IgAN. Protein levels of GALNT2 were increased by overexpression of TLR7, while they were reduced by TLR7 knockdown in B cells. GALNT2 overexpression augmented Gd-IgA1 production in B cells derived from patients with IgAN. Taken together, high TLR7 expression in B cells has dual roles in the development and progression of IgAN, by facilitating renal inflammation and Gd-IgA1 antibody synthesis.

Serologic and Histologic Predictors of Long-Term Renal Outcome in Biopsy-Confirmed IgA Nephropathy (Haas Classification): An Observational Study

Background and objective: The Haas classification of IgA nephropathy should be validated for Asian populations. More detailed and newer predictions regarding renal outcome of IgA nephropathy remains mandatory. Materials: We conducted a retrospective cohort study between January 2003 and December 2013. Clinical, Pathological, and laboratory data were all collected via available medical records. A Mann–Whitney U test was used for continuous variables and the Chi-square test was implemented for categorical variables. A Kaplan–Meier curve was put in place in order to determine patient survival and renal survival. The Youden index and Cox proportional hazard regression were used to investigate the possible factors for renal survival and predictive power. Results: All 272 renal biopsy-confirmed IgAN patients were enrolled for further studies. The univariate analysis showed that risk factors for poor renal outcome included stage 4–5 of Haas classification (HR = 3.67, p < 0.001), a poor baseline renal function (HR = 1.02 and p < 0.001 for higher BUN; HR = 1.14 and p < 0.001 for higher serum creatinine; HR = 0.95, p < 0.001 for higher eGFR), IgG ≤ 907 (HR = 2.29, p = 0.003), C3 ≤ 79.7 (HR = 2.76, p = 0.002), a higher C4 (HR = 1.02, p = 0.026), neutrophil-to-lymphocyte ratio > 2.75 (HR = 2.92, p < 0.001), and a platelet-to-lymphocyte ratio ≥ 16.06 (HR = 2.02, p = 0.012). A routine-checked markers, such as neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio, in order to predict the renal outcome, is recommended. Conclusions: This is the first study to demonstrate that Haas classification is also useful for establishing predictive values in Asian groups. A lower serum IgG (≤907 mg/dL) and serum C3 (≤79.7 mg/dL) were both risk factors for poor renal outcome. Additionally, this is the first study to reveal that serum C4 levels, an NLR > 2.75 and a PLR > 16.06, S could suggest poor renal outcome.

Approach to the Child with Hematuria

The causes of macroscopic and microscopic hematuria overlap; both are often caused by urinary tract infections or urethral/bladder irritation. Coexistent hypertension and proteinuria should prompt investigation for glomerular disease. The most common glomerulonephritis in children is postinfectious glomerulonephritis. In most patients, and especially with isolated microscopic hematuria, the diagnostic workup reveals no clear underlying cause. In those cases whereby a diagnosis is made, the most common causes of persistent microscopic hematuria are thin basement membrane nephropathy, immunoglobulin A nephropathy, or idiopathic hypercalciuria. Treatment and long-term prognosis varies with the underlying disease.

IgA nephropathy with diffuse alveolar haemorrhage

Immunoglobulin (Ig)A nephropathy is the most common cause of primary glomerulonephritis worldwide. While IgA nephropathy has been associated with a variety of other diseases, pulmonary complications are extremely rare. A 58-year-old man presented with a 2-week history of fever and exertional dyspnoea. A chest imaging revealed bilateral consolidation predominantly in upper lungs. Laboratory findings showed elevated serum creatinine with proteinuria and haematuria. Flexible bronchoscopy revealed diffuse alveolar haemorrhage, and IgA nephropathy was confirmed on a renal biopsy. He received prednisone with good effect. This case highlights the need to consider IgA nephropathy in the differential diagnosis of pulmonary renal syndrome.

Characteristics of patients with coexisting IgA nephropathy and membranous nephropathy

BACKGROUND

Coexistence of IgA nephropathy (IgAN) and membranous nephropathy (MN) in the same patient is rare. Few studies have reported the clinical and pathological features of patients with combined IgAN and MN (IgAN-MN).

METHODS

The clinico-pathological features, levels of galactose-deficient IgA1 (Gd-IgA1) and autoantibodies against M-type transmembrane phospholipase A₂ receptor (anti-PLA₂R) in sera were compared among IgAN-MN, IgAN, and MN patients.

RESULTS

Twenty-six patients with biopsy-proven IgAN-MN were enrolled. The mean age at biopsy was 43.6 ± 15.9 years, and 65.4% were male. Proteinuria and estimated glomerular filtration rate (eGFR) levels in patients with IgAN-MN were similar to that of MN patients. Compared with the IgAN patients, IgAN-MN patients showed a higher median proteinuria level (4.3 vs. 1.2 g/day, p < .001), and a higher mean eGFR level (101.8 ± 25.4 vs. 78.6 ± 26.9 mL/min/1.73 m², p < .001). IgAN-MN patients presented with milder pathological lesions than IgAN patients according to the Oxford Classification. IgAN-MN patients had comparable serum levels of Gd-IgA1 with those of IgAN patients (353.4 ± 95.5 vs. 347.0 ± 109.6 U/mL, p = .801). Percentage of IgAN-MN patients with detectable serum levels of anti-PLA₂R was lower than that of MN patients (38.5% vs. 68.6%, p = .011).

CONCLUSIONS

IgAN-MN patients display similar clinical features to MN patients and milder pathological lesions than IgAN patients. IgAN-MN patients have similar levels of Gd-IgA1 to those of IgAN patients, and a lower proportion of anti-PLA₂R than MN patients.

