Serum levels of galactose-deficient IgA in children with IgA nephropathy and Henoch-Schönlein purpura

Insight into the Interplay of Gd-IgA1, HMGB1, RAGE and PCDH1 in IgA Vasculitis (IgAV)

The pathogenesis of IgAV, the most common systemic vasculitis in childhood, appears to be complex and requires further elucidation. We aimed to investigate the potential role of galactose-deficient immunoglobulin A1 (Gd-IgA1), high-mobility group box 1 (HMGB1), receptor for advanced glycation end products (RAGE) and protocadherin 1 (PCDH1) in the pathogenesis of IgAV. Our prospective study enrolled 86 patients with IgAV and 70 controls. HMGB1, RAGE, Gd-IgA1 and PCDH1 in serum and urine were determined by the enzyme-linked immunosorbent assay (ELISA) method at the onset of the disease and after a six-month interval in patients and once in the control group. Serum concentrations of HMGB1, RAGE and PCDH1 and urinary concentrations of HMGB1, RAGE, Gd-IgA1 and PCDH1 were significantly higher in patients with IgAV than in the control group (p < 0.001). Concentrations of HMGB1 (5573 pg/mL vs. 3477 pg/mL vs. 1088 pg/mL, p < 0.001) and RAGE (309 pg/mL vs. 302.4 pg/mL vs. 201.3 pg/mL, p = 0.012) in the serum of patients remained significantly elevated when the disease onset was compared with the six-month follow-up interval, and thus could be a potential marker of disease activity. Urinary concentration of HMGB1 measured in the follow-up period was higher in patients with nephritis compared to IgAV without nephritis (270.9 (146.7-542.7) ng/mmol vs. 133.2 (85.9-318.6) ng/mmol, p = 0.049) and significantly positively correlated with the urine albumine to creatinine ratio (τ = 0.184, p < 0.05), the number of erythrocytes in urine samples (τ = 0.193, p < 0.05) and with the outcome of nephritis (τ = 0.287, p < 0.05); therefore, HMGB1 could be a potential tool for monitoring patients with IgAV who develop nephritis. Taken together, our results imply a possible interplay of Gd-IgA1, HMGB1, RAGE and PCDH1 in the development of IgAV. The identification of sensitive biomarkers in IgAV may provide disease prevention and future therapeutics.

Hydroxychloroquine Induces Remission for IgA Nephropathy With Mild to Moderate Proteinuria: A Single-Centered Retrospective Analysis

BACKGROUND

Hydroxychloroquine (HCQ) influences both toll-like receptor (TLR) signaling and leukocyte activation, which are speculated to play a role in the pathogenesis of IgA nephropathy (IgAN).

METHODS

This is a single-centered retrospective study involving 426 IgAN patients diagnosed from May 2016 to August 2020. All patients were matched according to a propensity score matching (PSM) to produce three groups: renin-angiotensin-aldosterone system inhibitors (RAASi) group (RAASi only), corticosteroids group (corticosteroids only or combined with RAASi), and HCQ group (HCQ only or combined with RAASi), consisting of 63 patients for each group.

RESULTS

After PSM, the median urine protein/creatinine ratio (UPCR) of overall patients was 0.91 g/g, while their median serum creatinine was 87.00 μmol/L. After the median follow-up period of 11.03 months, the total remission rates of the RAASi group, corticosteroids group, and HCQ groups were 49.21% (n = 31), 74.60% (n = 47), and 52.38% (n = 33), respectively (p = 0.017). Thirteen (6.88%) patients experienced a decline in estimated glomerular filtration rate (eGFR) of more than 25% from baseline, including six (9.52%) patients in the RAASi group, three (4.76%) patients in the corticosteroids group, and four (6.35%) patients in HCQ group (p = 0.677). One (1.59%) patient in the HCQ group had blurred vision and continued to use HCQ after ruling out retinal lesions by ophthalmic examination.

CONCLUSION

HCQ is effective in inducing remission and well-tolerated in IgAN patients with mild to moderate proteinuria.

Immunoglobulin A vasculitis nephritis: Current understanding of pathogenesis and treatment

The clinical spectrum of immunoglobulin A vasculitis nephritis (IgAVN) ranges from the relatively common transitory microscopic hematuria and/or low-grade proteinuria to nephritic or nephrotic syndrome, rapidly progressive glomerulonephritis, or even renal failure. Clinical and experimental studies have shown a multifactor pathogenesis: Infection triggers, impaired glycosylation of IgA1, complement activation, Toll-like-receptor activation and B cell proliferation. This knowledge can identify IgAVN patients at a greater risk for adverse outcome and increase the evidence for treatment recommendations.

Glomerulonephritis

Glomerulonephritis (GN) encompasses several disorders that cause glomerular inflammation and injury through an interplay of immune-mediated mechanisms, host characteristics, and environmental triggers, such as infections. GN can manifest solely in the kidney or in the setting of a systemic illness, and presentation can range from chronic and relatively asymptomatic hematuria to fulminant renal failure. Classic acute GN is characterized by hematuria, edema, and hypertension, the latter 2 of which are the consequence of sodium and water retention in the setting of renal impairment. Although presenting signs and symptoms and a compatible clinical history can suggest GN, serologic and urinary testing can further refine the differential diagnosis, and renal biopsy can be used for definitive diagnosis. Treatment of GN can include supportive care, renin-angiotensin-aldosterone system blockade, immunomodulatory therapy, and renal transplant. Prognosis is largely dependent on the underlying cause of GN and can vary from a self-limited course to chronic kidney disease. This review focuses on lupus nephritis, IgA nephropathy, IgA vasculitis, and postinfectious GN.

IgA Nephropathy: Pleiotropic impact of Epstein-Barr virus infection on immunopathogenesis and racial incidence of the disease

IgA nephropathy (IgAN) is an autoimmune disease in which poorly galactosylated IgA1 is the antigen recognized by naturally occurring anti-glycan antibodies, leading to formation of nephritogenic circulating immune complexes. Incidence of IgAN displays geographical and racial disparity: common in Europe, North America, Australia, and east Asia, uncommon in African Americans, many Asian and South American countries, Australian Aborigines, and rare in central Africa. In analyses of sera and cells from White IgAN patients, healthy controls, and African Americans, IgAN patients exhibited substantial enrichment for IgA-expressing B cells infected with Epstein-Barr virus (EBV), leading to enhanced production of poorly galactosylated IgA1. Disparities in incidence of IgAN may reflect a previously disregarded difference in the maturation of the IgA system as related to the timing of EBV infection. Compared with populations with higher incidences of IgAN, African Americans, African Blacks, and Australian Aborigines are more frequently infected with EBV during the first 1-2 years of life at the time of naturally occurring IgA deficiency when IgA cells are less numerous than in late childhood or adolescence. Therefore, in very young children EBV enters "non-IgA" cells. Ensuing immune responses prevent infection of IgA B cells during later exposure to EBV at older ages. Our data implicate EBV-infected cells as the source of poorly galactosylated IgA1 in circulating immune complexes and glomerular deposits in patients with IgAN. Thus, temporal differences in EBV primo-infection as related to naturally delayed maturation of the IgA system may contribute to geographic and racial variations in incidence of IgAN.

Pathophysiology and clinical manifestations of immune complex vasculitides

Immune complex (IC) vasculitides present inflammations of vessel walls associated with perivascular deposition of immunoglobulins (Igs), mostly ICs. They encompass systemic and skin-limited variants of IgA vasculitis (IgAV), cryoglobulinemic vasculitis (CV), rheumatoid, lupus, and hypocomplementemic vasculitides, serum sickness cutaneous IgM/IgG (non-IgA) vasculitis, and recurrent macular (hypergammaglobulinemic or exertion-induced) vasculitis. Serum sickness and CV fulfill the criteria of a type III hypersensitivity immune reaction as large lattices of the IC precipitate at vessel walls and activate polymorphonuclear neutrophils (PMNs). Immunoglobulin-A vasculitis differs with regard to the causes of perivascular deposition of ICs since here many IgA1 molecules are hypoglycosylated (Gd-IgA1), which appears to facilitate their perivascular deposition in skin and mesangium (via e.g. CD71). The reasons for increased generation of immunoglobulins or formation of IC and their perivascular deposition in either skin or systemic organs are different and not fully explored. A common denominator of OC vasculitides is the activation of PMNs near the vessel wall via Fcy or Fcα receptors. Acute episodes of IgAV additionally require PMNs to become preactivated by IgA1 or by IC already in circulation. This intravascular priming results in increased adherence and subsequently vessel-destructive NETosis when they encounter IgA deposited at the vessel walls. Binding of IgA1 to PMNs in blood stream is associated with increased serum levels of hypogalactosidated IgA1. The characteristic clinical picture of IgAV (and also of so-called IgG/IgM vasculitis) comprises palpable or retiform purpura with a clear predilection for lower legs, probably due to stasis-related reduction in blood velocity, while in other IC vasculitides, additional factors influence the sites of vasculitides. Our knowledge of distinct forms and different pathophysiological pathways of IC vasculitides may lead to in efficacious or targeted therapies. Antibodies to complement components or intestinal budesonide for IgAV are promising agents (the latter suppresses the pathophysiologically related IgA nephropathy by reducing the generation of mucosal IgA.

IgA Vasculitis With Adalimumab Therapy for Hidradenitis Suppurativa: A Case Report and Review of Literature

Immunoglobulin A (IgA) vasculitis is a systemic vasculitis characterized by inflammation of the small vessels, with cutaneous, musculoskeletal, gastrointestinal, and renal involvement, usually seen in pediatric populations. Hidradenitis suppurativa is a chronic inflammatory disorder of the skin, which can be treated by tumor necrosis factor-α (TNFα) inhibitor therapy. TNFα inhibitor therapy is used as an important milestone in the treatment of various rheumatological and autoimmune disorders. Unexpected adverse effects might occur. However, they are usually mild and do not warrant treatment withdrawal. We present a case of IgA vasculitis complicating adalimumab therapy for hidradenitis suppurativa. We also review and discuss similar cases reported in the literature.

Bibliometric analysis of IgA vasculitis nephritis in children from 2000 to 2022

Background

IgA vasculitis Nephritis (IgAVN) is a kidney-damaging disease that occurs during the course of IgA vasculitis (IgAV) and is the most serious complication of IgAV. However, there is a lack of reports of bibliometric analysis of IgAVN in children. The purpose of this study is to conduct a bibliometric analysis of IgAVN in children from 2000 to 2022, to explore the current status and cutting-edge trends in the field of IgAVN in children, and to establish new directions for subsequent research.

Methods

Screening the literature in the field of IgAVN in children in the Web of Science Core Collection (WoSCC) from 2000 to 2022. Visual analysis of their annual publications, countries, institutions, authors, journals, keywords, and references were using CiteSpace5.8.R3 and VOSviewer1.6.18.

Results

A total of 623 publications were included in the study, since the beginning of 2014, there has been an overall increasing trend in the number of articles issued. The most prolific country and institution were China and Zhejiang University. The most frequently cited author was Coppo R, with 331 citations, who has made great contributions to IgAVN. Mao Jianhua, Lee JS and Wyatt Robert J were the most prolific authors, all with 9 articles. Pediatric Nephrology was the most published and cited journal. The highest burst strength keyword is IgA vasculitis, and the highest burst strength reference is Davin JC, 2014.

Conclusion

The research hotspots and trends predicted by the analysis of this study provide a reference for in-depth research in this field with a view to promoting the development of IgAVN research in children.