Biomarkers for IgA nephropathy on the basis of multi-hit pathogenesis

IgA nephropathy (IgAN) is the most prevalent glomerular disease worldwide and is associated with a poor prognosis. Development of curative treatment strategies and approaches for early diagnosis is necessary. Renal biopsy is the gold standard for the diagnosis and assessment of disease activity. However, reliable biomarkers are needed for the noninvasive diagnosis of this disease and to more fully delineate the risk of progression. With regard to the pathogenesis of IgAN, the multi-hit hypothesis, including production of galactose-deficient IgA1 (Gd-IgA1; Hit 1), IgG or IgA autoantibodies that recognize Gd-IgA1 (Hit 2), and their subsequent immune complexes formation (Hit 3) and glomerular deposition (Hit 4), has been widely supported by many studies. Although the prognostic values of several biomarkers have been discussed, we recently developed a highly sensitive and specific diagnostic method by measuring serum levels of Gd-IgA1 and Gd-IgA1-containing immune complexes. In addition, urinary Gd-IgA1 may represent a disease-specific biomarker for IgAN. We also confirmed that there is a significant correlation between serum levels of these effector molecules and disease activity, suggesting that each can be considered a practical surrogate marker of therapeutic response. Thus, these disease-oriented specific serum and urine biomarkers may be useful for screening of potential IgAN with isolated hematuria, earlier diagnosis, disease activity, and eventually, response to treatment. In this review, we discuss these concepts, with a focus on potential clinical applications of these biomarkers.

A genome-wide trans-ethnic interaction study links the PIGR-FCAMR locus to coronary atherosclerosis via interactions between genetic variants and residential exposure to traffic

Air pollution is a worldwide contributor to cardiovascular disease mortality and morbidity. Traffic-related air pollution is a widespread environmental exposure and is associated with multiple cardiovascular outcomes such as coronary atherosclerosis, peripheral arterial disease, and myocardial infarction. Despite the recognition of the importance of both genetic and environmental exposures to the pathogenesis of cardiovascular disease, studies of how these two contributors operate jointly are rare. We performed a genome-wide interaction study (GWIS) to examine gene-traffic exposure interactions associated with coronary atherosclerosis. Using race-stratified cohorts of 538 African-Americans (AA) and 1562 European-Americans (EA) from a cardiac catheterization cohort (CATHGEN), we identify gene-by-traffic exposure interactions associated with the number of significantly diseased coronary vessels as a measure of chronic atherosclerosis. We found five suggestive (P<1x10^-5) interactions in the AA GWIS, of which two (rs1856746 and rs2791713) replicated in the EA cohort (P < 0.05). Both SNPs are in the PIGR-FCAMR locus and are eQTLs in lymphocytes. The protein products of both PIGR and FCAMR are implicated in inflammatory processes. In the EA GWIS, there were three suggestive interactions; none of these replicated in the AA GWIS. All three were intergenic; the most significant interaction was in a regulatory region associated with SAMSN1, a gene previously associated with atherosclerosis and B cell activation. In conclusion, we have uncovered several novel genes associated with coronary atherosclerosis in individuals chronically exposed to increased ambient concentrations of traffic air pollution. These genes point towards inflammatory pathways that may modify the effects of air pollution on cardiovascular disease risk.

The clinical course of IgA nephropathy after kidney transplantation and its management

Immunoglobulin (Ig) A nephropathy is one of the most common primary glomerulonephritides worldwide causing end stage renal disease in up to 20-40% of affected patients, nearly two decades post diagnosis. Kidney transplantation is the treatment of choice for patients with renal failure, secondary to glomerular diseases. However, IgA nephropathy has a strong tendency to recur in the graft, and although initially thought to be a benign condition, several reports of graft loss, due to recurrent IgA nephropathy, there have been over the last three decades. Overall graft survival has been significantly improved in kidney transplantation, as a result of reduced incidence of acute rejection, as more potent and more specific immunosuppressive agents are now available in clinical practice. Thus, the rates of IgA nephropathy and other glomerulonephritides recurrence are expected to increase, since graft survival has been improved. However, the reported incidence of IgA nephropathy recurrence in the graft varies substantially across centers, as a consequence of different levels of interest, diverse biopsy policies and differing durations of follow up, of the published studies. Notably, recurrence rates of patients receiving graft biopsies by clinical indication only, ranges from 13% to 50% with graft loss being between 1.3% and 16%. The aim of this review is to underline important pathogenetic insights of IgA nephropathy, describe the clinical course of the disease after kidney transplantation, with emphasis on the incidence of recurrence and the associated risk factors, and finally provide all available options for its management in transplant recipients.

TGF-β1 mimics the effect of IL-4 on the glycosylation of IgA1 by downregulating core 1 β1, 3-galactosyltransferase and Cosmc

The aberrant glycosylation of IgA1 is pivotal in the pathogenesis of IgA nephropathy (IgAN). The aim of the present study was to investigate the effect of transforming growth factor‑β1 (TGF‑β1) on the glycosylation of IgA1 and the associated mechanism. The mRNA levels of core1 β1, 3-galactosyltransferase (C1GalT1) and its molecular chaperone, Cosmc, were analyzed, as was the subsequent O-glycosylation of IgA1, in a human B‑cell line stimulated with TGF‑β1. The IgA1‑positive human B‑cell line was cultured with different concentrations of recombinant human TGF‑β1 (5, 10, 15 and 30 ng/ml). The production and glycosylation of IgA1 were assayed using sandwich ELISA and enzyme‑linked lectin binding assays, respectively, and the mRNA levels of C1GalT1 and Cosmc were quantified using reverse transcription‑quantitative polymerase chain reaction analysis. The results showed that the production of IgA1 was stimulated by low concentrations of TGF‑β1 (5 or 10 ng/ml) and was suppressed by high concentrations (15 or 30 ng/ml). The terminal glycosylation of secreted IgA1 was altered in response to TGF‑β1. TGF‑β1 stimulation significantly decreased the mRNA levels of C1GalT1 and Cosmc. TGF‑β1 may be key in controlling the glycosylation of IgA1, in part via the downregulation of C1GalT1 and Cosmc.