Time of Onset and Risk Factors of Renal Involvement in Children with Henoch-Schönlein Purpura: Retrospective Study

Background: Henoch-Schönlein purpura (HSP) is a common systemic vasculitis in children, involving the skin, musculoskeletal system, gastrointestinal tract and kidneys. Some studies in children have shown possible risk factors linked with the development and severity of HSP Nephritis (HSPN). The aim of this study was to research predicting factors for the development of HSPN. Methods: We retrospectively evaluated 132 pediatric patients with HSP, according to EULAR/PRINTO/PRESS criteria. All patients were screened for HSPN by urinalysis. Finally, we compared demographic, clinical and laboratory data in HSP patients with and without nephritis. Results: The median age at HSP diagnosis [6.2 (2.6–17.5) vs. 5.5 (0.8–15.4) years, p = 0.03] and the incidence of abdominal pain (48 vs. 27%, p = 0.01) were significantly higher in HSPN patients. No differences were evidenced regarding gender, allergic diseases, skin recurrences, gastrointestinal involvement, musculoskeletal involvement, scrotal involvement, and laboratory data (white blood cell count, neutrophil count, lymphocyte count, platelet count, C-reactive protein, erythrocyte sedimentation rate, and blood concentration of IgA). Conclusions: The age at diagnosis and abdominal pain were independent risk factors for renal involvement in HSP patients. However, due to the retrospective nature of this study, further long-term and prospective studies will be necessary.

IgA vasculitis with nephritis: update of pathogenesis with clinical implications

IgA vasculitis with nephritis (IgAVN) shares many pathogenetic features with IgA nephropathy (IgAN). The purpose of this review is to describe our current understanding of the pathogenesis of pediatric IgAVN, particularly as it relates to the four-hit hypothesis for IgAN. These individual steps, i.e., hits, in the pathogenesis of IgAN are (1) elevated production of IgA1 glycoforms with some O-glycans deficient in galactose (galactose-deficient IgA1; Gd-IgA1), (2) generation of circulating IgG autoantibodies specific for Gd-IgA1, (3) formation of pathogenic circulating Gd-IgA1-containing immune complexes, and (4) kidney deposition of the Gd-IgA1-IgG immune complexes from the circulation and induction of glomerular injury. Evidence supporting the four-hit hypothesis in the pathogenesis of pediatric IgAVN is detailed. The genetics, pediatric outcomes, and kidney histopathologic features and the impact of these findings on future treatment and potential biomarkers are discussed. In summary, the evidence points to the critical roles of Gd-IgA1-IgG immune complexes and complement activation in the pathogenesis of IgAVN. Future studies are needed to characterize the features of the immune and autoimmune responses that enable progression of IgA vasculitis to IgAVN.

Treatment strategy with multidrug therapy and tonsillectomy pulse therapy for childhood-onset severe IgA nephropathy

BACKGROUND

IgA nephropathy is a typical chronic glomerulonephritis that tends to occur in childhood.

METHOD

We reviewed the report on pathogenesis, treatment strategy with multidrug therapy and tonsillectomy pulse therapy for childhood-onset severe IgA nephropathy to clarify the pathophysiology and treatment of IgA nephropathy in childhood.

RESULTS

In recent years, it has been found that the pathogenesis at onset is associated with aberrant glycosylation at the IgA1 hinge. Given this genetic background, the aberrantly glycosylated IgA1immune complex produced by antigen-stimulated T cells and B cells is deposited in the glomeruli. Inflammation is induced via activation of the complement, macrophages and mesangial cells, and glomerular damage progresses thereafter. Treatment is selected according to the severity of IgA nephropathy. In order to prevent the development of renal damage, it is important to control the associated immune responses. For severe IgA nephropathy, in particular, multidrug therapy with prednisolone, immunosuppressants, and angiotensin enzyme synthesis inhibitors and tonsillectomy methylprednisolone pulse therapy are now performed- and, as a result, the number of renal deaths has decreased and the long-term prognosis has improved.

CONCLUSION

The prognosis of IgA nephropathy is improving. In the future, it will be important to develop a treatment method that takes into consideration the fact that children are in their growth and development stage and, therefore, seeks to minimizes side effects.

IgA Vasculitis with Nephritis in Adults: Histological and Clinical Assessment

Patients with IgA vasculitis (IgAV), an immune complex-mediated disease, may exhibit kidney involvement-IgAV with nephritis (IgAVN). The kidney-biopsy histopathologic features of IgAVN are similar to those of IgA nephropathy, but little is known about histopathologic disease severity based on the interval between purpura onset and diagnostic kidney biopsy. We assessed kidney histopathology and clinical and laboratory data in a cohort of adult patients with IgAVN (n = 110). The cases were grouped based on the interval between the onset of purpura and kidney biopsy: Group 1 (G1, <1 month, n = 14), Group 2 (G2, 1-6 months, n = 58), and Group 3 (G3, >6 months, n = 38). Glomerular leukocytes were more common in G1 than in the other groups (p = 0.0008). The proportion of neutrophils among peripheral-blood leukocytes was the highest in the patients biopsied within a month after onset of purpura (G1: 71 ± 8%). In the patients with an interval >6 months, the neutrophil proportion was lower, 60%. Moreover, the glomerular mesangial proliferation score correlated with the serum total IgA concentration (p = 0.0056). In conclusion, IgAVN patients biopsied <1 month from purpura onset showed an elevated percentage of blood neutrophils and glomerular leukocytes, consistent with an acute-onset inflammatory reaction. In all IgAVN patients, the mesangial proliferation score correlated with the serum IgA level.

IgA Vasculitis: Etiology, Treatment, Biomarkers and Epigenetic Changes

IgA, previously called Henoch-Schönlein vasculitis, is an essential immune component that drives the host immune response to the external environment. As IgA has the unique characteristic of a flexible response to broad types of microorganisms, it sometimes causes an autoreactive response in the host human body. IgA vasculitis and related organ dysfunction are representative IgA-mediated autoimmune diseases; bacterial and viral infections often trigger IgA vasculitis. Recent drug developments and the presence of COVID-19 have revealed that these agents can also trigger IgA vasculitis. These findings provide a novel understanding of the pathogenesis of IgA vasculitis. In this review, we focus on the characteristics of IgA and symptoms of IgA vasculitis and other organ dysfunction. We also mention the therapeutic approach, biomarkers, novel triggers for IgA vasculitis, and epigenetic modifications in patients with IgA vasculitis.

IgA Vasculitis and IgA Nephropathy: Same Disease?

Many authors suggested that IgA Vasculitis (IgAV) and IgA Nephropathy (IgAN) would be two clinical manifestations of the same disease; in particular, that IgAV would be the systemic form of the IgAN. A limited number of studies have included sufficient children or adults with IgAN or IgAV (with or without nephropathy) and followed long enough to conclude on differences or similarities in terms of clinical, biological or histological presentation, physiopathology, genetics or prognosis. All therapeutic trials available on IgAN excluded patients with vasculitis. IgAV and IgAN could represent different extremities of a continuous spectrum of the same disease. Due to skin rash, patients with IgAV are diagnosed precociously. Conversely, because of the absence of any clinical signs, a renal biopsy is practiced for patients with an IgAN to confirm nephropathy at any time of the evolution of the disease, which could explain the frequent chronic lesions at diagnosis. Nevertheless, the question that remains unsolved is why do patients with IgAN not have skin lesions and some patients with IgAV not have nephropathy? Larger clinical studies are needed, including both diseases, with a common histological classification, and stratified on age and genetic background to assess renal prognosis and therapeutic strategies.

Immunoglobulin A Glycosylation and Its Role in Disease

Human IgA is comprised of two subclasses, IgA1 and IgA2. Monomeric IgA (mIgA), polymeric IgA (pIgA), and secretory IgA (SIgA) are the main molecular forms of IgA. The production of IgA rivals all other immunoglobulin isotypes. The large quantities of IgA reflect the fundamental roles it plays in immune defense, protecting vulnerable mucosal surfaces against invading pathogens. SIgA dominates mucosal surfaces, whereas IgA in circulation is predominately monomeric. All forms of IgA are glycosylated, and the glycans significantly influence its various roles, including antigen binding and the antibody effector functions, mediated by the Fab and Fc portions, respectively. In contrast to its protective role, the aberrant glycosylation of IgA1 has been implicated in the pathogenesis of autoimmune diseases, such as IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN). Furthermore, detailed characterization of IgA glycosylation, including its diverse range of heterogeneity, is of emerging interest. We provide an overview of the glycosylation observed for each subclass and molecular form of IgA as well as the range of heterogeneity for each site of glycosylation. In many ways, the role of IgA glycosylation is in its early stages of being elucidated. This chapter provides an overview of the current knowledge and research directions.

Serum levels of galactose-deficient IgA1 in Chinese children with IgA nephropathy, IgA vasculitis with nephritis, and IgA vasculitis

OBJECTIVE

IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAV-N) are related diseases. Galactose-deficient IgA1 (Gd-IgA1) plays an important role in the pathology of IgAV-N and IgAN, so we aim to compare the serum levels of Gd-IgA1 in Chinese pediatric patients with IgAN, IgAV-N, and IgAV.

METHODS

We retrospectively enrolled 52 patients with IgAN, 57 patients with IgAV-N, 26 patients with IgAV, and 40 healthy children. The serum levels of Gd-IgA1 were measured at the time of biopsy using a lectin-based ELISA method.

RESULTS

Gd-IgA1 levels in IgAV-N patients and IgAN patients were higher than in healthy controls (303.94 ± 39.37 U/ml, 314.91 ± 47.79 U/ml vs. 273.57 ± 48.29 U/ml, P < 0.001), and Gd-IgA1 levels in IgAV-N patients were higher than in IgAV patients (303.94 ± 39/ml vs. 286. 21 ± 38.81 U/ml, P = 0.059), but the latter result is not statistically significant. The Gd-IgA1 levels in IgAV patients were comparable with those in healthy controls (286.21 ± 38.81 U/ml vs. 273.57 ± 48.29 U/ml, P = 0.267). Among the four groups, we did not observe significant correlations of Gd-IgA1 levels with eGFR, proteinuria, or the MEST-C score.

CONCLUSION

Serum Gd-IgA1 maybe involved in the pathogenesis of the IgAV-N and IgAN. However, we found no statistically significant correlation between Gd-IgA1 levels and clinical and pathological features.

Glomerular galactose-deficient IgA1 expression analysis in pediatric patients with glomerular diseases

Galactose-deficient IgA1 (Gd-IgA1) is important in the pathogenesis of IgA nephropathy (IgAN). A Gd-IgA1-specific monoclonal antibody (KM55) has revealed glomerular Gd-IgA1 deposition solely in patients with IgAN and IgA vasculitis with nephritis (IgAV-N). However, this specificity is controversial and has not been demonstrated in pediatric patients. Here, we conducted double-immunofluorescence staining of IgA and Gd-IgA1 in 60 pediatric patients with various glomerular diseases. We divided patients into four groups: (1) patients with IgAN and IgAV-N (n = 23); (2) patients with immunocomplex-mediated glomerulonephritis accompanied by IgA deposition, including lupus nephritis, membranoproliferative glomerulonephritis, and membranous nephropathy (n = 14); (3) patients with other glomerular diseases involving IgA deposition, including idiopathic nephrotic syndrome (INS), oligomeganephronia, Alport syndrome, dense deposit disease, and crescentic glomerulonephritis (n = 11); and (4) patients with IgA-negative diseases including INS, membranoproliferative glomerulonephritis, membranous nephropathy, oligomeganephronia, Alport syndrome, C3 glomerulonephritis, poststreptococcal acute glomerulonephritis, and hemolytic uremic syndrome (n = 12). KM55 staining revealed Gd-IgA1-positive findings in 23/23 patients in Group 1 and 13/14 patients in Group 2, but not in patients in Groups 3 or 4. Therefore, KM55 may detect incidental IgA deposition in pediatric patients. Gd-IgA1 may be involved in the pathogenesis of these immune-related diseases; alternatively, KM55 may recognize IgA-related immunocomplexes in a non-specific manner.