Separation of Two Distinct O-Glycoforms of Human IgA1 by Serial Lectin Chromatography Followed by Mass Spectrometry O-Glycan Analysis

Human immunoglobulin A1 (IgA1), which carries four to six mucin-type O-glycans (O-glycans) on its hinge region (HR), is the most abundant O-glycoprotein in plasma or serum. While normal O-glycans from hematopoietic-originated cells are core 1-based complex structures, many reports showed that the IgA1 from patients with IgA nephropathy (IgAN) carries undergalactosylated or truncated O-glycans such as the Tn antigen and its sialylated version the SialylTn (STn) antigen on the HR. Yet, there is still a debate whether Tn/STn on the HR of IgA1 is specific to the IgA1 from patients with IgAN since these antigens have also been seen in serum IgA1 of healthy individuals. An additional question is whether the O-glycans at all sites on the two HRs of one IgA1 molecule are homogeneous (either all normal or all Tn/STn) or heterogeneous (both normal and Tn/STn O-glycans). To address these questions, we conducted a systematic study on the O-glycans of plasma IgA1 from both IgAN patients and healthy controls using serial HPA and PNA lectin chromatography followed by western blotting and further analysis of O-glycans from HPA-bound and PNA-bound IgA1 fractions by mass spectrometry. Unexpectedly, we found that a variable minor fraction of IgA1 from both IgAN patients and healthy controls had Tn/STn antigens, and that the O-glycoprotein IgA1 molecules from most samples had only two distinct O-glycoforms: one major glycoform with homogeneous normal core 1-based O-glycans and one minor glycoform with homogeneous Tn/STn antigens. These results raised a serious question about the role of Tn/STn antigens on IgA1 in pathogenesis of IgAN, and there is a demand for a practical methodology that any laboratory can utilize to analyze the O-glycans of IgA1. Herein, we describe the methodology we developed in more detail. The method could also be applied to the analysis of any other O-glycosylated proteins.

Mycophenolate and nephrology

Several large, randomized trials have established mycophenolate mofetil (MMF) as an effective immunosuppressant for kidney transplantation. Inhibition of inosine 5′-monophospate dehydrogenase (IMPDH) by MMF appears to have pleiotropic effects on both immune and non-immune cells. In addition to B- and T-cell inhibition, in vitro and in vivo data suggest that MMF also has inhibitory effects on smooth muscle cells, endothelial cells, and myofibroblasts, findings that may be relevant in considering treatment of primary immune mediated kidney diseases. Clinical trials have established the efficacy of MMF for the treatment of lupus nephritis, as discussed in detail elsewhere in this supplement. Although animal studies have provided the rationale for human trials of MMF in primary glomerular diseases, most of the evidence thus far is conflicting or based largely on pilot studies. Data from larger, controlled trials will soon emerge and may clarify the role of MMF in the treatment of these disorders.

Elevated Plasma α-Defensins (HNP1-3) Levels Correlated with IgA1 Glycosylation and Susceptibility to IgA Nephropathy

Aim. IgA nephropathy (IgAN) is the most common form of glomerulonephritis. Recent genome-wide association study (GWAS) suggested that DEFA locus (which encodes α-defensins) may play a key role in IgAN. Methods. The levels of α-defensins in 169 IgAN patients and 83 healthy controls were tested by ELISA. Results. We observed that α-defensins human neutrophil peptides 1–3 (HNP1–3) in IgAN patients were elevated compared with healthy controls. The mean levels of α-defensins of 83 healthy controls and 169 IgAN patients were 50 ng/mL and 78.42 ng/mL. When the results were adjusted to the mean levels of α-defensins of IgAN patients, the percentage of individuals with high levels of α-defensins increased in IgAN patients (22.5%) compared to healthy controls (9.6%) (p = 0.013). The elevation of α-defensins in IgAN patients was independent of renal function or neutrophil count, which were major sources of α-defensins in circulation. More importantly, negative correlation was observed between galactose-deficient IgA1and α-defensins. Conclusion. As α-defensin is a lectin-like peptide, we speculated that it might be involved in IgA galactose deficiency. The data implied that patients with IgAN had higher plasma α-defensins levels and high α-defensins correlated with IgA galactose deficiency, further suggesting a pathogenic role of α-defensins in IgAN.

Diffuse alveolar hemorrhage in IgA nephropathy: case series and systematic review of the literature

OBJECTIVES

To describe the spectrum of pulmonary involvement in immunoglobulin A nephropathy (IgAN).

METHODS

We describe two patients with pulmonary renal syndrome related to IgAN and a systematic review of previously reported cases of IgAN and lung involvement.

RESULTS

We identified 23 reports of IgAN-related pulmonary disease, including 19 reports of alveolar hemorrhage and two cases of organizing pneumonia. Dyspnea (84%), hemoptysis (74%), cough (53%) and fever (47%) were common presenting complaints. Simultaneous involvement of kidneys and lung was the most common presentation (42%) but alveolar hemorrhage occurred independent of renal disease in one-fifth (21%). Azotemia was seen in 55.5% at presentation. Mesangio-proliferative glomerulonephritis was the most common biopsy finding and crescentic glomerulonephritis was seen in 27.7%. Among patients undergoing lung biopsy, capillaritis was seen in 72.7%; 37.5% of these had IgA deposits. Steroids with cyclophosphamide, followed by maintenance with methotrexate or azathioprine was used in 44%. Mechanical ventilation, dialysis and plasmapheresis were other adjunctive therapies used. IgAN-related alveolar hemorrhage was associated with a mortality of 26.3% and significant morbidity, with 52.7% having end-stage kidney disease despite immunosuppression. Organizing pneumonia with pulmonary IgA deposition is a well-described association of IgAN.

CONCLUSION

These findings are similar to our previous observations of Henoch-Schonlein purpura (HSP)-related alveolar hemorrhage, highlighting the similarities of these related syndromes. Multicentric studies of IgAN and HSP-related pulmonary renal syndrome with a standard protocol are needed to define their similarities and differences, optimum suppression and its role in preventing renal progression in this setting.