Adult-onset IgA vasculitis (Henoch-Schönlein): Update on therapy

Immunoglobulin A vasculitis (IgAV, formerly Henoch-Schönlein purpura) is a systemic inflammatory disease affecting small vessels. While it is common and usually benign in childhood, in adults it is rarer has a more severe course. Its main manifestations are cutaneous purpura, arthralgias or arthritis, acute enteritis and glomerulonephritis. Renal involvement is associated with a poor prognosis in adults. The treatment of adult-onset IgAV is still a matter of debate: although in patients with a non-severe phenotype remission can occur spontaneously, more severe cases may need immunosuppressive therapy. There are some areas of uncertainty with respect to the efficacy of immunosuppressive regimens: almost all data come from studies performed in children or from patients with IgA nephropathy and/or IgA-crescentic glomerulonephritis. The only randomised study performed in adults with IgAV and renal involvement showed that immunosuppressive therapy with cyclophosphamide did not improve renal outcome nor did it affect patient survival. The possible efficacy of other drugs is reported only in small case series. Recent evidences show that rituximab could be an effective therapeutic option for adult-onset IgAV, but this also needs to be confirmed in controlled trials. In this review, we focus on therapeutic options for adult-onset IgAV treatment, and discuss the main results of the studies performed so far.

Role of Epstein-Barr Virus in Pathogenesis and Racial Distribution of IgA Nephropathy

IgA nephropathy (IgAN) is the dominant type of primary glomerulonephritis worldwide. However, IgAN rarely affects African Blacks and is uncommon in African Americans. Polymeric IgA1 with galactose-deficient hinge-region glycans is recognized as auto-antigen by glycan-specific antibodies, leading to formation of circulating immune complexes with nephritogenic consequences. Because human B cells infected in vitro with Epstein-Barr virus (EBV) secrete galactose-deficient IgA1, we examined peripheral blood B cells from adult IgAN patients, and relevant controls, for the presence of EBV and their phenotypic markers. We found that IgAN patients had more lymphoblasts/plasmablasts that were surface-positive for IgA, infected with EBV, and displayed increased expression of homing receptors for targeting the upper respiratory tract. Upon polyclonal stimulation, these cells produced more galactose-deficient IgA1 than did cells from healthy controls. Unexpectedly, in healthy African Americans, EBV was detected preferentially in surface IgM- and IgD-positive cells. Importantly, most African Blacks and African Americans acquire EBV within 2 years of birth. At that time, the IgA system is naturally deficient, manifested as low serum IgA levels and few IgA-producing cells. Consequently, EBV infects cells secreting immunoglobulins other than IgA. Our novel data implicate Epstein-Barr virus infected IgA⁺ cells as the source of galactose-deficient IgA1 and basis for expression of relevant homing receptors. Moreover, the temporal sequence of racial-specific differences in Epstein-Barr virus infection as related to the naturally delayed maturation of the IgA system explains the racial disparity in the prevalence of IgAN.

Autoantibodies Specific for Galactose-Deficient IgA1 in IgA Vasculitis With Nephritis

Introduction

Patients with IgA nephropathy (IgAN) have elevated serum levels of galactose-deficient IgA1 (Gd-IgA1) that are bound by Gd-IgA1–specific autoantibodies in pathogenic immune complexes. Renal biopsy histopathologic features of IgA vasculitis (IgAV) with nephritis (IgAV-N) are similar to those of IgAN. Mucosal infections often are associated with clinical onset and exacerbation in both diseases. We investigated whether patients with IgAV-N share pathogenic characteristics of IgAN.

Methods

We generated IgA1- and IgG-secreting cell lines from Epstein-Barr virus (EBV)–immortalized cells of patients with IgAV without nephritis (IgAV-woN), IgAV-N, and IgAN and from healthy individuals. Sera and cell-culture supernatants were used for analysis of Gd-IgA1 and Gd-IgA1–specific IgG autoantibodies.

Results

IgA1-producing cells from patients with IgAV-N, like cells from patients with IgAN, secreted more Gd-IgA1 than did cells from patients with IgAV-woN or healthy control subjects, in agreement with elevated serum Gd-IgA1 levels in patients with IgAV-N and IgAN. IgA1-producing cells from patients with IgAV-N had altered expression of genes involved in O-glycan biosynthesis: decreased for core 1 synthase (glycoprotein-N-acetylgalactosamine 3-β-galactosyltransferase 1; C1GALT1) and C1GALT1 Specific Chaperone 1 (C1GALTC1; COSMC) and elevated for N-acetylgalactosaminide α-2,6-sialyltransferase 2 (ST6GALNAC2). Levels of Gd-IgA1–specific IgG in sera and supernatants of IgG-producing cells were similar for patients with IgAV-N and IgAN and higher than those for IgAV-woN patients or healthy control subjects. Moreover, patients with IgAV-N who had active disease, manifested by hematuria and substantial proteinuria, had higher serum levels of Gd-IgA1–specific IgG autoantibodies than did patients with IgAV-N who had inactive disease.

Conclusion

Serum levels and cellular production of Gd-IgA1 and Gd-IgA1–specific IgG autoantibodies were elevated in patients with IgAV-N, supporting the hypothesis that IgAV-N and IgAN share pathogenic features.

Plasma galactose-deficient immunoglobulin A1 and loss of kidney function in patients with immunoglobulin A vasculitis nephritis

Background

Immunoglobulin A (IgA) vasculitis nephritis (IgAV-N) is the most common secondary IgA nephropathy (IgAN). Many studies have demonstrated that galactose-deficient IgA1 (Gd-IgA1) in the IgA1 hinge region is associated with the development and also progression of primary IgAN. In this study, we aimed to evaluate the roles of Gd-IgA1 in kidney disease progression in a large Chinese cohort of IgAV-N patients.

Methods

This cohort study enrolled 112 patients with IgAV-N, 15 patients with IgA vasculitis (IgAV) without kidney involvement and 108 patients with IgAN. Plasma IgA1 and Gd-IgA1 levels at kidney biopsy were measured by enzyme-linked immunosorbent assay. The primary endpoint was a 30% decline in estimated glomerular filtration rate or end-stage renal disease or death.

Results

The levels of Gd-IgA1 in IgAV-N and IgAN patients were higher than in healthy controls (mean ± SD, 302.86 ± 54.93 U/mL versus 303.16 ± 59.43 U/mL versus 281.30 ± 43.74 U/mL, respectively; P = 0.047), as well as compared with those with IgAV without kidney involvement (272.65 ± 53.14 U/mL; P = 0.036). After adjusting clinical data, higher levels of Gd-IgA1 were found to be independently associated with a greater risk for kidney failure [hazard ratio (HR) = 1.703 per 1 SD, 95% confidence interval (CI) 1.233–2.352; P = 0.001]. Compared with the first Gd-IgA1 quartile group (as reference), the fourth Gd-IgA1 quartile group retained a predictive value for poor renal outcome (HR = 3.740, 95% CI 1.204–11.619; P = 0.023).

Conclusions

These data indicate that Gd-IgA1 levels were similarly elevated in adult patients with IgAN and those with IgAV-N. Moreover, increased Gd-IgA1 levels were associated with both the development and progression of IgAV-N, as observed in IgAN.

Do practical laboratory indices predict the outcomes of children with Henoch-Schönlein purpura?

Objectives: Henoch Schönlein Purpura (HSP) is the most common systemic vasculitis of childhood and often has a self-limiting course. We aimed to study whether practical laboratory parameters at the diagnosis predict disease course including recurrence and nephritis in addition to severe gastrointestinal involvement in children with HSP. Methods: This retrospective cohort study included 214 HSP patients, 43.5% (n = 93) female and 56.5% (n =121) male, who were diagnosed in our department. Laboratory parameters before treatment, including neutrophil, lymphocyte and platelet counts, mean platelet volume (MPV), neutrophil-to-lymphocyte (NLR), and platelet-to-lymphocyte ratios (PLR) were obtained retrospectively. Age at diagnosis, duration of follow-up, gender, preceding infections, medications, arthritis and arthralgia, abdominal pain, severe GI involvement, invagination, renal involvement and presence of nephritis, outcomes, and presence of recurrences were retrospectively recorded from medical files. Severe GI involvement was determined as severe colicky abdominal pain, bowel edema in ultrasonography or overt GI bleeding. A relapse was defined as a new flare of cutaneous lesions or other manifestations in a patient at least four asymptomatic weeks after the initial HSP episode. Results: Mean age at diagnosis was 7.6 ± 3.1 years. Biopsy-proven nephritis was found in 16 (7.5%) patients. Severe GI involvement was present in 77 (36%) patients, whereas only 12 (5.6%) patients were diagnosed with intussusception and in 29 (13.5%) patients, HSP recurred. Neutrophil count and NLR were found higher in HSP patients with severe gastrointestinal involvement and biopsy-proven nephritis. Additionally, only platelet count was lower and MPV was higher in patients with recurrent HSP. Conclusion: Elevated neutrophil count and NLR may be relevant markers for severe GI involvement and nephritis, whereas platelet count and MPV were the only laboratory parameters associated with disease recurrence.

Genetic Determinants of IgA Nephropathy: Western Perspective

IgA nephropathy (IgAN) represents a genetically complex multifactorial trait. Its prevalence and clinical features vary geographically, and the disease has a range of clinical presentations that suggest multiple subtypes. Although familial aggregation of IgAN has been reported and prior linkage studies have highlighted significant locus heterogeneity, specific genetic variants underlying familial IgAN have not yet been defined. Population-based genome-wide association studies (GWAS) have discovered nearly 20 IgAN risk loci, providing novel insights into disease epidemiology and molecular mechanisms, shifting old paradigms of the disease pathogenesis. Follow-up fine-mapping studies have identified specific causal variants, and genotype-phenotype correlation studies have begun to delineate clinical consequences of GWAS risk alleles. The association between IgAN and galactose-deficient IgA1 (Gd-IgA1), a validated serum biomarker of IgAN, presented another avenue for genetic discovery because elevated serum levels of Gd-IgA1 are highly heritable. Recent GWAS for serum Gd-IgA1 levels provided novel insights into genetic regulation of this trait, but the genetic link between Gd-IgA1 and IgAN has not yet been established. In this review, we discuss these developments in the broader context of modern genetic approaches to complex traits, and provide our perspective on the critical challenges that need to be addressed to advance the field.

Adult IgA vasculitis (Henoch-Schönlein purpura)

IgA vasculitis is a systemic vasculitis affecting small vessels. IgA vasculitis usually affect children whereas it is rare in adults (150 to 200 for 1) in which the disease is often more serious with more frequent and severe nephritis. Prevalence of adult IgA vasculitis is unknown and its annual incidence is 1 in 1 million. The dominant clinical features include cutaneous purpura, arthritis and gastrointestinal symptoms. Sometimes nephritis can add, typically as glomerulonephritis with IgA mesangial deposits. Pulmonary, cardiac, genital and neurological symptoms have also been observed. Although the cause is unknown, it is clear that IgA plays a pivotal role in the immunopathogenesis of IgA vasculitis. Only symptomatic treatment is advised in case of self-limited disease. Treatment of severe IgA vasculitis, nephritis or gastrointestinal manifestations, is not established but some studies, which need to be confirmed, reported the benefit of corticosteroids combined with immunosuppressive drugs. Short-term outcome depends of the severity of the gastro-intestinal manifestations. The long-term prognosis is heavily dependent on the presence and severity of nephritis. Studies with prolonged follow-up show up to one third of adult patients reaching end stage renal failure, as for IgA nephropathy. Some authors even suggest that IgA nephropathy and IgA vasculitis would be the same disease.