Pathogenic Role of a Proliferation-Inducing Ligand (APRIL) in Murine IgA Nephropathy

A proliferation-inducing ligand (APRIL) is a member of the tumor necrosis factor (TNF) superfamily. Despite advances in clinical and genetic studies, the details of the pathological roles of APRIL in IgA nephropathy (IgAN) remain to be fully defined. The present study aimed to further assess the pathological role of APRIL using a mouse model of IgAN. Mice with IgAN designated “grouped ddY” (gddY) were intraperitoneally administered an anti-APRIL monoclonal antibody (anti-APRIL Ab) or control IgG (Control Ab) twice each week for 2 weeks starting during the early stage of IgAN (6–7 weeks of age). Urinary albumin, serum IgA, and glomerular IgA deposition were evaluated. We further assessed the inflammatory responses during treatment by measuring the levels of the chemokine fractalkine (FKN) and its receptor CX3CR1 as well as the level of peripheral blood monocytosis. Anti-APRIL Ab treatment significantly decreased albuminuria and tissue damage combined with decreases in serum IgA levels and deposition of glomerular IgA. In contrast, the abundance of IgA⁺/B220⁺ or CD138⁺/B220⁺ B cells in the spleen and bone marrow, respectively, was unchanged. Treating gddY mice with anti-April Ab reduced the overexpression of FKN/CX3CR1 in the kidney and the increase in the population of circulating Gr1⁻/CD115⁺ monocytes. The size of the population of Gr1⁻/CD115⁺ monocytes correlated with renal FKN and urinary albumin levels. Moreover, mice treated with anti-APRIL Ab exhibited reduced progression of IgAN, serum IgA levels, and glomerular IgA deposition as well as an attenuated inflammatory process mediated by FKN-associated activation of monocytes. To the best of our knowledge, this is the first study to implicate the APRIL signal transduction pathway in the pathogenesis of nephrogenic IgA production. Moreover, our findings identify APRIL as a potential target of therapy.

Outcomes following Kidney transplantation in IgA nephropathy: a UNOS/OPTN analysis

This study updates assessment of post-transplant outcomes in IgAN patients in the modern era of immunosuppression. Using UNOS/OPTN data, patients ≥18 yr of age with first kidney transplant (1/1/1999 to 12/31/2008) were analyzed. Multivariable Cox regression models and propensity score-based matching techniques were used to estimate hazard ratios (HRs) for death-censored allograft survival (DCGS) and patient survival in IgAN compared to non-IgAN. Results of multivariable regression were stratified by donor type (living vs. deceased). A total of 107, 747 recipients were included (4589 with IgAN and 103 158 with non-IgAN). Adjusted HR for DCGS showed no significant difference between IgAN and non-IgAN. IgAN had higher patient survival compared to non-IgAN (HR 0.54, 95% CI 0.47-0.62, p < 0.0001 for deceased donors; HR 0.42, 95% CI 0.33-0.54, p < 0.0001 for living donors). Propensity score-matched analysis was similar, with no significant difference in DCGS between matched groups and higher patient survival in IgAN patients compared to non-IgAN group (HR 0.54, 95% CI 0.47, 0.63; p-value <0.0001). IgAN patients with first kidney transplant have superior patient survival and similar graft survival compared to non-IgAN recipients. Results can be used in prognostication and informed decision-making about kidney transplantation in patients with IgAN.

Diagnosis and activity assessment of immunoglobulin A nephropathy: current perspectives on noninvasive testing with aberrantly glycosylated immunoglobulin A-related biomarkers

Immunoglobulin (Ig) A nephropathy (IgAN) is the most common form of glomerular disease worldwide and is associated with a poor prognosis. Thus, development of a curative treatment and strategies for early diagnosis and treatment are urgently needed. Pathological analysis of renal biopsy is the gold standard for the diagnosis and assessment of disease activity; however, immediate and frequent assessment based on biopsy specimens is difficult. Therefore, a simple and safe alternative is desirable. On the other hand, it is now widely accepted that multi-hit steps, including production of aberrantly glycosylated serum IgA1 (first hit), and IgG or IgA autoantibodies that recognize glycan containing epitopes on glycosylated serum IgA1 (second hit) and their subsequent immune complex formation (third hit) and glomerular deposition (fourth hit), are required for continued progression of IgAN. Although the prognostic and predictive values of several markers have been discussed elsewhere, we recently developed a highly sensitive and specific diagnostic method by measuring serum levels of glycosylated serum IgA1 and related IgA immune complex. In addition, we confirmed a significant correlation between serum levels of these essential effector molecules and disease activity after treatment, suggesting that each can be considered as a practical surrogate marker of therapeutic effects in this slowly progressive disease. Such a noninvasive diagnostic and activity assessment method using these disease-oriented specific biomarkers may be useful in the early diagnosis of and intervention in IgAN, with appropriate indication for treatment, and thus aid in the future development and dissemination of specific and curative treatments.

Genetic variants in interleukin genes and susceptibility to IgA nephropathy: a meta-analysis

Many existing studies have demonstrated that genetic variants in interleukin (IL) genes might have an impact on an individual's susceptibility to IgA nephropathy (IgAN); but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the relationships between IL genetic variants and IgAN risk. We searched CISCOM, CINAHL, Web of Science, PubMed, Google Scholar, EBSCO, Cochrane Library, and China BioMedicine (CBM) and China National Knowledge Infrastructure (CNKI) databases from inception through August 1, 2013. Meta-analysis was performed using the STATA 12.0 software. Seven case-control studies were included with a total of 1135 IgAN patients and 1603 healthy controls. Our meta-analysis results revealed that genetic variants in IL-1 and IL-1RN genes were associated with an increased risk of IgAN. However, similar associations were not observed in IL-6, IL-10, and IL-22R genes. Subgroup analysis by ethnicity suggested that there were significant associations between IL genetic variants and an increased risk of IgAN among both Asian and Caucasian populations. Meta-regression analyses showed that gene types may be a major source of heterogeneity. No publication bias was detected in this meta-analysis. The present meta-analysis suggests that IL genetic variants may contribute to the risk of IgAN, especially in IL-1 and IL-1RN genes.