IgA and FcαRI: Pathological Roles and Therapeutic Opportunities

Immunoglobulin A (IgA) is the most abundant antibody class present at mucosal surfaces. The production of IgA exceeds the production of all other antibodies combined, supporting its prominent role in host-pathogen defense. IgA closely interacts with the intestinal microbiota to enhance its diversity, and IgA has a passive protective role via immune exclusion. Additionally, inhibitory ITAMi signaling via the IgA Fc receptor (FcαRI; CD89) by monomeric IgA may play a role in maintaining homeostatic conditions. By contrast, IgA immune complexes (e.g., opsonized pathogens) potently activate immune cells via cross-linking FcαRI, thereby inducing pro-inflammatory responses resulting in elimination of pathogens. The importance of IgA in removal of pathogens is emphasized by the fact that several pathogens developed mechanisms to break down IgA or evade FcαRI-mediated activation of immune cells. Augmented or aberrant presence of IgA immune complexes can result in excessive neutrophil activation, potentially leading to severe tissue damage in multiple inflammatory, or autoimmune diseases. Influencing IgA or FcαRI-mediated functions therefore provides several therapeutic possibilities. On the one hand (passive) IgA vaccination strategies can be developed for protection against infections. Furthermore, IgA monoclonal antibodies that are directed against tumor antigens may be effective as cancer treatment. On the other hand, induction of ITAMi signaling via FcαRI may reduce allergy or inflammation, whereas blocking FcαRI with monoclonal antibodies, or peptides may resolve IgA-induced tissue damage. In this review both (patho)physiological roles as well as therapeutic possibilities of the IgA-FcαRI axis are addressed.

Galactose-deficient IgA1 in skin and serum from patients with skin-limited and systemic IgA vasculitis

BACKGROUND

IgA vasculitis (IgAV) encompasses a systemic form involving kidneys, gut, skin, or joints, and a skin-limited form. One characteristic feature of systemic IgAV is deposition of galactose-deficient IgA1 (GD-IgA1) in kidneys (as in IgA nephropathy). The relevance of GD-IgA1 for cutaneous vasculitis is unknown.

OBJECTIVE

We investigated whether GD-IgA1 is deposited perivascularly in systemic and also skin-limited IgAV and whether its serum levels differ between both forms.

METHODS

In a case-control study, deposition of GD-IgA1 was analyzed immunohistochemically by KM55 antibody in skin biopsy specimens from 12 patients with skin-limited IgAV and 4 with systemic IgAV. GD-IgA1 levels were compared by enzyme-linked immunosorbent assay in sera from 15 patients each with skin-limited and systemic IgAV and from 11 healthy individuals.

RESULTS

All biopsy samples from systemic IgAV, and also from skin-limited IgAV, revealed perivascular GD-IgA1 deposition. The average GD-IgA1 concentration in serum was significantly higher in systemic IgAV than in skin-limited IgAV, despite overlap between the groups.

LIMITATIONS

Although high GD-IgA1 levels may be predictive of systemic IgAV, patient numbers were too low to determine cutoff values for systemic versus skin-limited IgAV.

CONCLUSION

Perivascular GD-IgA1 deposition is a prerequisite for systemic and skin-limited IgAV; however, high GD-IgA1 levels in some patients with systemic IgAV suggest a dose-dependent effect of GD-IgA1 in IgAV.

The Emerging Role of Pathogenesis of IgA Nephropathy

IgA nephropathy is an autoimmune disease induced by fthe ormation of galactose-deficient IgA1 and anti-glycans autoantibody. A multi-hit hypothesis was promoted to explain full expression of IgA nephropathy. The deposition of immune complex resulted in activation of the complement, increasing oxidative stress, promoting inflammatory cascade, and inducing cell apoptosis via mesangio-podocytic-tubular crosstalk. The interlinked signaling pathways of immune-complex-mediated inflammation can offer a novel target for therapeutic approaches. Treatments of IgA nephropathy are also summarized in our review article. In this article, we provide an overview of the recent basic and clinical studies in cell molecular regulation of IgAN for further treatment interventions.

Serum GDIgA1 levels in children with IgA nephropathy and Henoch-Schönlein nephritis

Introduction

GDIgA1 (galactose deficient IgA1) plays a significant role in the pathogenesis of IgA nephropathy (IgAN) and Henoch-Schönlein nephritis (HSN).

Aim of the study

The aim of this study was to assess the relevance of serum GDIgA1 level as a prognostic marker in children with IgAN and HSN.

Material and methods

41 children were included to the study group (15 IgAN, 26 HSN) and 22 to the control group. The following parameters were evaluated at baseline and endpoint: proteinuria, erythrocyturia, serum creatinine, serum IgA, GFR. A kidney biopsy was performed in all patients and evaluated according to the Oxford Classification (1 – present, 0 – absent: M – mesangial hypercellularity; E– endocapillary hypercellularity; S – segmental sclerosis/adhesion; T – tubular atrophy/interstitial fibrosis), and was calculated as the total score (sum of M, E, S, T). At the end of follow-up, the serum GDIgA1 concentration was measured.

Results

The serum GDIgA1 concentration in patients with IgAN and HSN was significantly higher than in the control group. No significant differences in mean proteinuria, erythrocyturia, GFR, MEST score, or GDIgA1 in serum, as well as the duration of follow-up between IgAN and HSN were observed. Baseline serum IgA concentration and time to kidney biopsy were significantly higher in children with IgAN than in children with HSN. We observed a positive correlation between GDIgA1 and IgA levels (r = 0.53), and GDIgA1 and serum creatinine levels (r = 0.5), as well as negative correlation between GDIgA1 and GFR (r = –0.37).

Conclusions

Serum GDIgA1 level may have a prognostic value in children with IgAN and HSN; however, to fully elucidate its clinical potential further studies performed in larger patient cohorts are required.

Presentation of pediatric Henoch-Schönlein purpura nephritis changes with age and renal histology depends on biopsy timing

BACKGROUND

This study correlates the clinical presentation of Henoch-Schönlein purpura nephritis (HSPN) with findings on initial renal biopsy.

METHODS

Data from 202 pediatric patients enrolled in the HSPN registry of the German Society of Pediatric Nephrology reported by 26 centers between 2008 and 2014 were analyzed. All biopsy reports were re-evaluated for the presence of cellular crescents or chronic pathological lesions (fibrous crescents, glomerular sclerosis, tubular atrophy >5%, and interstitial fibrosis >5%).