Functional implications of regulatory B cells in human IgA nephropathy

IgA nephropathy (IgAN) diagnosis remains largely based upon immunohistologic detection of IgA- and IgG-containing glomerular deposits in renal mesangial cells, and little is known about the underlying pathogenic mechanisms. This study examines the putative contribution of B cell types, including the Breg type, to IgAN pathogenesis. Twenty-four patients with IgAN and proteinuria (Group A: <3.5 g/24 h, n = 13; Group B: >3.5 g/24 h, n = 11) and 10 healthy controls were enrolled. The frequencies of B cell subtypes in venous blood were measured by flow cytometry. Galactose-deficient IgA1 was measurement by ELISA. Needle biopsies were analysed by histology and immunofluorescence microscopy. Correlation between clinical features and B cell subtypes, including the regulatory B (Breg) cells, and Breg cell-derived immunomodulatory cytokine IL-10 was assessed by Spearman's rank correlation test. IgAN patients had significantly higher frequencies of CD27(+) CD19(+) , CD38(+) CD19(+) , CD86(+) CD19(+) and CD5(+) CD19(+) B cells than the healthy controls, but significantly lower levels of Breg cells and intracellular expression of IL-10 protein in the Breg subtype. Serum IgA concentration positively correlated with CD27(+) CD19(+) B cell frequency and negatively correlated with IL-10(+) Breg cell frequency in IgAN patients, and the percentage of CD19(+) CD5(+) CD1d(+) in CD19(+) cells was negatively correlated with the level of serum Gd-IgA1. Furthermore, the frequencies of CD19(+) CD38(+) and CD19(+) CD86(+) in the CD19(+) subpopulation negatively correlated with the estimated glomerular filtration rate of IgAN patients. Several of the CD19(+) B cell subtypes and the IL-10(+) Breg cells are differentially expressed in IgAN patients and may contribute to the disease pathogenesis.

Latent mesangial immunoglobulin A deposition in long-term functioning kidney does not correlate with disease progression and may exhibit fluctuating patterns

BACKGROUND

Latent mesangial immunoglobulin (Ig)A deposition in long-term functioning kidney does not correlate with disease progression and may exhibit fluctuating patterns Mesangial IgA deposition without urinary abnormalities (latent mesangial IgA deposition) is occasionally observed in non-episode biopsies of kidney allografts. However, the histologic features of latent IgA deposition have not been fully characterized.

METHODS

To better identify the clinicopathologic background of subclinical mesangial IgA deposition, we compared the clinical and histologic characteristics of long-term functioning kidney allografts with and without latent IgA deposition.

RESULTS

Among 29 patients with a posttransplant duration of >10 years, 37.9% exhibited latent mesangial IgA deposition. Biopsies indicated that renal function at the time of and 5 years before subclinical mesangial IgA deposition was generally similar. HLA-DR4 and HLA-Bw51 showed a nonsignificant trend to be more frequent in the IgA-positive group. Histologic investigation demonstrated no changes in disease scores based on the Banff 2009 classification between groups. Immunofluorescence revealed co-deposition of C3 at >1+ intensity in 72% IgA-positive patients. Immunohistochemical analysis revealed that IgA deposition per se did not cause notable increases in intraglomerular α-smooth muscle actin (SMA)-positive cells. One patient with subclinical IgA deposition demonstrated a waxing and waning pattern in the amount of IgA deposition.

CONCLUSION

This study suggests that subclinical IgA deposition in long-term functioning kidney allografts is not associated with progressive course in clinical and pathologic findings. Furthermore, the amount of subclinical IgA deposition may exhibit fluctuating patterns in some cases.

Proteomic analysis of whole glomeruli in patients with IgA nephropathy using microsieving

BACKGROUND

To promote understanding of immunoglobulin A nephropathy (IgAN) pathophysiology, we tried to elucidate glomerular protein profiles in IgAN, using microsieving that we established recently to isolate glomeruli from renal biopsy samples and proteomic approaches.

METHODS

Glomeruli were isolated from renal biopsy samples of patients with IgAN (n = 5) and with minimal change nephrotic syndrome (MCNS; n = 5) using microsieving. Proteins extracted from the isolated glomeruli were separated by 2-dimensional differential gel electrophoresis (2D-DIGE). Proteins with different amounts between the two groups were identified by mass spectrometry. One of the identified proteins, α-actinin-4 (ACTN4), was further analyzed by Western blotting, RT-polymerase chain reaction (PCR), and immunohistochemistry.

RESULTS

By 2D-DIGE, 72 out of the detected 1,170 protein spots showed significantly different intensity between the two groups (p < 0.05). Thirty-four out of the 72 protein spots showed more than 1.5-fold or less than 1/1.5-fold intensity, out of which 16 protein spots were successfully identified. No microbial protein was identified. ACTN4 molecules with a low molecular weight of approximately 77 kDa were found to increase in the IgAN group. Lack of an N-terminal part of ACTN4 was demonstrated by Western blotting. No defect of mRNA for ACTN4 was evidenced by RT-PCR. Predominant existence of ACTN4 in capillary walls of glomeruli of IgAN patients was demonstrated by immunohistochemistry in glomerular sections of patients with IgAN.

CONCLUSION

Use of microsieving enabled us to biochemically analyze glomerular proteins in renal biopsy samples from patients with glomerular diseases. With this method, we demonstrated skewed glomerular protein profiles in IgAN.

Th1/Th2 polarization in tonsillar lymphocyte form patients with IgA nephropathy

Imbalance of Th1/Th2 pro-inflammatory cytokines plays an important role in the development and progression of IgA nephropathy (IgAN). Clinical development and exacerbation of IgAN are frequently preceded by episodes of upper respiratory tract infection, and palatine tonsils represent the predominant immunocompetent tissue of the upper respiratory tract. This study examined tonsillar lymphocytes of IgAN who suffered from tonsillitis (n = 22), and using tonsils derived from patients with chronic tonsillitis (n = 24) but without renal disease as a control. We identified a polarization toward Th2 response in tonsils of IgAN patients. TH0 cells are differentially mobilized during contact sensitization and by adjuvants such as lipopolysaccharide (LPS) that induce T-helper type 1 (Th1) responses, or α-hemolytic streptococcus (HS) that induces T-helper type 2 (Th2) responses. Th1:Th2 ratio is correlated with proteinuria and renal pathologic changes in IgAN group. Our study suggests that IgAN is associated with the change in Th1/Th2 balance in favor of Th2 lymphocytes.

Tn and sialyl-Tn antigens, aberrant O-glycomics as human disease markers

In many different human disorders, the cellular glycome is altered. An interesting but poorly understood alteration occurs in the mucin-type O-glycome, in which there is aberrant expression of the truncated O-glycans Tn (GalNAcα1-Ser/Thr) and its sialylated version sialyl-Tn (STn) (Neu5Acα2,6GalNAcα1-Ser/Thr). Both Tn and STn are tumor-associated carbohydrate antigens and tumor biomarkers, since they are not expressed normally and appear early in tumorigenesis. Moreover, their expression is strongly associated with poor prognosis and tumor metastasis. The Tn and STn antigens are also expressed in other human diseases and disorders, such as Tn syndrome and IgA nephropathy. The major pathological mechanism for expression of the Tn and STn antigens is compromised T-synthase activity, resulting from alteration of the X-linked gene that encodes for Cosmc, a molecular chaperone specifically required for the correct folding of T-synthase to form active enzyme. This review will summarize our current understanding of the Tn and STn antigens in terms of their biochemistry and role in pathology.

Synergistic effect of mesangial cell-induced CXCL1 and TGF-β1 in promoting podocyte loss in IgA nephropathy

Podocyte loss has been reported to relate to disease severity and progression in IgA nephropathy (IgAN). However, the underlying mechanism for its role in IgAN remain unclear. Recent evidence has shown that IgA1 complexes from patients with IgAN could activate mesangial cells to induce soluble mediator excretion, and further injure podocytes through mesangial-podocytic cross-talk. In the present study, we explored the underlying mechanism of mesangial cell-induced podocyte loss in IgAN. We found that IgA1 complexes from IgAN patients significantly up-regulated the expression of CXCL1 and TGF-β1 in mesangial cells compared with healthy controls. Significantly higher urinary levels of CXCL1 and TGF-β1 were also observed in patients with IgAN compared to healthy controls. Moreover, IgAN patients with higher urinary CXCL1 and TGF-β1 presented with severe clinical and pathological manifestations, including higher 24-hour urine protein excretion, lower eGFR and higher cresentic glomeruli proportion. Further in vitro experiments showed that increased podocyte death and reduced podocyte adhesion were induced by mesangial cell conditional medium from IgAN (IgAN-HMCM), as well as rhCXCL1 together with rhTGF-β1. In addition, the over-expression of CXCR2, the receptor for CXCL1, by podocytes was induced by IgAN-HMCM and rhTGF-β1, but not by rhCXCL1. Furthermore, the effect of increased podocyte death and reduced podocyte adhesion induced by IgAN-HMCM and rhCXCL1 and rhTGF-β1 was rescued partially by a blocking antibody against CXCR2. Moreover, we observed the expression of CXCR2 in urine exfoliated podocytes in IgAN patients. Our present study implied that IgA1 complexes from IgAN patients could up-regulate the secretion of CXCL1 and TGF-β1 in mesangial cells. Additionally, the synergistic effect of CXCL1 and TGF-β1 further induced podocyte death and adhesion dysfunction in podocytes via CXCR2. This might be a potential mechanism for podocyte loss observed in IgAN.

Clinical characteristics and treatment of patients with IgA nephropathy and hepatitis B surface antigen

BACKGROUND

The aim of this study is to investigate the clinical characteristics and our experience of treating patients with IgA nephropathy (IgAN) and IgA nephropathy with hepatitis B surface antigen (HBs-IgAN).

METHODS

From 1996 to 2011, biopsy-proven IgAN was diagnosed in 477 patients and 22 (4.6%) had hepatitis B surface antigen (HBsAg). Of these, we included 360 patients who had more than 6-month follow-up period, and compared clinical characteristics and renal function decline between the patients with IgAN and HBs-IgAN.

RESULTS

Of 360 patients, 22 were classified as HBs-IgAN. There were no differences in the clinical characteristics and renal function decline between idiopathic IgAN and HBs-IgAN (-0.01 vs. -0.17 mL/min per 1.73 m(2)/month, p = 0.319). Of 22 patients with HBs-IgAN, nine had hepatitis B virus (HBV) replication marker (RM), of which six were treated with anti-viral agents. However, there were no differences in renal function decline and urinary protein excretion between patients who did or did not receive anti-viral therapy. Five patients with HBs-IgAN received corticosteroid therapy. Of these, three without HBV RM and one with HBV RM who received entecavir did not exhibit active viral replication, whereas the other patients with HBV RM experienced viral replication after lamivudine was discontinued.

CONCLUSION

There were no differences in the clinical characteristics and prognosis between the patients with IgAN and HBs-IgAN. Further, there were no differences in renal function decline and urinary protein excretion between patients with and without anti-viral therapy. Anti-viral therapy may be considered for treating patients with HBs-IgAN receiving immunosuppressants according to HBV RM.

The level of galactose-deficient IgA1 in the sera of patients with IgA nephropathy is associated with disease progression

Although high serum levels of galactose-deficient IgA1 (an important biomarker of IgA nephropathy (IgAN)) are found in most patients with IgAN, their relationship to disease severity and progression remains unclear. To help clarify this we prospectively enrolled 275 patients with IgAN and followed them for a median of 47 months (range 12-96 months). Serum galactose-deficient IgA1 was measured at the time of diagnosis using a lectin-based ELISA, and renal survival was modeled using the Cox proportional hazards method. The serum levels of galactose-deficient IgA1 were higher in patients with IgAN compared to those in healthy controls. Importantly, in adjusted analysis, higher levels of galactose-deficient IgA1 were independently associated with a greater risk of deterioration in renal function with a hazard ratio of 1.44 per standard deviation of the natural log-transformed galactose-deficient IgA1 concentration. In reference to the first quartile, the risk of kidney failure increased such that the hazard ratio for the second quartile was 2.47, 3.86 for the third, and 4.76 for the fourth quartile of the galactose-deficient IgA1 concentration. Hence, elevated serum levels of galactose-deficient IgA1 are associated with a poor prognosis in IgAN.

Immunoglobulin A nephropathy associated with Plasmodium falciparum malaria

Glomerulonephritis occurs as a rare form of renal manifestation in Plasmodium falciparum malaria. Herein, we report a case of falciparum malaria-associated IgA nephropathy for the first time. A 49-yr old male who had been to East Africa was diagnosed with Plasmodium falciparum malaria. Microhematuria and proteinuria along with acute kidney injury developed during the course of the disease. Kidney biopsy showed mesangial proliferation and IgA deposits with tubulointerstitial inflammation. Laboratory tests after recovery from malaria showed disappearance of urinary abnormalities and normalization of kidney function. Our findings suggest that malaria infection might be associated with IgA nephropathy.

Glycosylation of IgA1 and pathogenesis of IgA nephropathy

IgA nephropathy, described in 1968 as IgA-IgG immune-complex disease, is an autoimmune disease. Galactose-deficient IgA1 is recognized by unique autoantibodies, resulting in the formation of pathogenic immune complexes that ultimately induce glomerular injury. Thus, formation of the galactose-deficient IgA1-containing immune complexes is a critical factor in the pathogenesis of IgA nephropathy. Studies of molecular defects of IgA1 can define new biomarkers specific for IgA nephropathy that can be developed into clinical assays to aid in the diagnosis, assessment of prognosis, and monitoring of disease progression.

Pathological role of tonsillar B cells in IgA nephropathy

Although impaired immune regulation along the mucosa-bone marrow axis has been postulated to play an important role, the pathogenesis of IgA nephropathy (IgAN) is unknown; thus, no disease-specific therapy for this disease exists. The therapeutic efficacy of tonsillectomy or tonsillectomy in combination with steroid pulse therapy for IgAN has been discussed. Although randomized control trials for these therapies are ongoing in Japan, the scientific rationale for these therapies remains obscure. It is now widely accepted that abnormally glycosylated IgA1 and its related immune complex (IC) are probably key molecules for the pathogenesis, and are thus considered possible noninvasive biomarkers for this disease. Emerging evidence indicates that B cells in mucosal infections, particularly in tonsillitis, may produce the nephritogenic IgA. In this paper, we briefly summarize characteristics of the nephritogenic IgA/IgA IC, responsible B cells, and underlying mechanisms. This clinical and experimental information may provide important clues for a therapeutic rationale.

Hepatitis B virus-associated glomerular nephritis in East Asia: progress and challenges

BACKGROUND

Hepatitis B virus-associated glomerular nephritis (HBV-GN) is the most common secondary glomerulonephritis in East Asia. Part of the patients developed to renal insufficiency within 10 years, which cause a great burden for patients' family and society.

METHODS

We reviewed basic and clinical research work in China, Japan, Korea, and Mongolia, eastern part of Asia. Comparisons between data from East Asia and those from other regions were made.

RESULTS

The genetic variations conferring susceptibility to HBV-GN and disease progression as well as the pathogenic role in HBV-GN progression were investigated. Clinical features of HBV-GN in East Asia were different from that of other regions in the world. Clinical trials showed that treatment with anti-viral agents was effective to promote the disease remission.

CONCLUSION

HBV-GN remains a great challenge to East Asian nephrologists. In-depth basic studies and multi-centered clinical trials are needed in the future.

Idiopathic immunoglobulin A nephropathy in children and adolescents

Immunoglobulin A nephropathy is now recognized as the glomerular disease most often associated with progressive renal failure in patients around the world. In many cases it is not known when the disease starts to inflict glomerular injury, but recent studies that have shown genetically determined abnormalities in glycosylation of the IgA molecule suggest that this may begin in early life. This review focuses on recent advances in our understanding of IgA nephropathy, with special emphasis on clinical aspects of the disease when it presents in children and adolescents. In addition, the sections dealing with therapeutic options for patients with IgA nephropathy concentrate on studies that have been carried out on children. Whenever possible, data from randomized controlled clinical trials have formed the basis for recommendations. Unfortunately, this is not always possible, because of the lack of such trials in patients with IgA nephropathy.

Role of activating transcription factor 3 (ATF3) in sublytic C5b-9-induced glomerular mesangial cell apoptosis

Sublytic complement C5b-9 complexes can cause cell apoptosis, but the mechanism of glomerular mesangial cell (GMC) apoptosis mediated by these complexes has not been well defined. The activating transcription factor 3 (ATF3) gene is an immediate early gene for the cell to cope with a variety of stress signals and can promote apoptosis of some cells. In this study, ATF3 expression and cell apoptosis in GMCs induced by sublytic C5b-9 were measured, and then the effects of ATF3 gene over-expression or knockdown on GMC apoptosis induced by sublytic C5b-9 were examined at a fixed time. The results showed that both ATF3 expression and GMC apoptosis were markedly increased and ATF3 over-expression obviously increased sublytic C5b-9-induced GMC apoptosis, whereas ATF3 gene silencing had a significant opposite effect. Collectively, these findings indicate that upregulation of ATF3 gene expression is involved in regulating GMC apoptosis induced by sublytic C5b-9 complexes.

Differences between juvenile-onset ankylosing spondylitis and adult-onset ankylosing spondylitis

BACKGROUND

Ankylosing spondylitis (AS) is a chronic inflammatory disease, which involves the spine, peripheral joints and entheses. Juvenile-onset ankylosing spondylitis (JAS) affects children under the age of 16 years. JAS has been noted to present as clinical courses different from those of adult-onset ankylosing spondylitis (AAS). Therefore, the purpose of the present study was to compare the possible risk factors, clinical manifestations, laboratory markers, radiological changes, and functional outcome between these 2 patient groups.

METHODS

AS patients were enrolled from the rheumatologic clinic of a tertiary medical center from January 1 to June 30 in 2006. The demographic data, clinical symptoms/signs, Bath AS indices, HLA-B27, inflammatory markers, radiological findings, and treatment history were acquired with questionnaires, clinical evaluation, and chart review. The differences between JAS and AAS patients were evaluated and analyzed.

RESULTS

A total of 169 patients (142 males, 27 females) were included, comprising 47 JAS and 122 AAS patients. The ages of onset were 12.8 +/- 2.7 years and 25.0 +/- 7.4 years for JAS and AAS, respectively. They had similar gender distribution, years of delay to diagnosis and disease duration. A substantial proportion of our patients (40.4% of JAS and 34.4% of AAS) had physical trauma in the 1 month before disease onset. Also, 22.7% of JAS patients had intense physical training, while 25.2% of AAS patients did heavy work during the period. The first manifestation of JAS was mainly peripheral enthesopathy or arthritis, but axial symptoms in most AAS. More JAS patients had peripheral enthesopathies and arthritis on any occasion. Although there was a trend of higher score in Bath AS Disease Activity Index (BASDAI), Bath AS Metrology Index (BASMI) and Physician's Global Assessment (PGA) score, JAS patients had a comparable Bath AS Functional Index (BASFI) and Bath AS Patient's Global Assessment (BAS-G) as AAS patients. As to the laboratory and radiological tests, JAS patients had higher levels of C-reactive protein and erythrocyte sedimentation rate, and more radiographic changes of hip joints.

CONCLUSION

JAS and AAS patients had distinct presentations. JAS presented more peripheral enthesopathies and arthritis at disease onset and at any time of the course. If treated effectively, JAS will not lead to a worse functional outcome than AAS. Therefore, it is mandatory to diagnose and treat JAS as early as possible.

Apoptosis of glomerular mesangial cells induced by sublytic C5b-9 complexes in rats with Thy-1 nephritis is dependent on Gadd45 gamma upregulation

The complement C5b-9 complexes can result in cell apoptosis, but the mechanism of sublytic C5b-9-mediated glomerular mesangial cell (GMC) apoptosis in Thy-1 nephritis (Thy-1N) remains largely unclear. The Gadd45 gene is involved in the cellular response to DNA damage and can promote cell apoptosis. In this study, both Gadd45 gamma expression patterns and pathologic changes of renal tissue were examined in rat Thy-1N. Both Gadd45 gamma expression and GMC apoptosis were significantly decreased in Thy-1N rats upon the depletion of complement with cobra venom factor. Our in vitro studies showed that Gadd45 gamma over-expression increased sublytic C5b-9-induced GMC apoptosis, while Gadd45 gamma gene knockdown by siRNA greatly reduced GMC apoptosis. Moreover, Gadd45 gamma gene silencing in vivo markedly inhibited the pathologic changes in the renal tissue of Thy-1N rats. These data suggest that Gadd45 gamma gene expression is involved in regulating GMC apoptosis mediated by sublytic C5b-9 in Thy-1N.

Mucin-type O-glycans in tears of normal subjects and patients with non-Sjögren's dry eye

PURPOSE

O-linked carbohydrates (O-glycans) contribute to the hydrophilic character of mucins in mucosal tissues. This study was conducted to identify the repertoire of O-glycans in the tear film and the glycosyltransferases associated with their biosynthesis, in normal subjects and patients with non-Sjögren's dry eye.

METHODS

Human tear fluid was collected from the inferior conjunctival fornix. O-glycans were released by hydrazinolysis, labeled with 2-aminobenzamide, and analyzed by fluorometric, high-performance liquid chromatography (HPLC) coupled with exoglycosidase digestions. O-glycan structures identified in tears were related to potential biosynthetic pathways in human conjunctival epithelium by using a glycogene microarray database. Lectin-binding analyses were performed with agglutinins from Arachis hypogaea, Maackia amurensis, and Sambucus nigra.

RESULTS

The O-glycan profile of human tears consisted primarily of core 1 (Gal beta 1-3GalNAc alpha 1-Ser/Thr)-based structures. Mono-sialyl O-glycans represented approximately 66% of the glycan pool, with alpha2-6-sialyl core 1 being the predominant O-glycan structure in human tears (48%). Four families of glycosyltransferases potentially related to the biosynthesis of these structures were identified in human conjunctiva. These included 13 polypeptide-GalNAc-transferases (GALNT), the core 1 beta-3-galactosyltransferase (T-synthase), three alpha2-6-sialyltransferases (ST6GalNAc), and two alpha2-3-sialyltransferases (ST3Gal). No significant differences in total amount of O-glycans were detected between tears of normal subjects and patients with dry eye, by HPLC and lectin blot. Likewise, no differences in glycosyltransferase expression were found by glycogene microarray.

CONCLUSIONS

This study identified the most common mucin-type O-glycans in human tears and their expected biosynthetic pathways in ocular surface epithelia. Patients with non-Sjögren's dry eye showed no alterations in composition and amount of O-glycans in the tear fluid.