RESULTS

Patients with HSPN with cellular glomerular crescents were biopsied earlier after onset of nephritis (median 24 vs 36 days, p = 0.04) than those without, whereas patients with chronic lesions were biopsied later (57 vs 19 days, p < 0.001) and were older (10.3 vs 8.6 years, p = 0.01) than those without. Patients biopsied more than 30 days after the onset of HSPN had significantly more chronic lesions (52 vs 22%, p < 0.001), lower eGFR (88 vs 102 ml/min/1.73m², p = 0.01), but lower proteinuria (2.3 vs 4.5 g/g, p < 0.0001) than patients biopsied earlier. Children above 10 years of age had lower proteinuria (1.98 vs 4.58 g/g, p < 0.001), lower eGFR (86 vs 101 ml/min/1.73m², p = 0.002) and were biopsied significantly later after onset of nephritis (44 vs 22 days, p < 0.001) showing more chronic lesions (45 vs 30%, p = 0.03). Proteinuria and renal function at presentation decreased with age.

CONCLUSIONS

In summary, we find an age-dependent presentation of HSPN with a more insidious onset of non-nephrotic proteinuria, impaired renal function, longer delay to biopsy, and more chronic histopathological lesions in children above the age of 10 years. Thus, HSPN presents more like Immunoglobulin A (IgA) nephritis in older than in younger children.

Serum IgA/C3 and glomerular C3 staining predict severity of IgA nephropathy

BACKGROUND

The aim of this study was to determine whether serum immunoglobulin A/complement factor 3 (IgA/C3) ratio and glomerular C3 staining predict outcome in IgA nephropathy.

METHODS

We collected data for 44 IgA nephropathy children treated with multi-drug combination therapy. The children were retrospectively divided into four groups based on serum IgA/C3 ratio and glomerular C3 staining: group A, IgA/C3 ratio >2.68 (median) and glomerular C3 staining ≥2.0, n = 9; group B, IgA/C3 ratio >2.68 and glomerular C3 staining <2.0, n = 7; group C, IgA/C3 ratio <2.68 and glomerular C3 staining ≥2.0, n = 7; and group D, IgA/C3 ratio <2.68 and glomerular C3 staining <2.0, n = 21. Clinical features; pathology at the first and second renal biopsy and at the latest follow up; and prognosis were analyzed for the four groups.

RESULTS

At the most recent follow up, urinary protein excretion, incidence of hematuria, and serum creatinine in group A were all higher than in group D. At the second biopsy, crescent absence/presence ratio; mesangial hypercellularity, segmental glomerulosclerosis or adhesion, endocapillary hypercellularity, and tubular atrophy/interstitial fibrosis as well as crescents and global glomerulosclerosis (MESTCG) score; and clonicity index in group A were higher than in group D. All patients in group D had normal urine, and the prevalence of persistent nephropathy in group A was higher than in group D.

CONCLUSIONS

Serum IgA/C3 ratio and glomerular C3 staining can predict outcome in IgA nephropathy.

Biomarkers of IgA vasculitis nephritis in children

Henoch–Schönlein purpura is a systemic vasculitis characterized by IgA deposits, which target the skin, joints, and kidneys, among other organs. In children, prognosis is often good but little is known about biomarkers of pediatric nephritis. We hypothesized that biological markers, including cytokines, immunoglobulins, IgA-immune complexes, IgA glycosylation and neutrophil gelatinase-associated lipocalin (NGAL), may discriminate IgA vasculitis (IgAV) pediatric patients with renal involvement from those without renal involvement. Fifty children at the time of IgAV rash between 2010 and 2015 were prospectively enrolled and compared to 21 controls. All patients were assessed for clinical and biological parameters at the time of diagnosis, including the levels of cytokines, immunoglobulins, immune complexes, IgA glycosylation and NGAL in serum and urine. Among IgAV patients, 33 patients exhibited nephritis (IgAV-N) and 17 children were without nephritis (IgAV-woN). The serum level of galactose-deficient (Gd)-IgA1 (p<0.01) and the urinary concentrations of IgA, IgG, IgM, IL-6, IL-8, IL-10, IgA-IgG complexes and IgA-sCD89 complexes (p<0.001 for all) were higher in the IgAV-N patients than in the IgAV-woN patients. Among those markers, urinary IgA and IgM had the highest AUC (0.86 and 0.87 respectively, p<0.0001). This prospective cohort study furthers our understanding of the pathophysiology of IgAV. We identified biomarkers that are able to distinguish patients initially with or without nephritis. To conclude, serum Gd-IgA1 and urinary IgA, IgG, IgM, IL-6, IL-8, IL-10, and IgA-IgG and IgA-sCD89 complexes could identify IgAV pediatric patients with renal involvement at the time of diagnosis.

Serial Galactose-Deficient IgA1 Levels in Children with IgA Nephropathy and Healthy Controls

Galactose-deficient IgA1 (Gd-IgA1) is a key pathogenic factor for IgA nephropathy (IgAN) and a potential biomarker for the disease. This study examined serial serum Gd-IgA1 levels over 1 year in 13 children with IgAN and 40 healthy children, to determine whether or not serum Gd-IgA1 levels changed over time. Subjects were younger than 18 years of age. Follow-up measurements were scheduled 6 and/or 12 months later. Analysis of variance and regression models for repeated measures were used to estimate group and time effects. Serum Gd-IgA1 level was higher in initial samples for IgAN patients compared to those of healthy children (P < 0.0001). Serum Gd-IgA1 levels did not change over time for healthy controls but increased for IgAN patients (P = 0.001). Serum Gd-IgA1 level was elevated for 9 children with IgAN at study entry and remained elevated. Two of the 4 IgAN patients with initially normal Gd-IgA1 levels had a subsequent elevated level. The persistent elevation of the serum Gd-IgA1 level in children with IgAN enhances its utility as a potential diagnostic test for IgAN.

New insights in the pathogenesis of immunoglobulin A vasculitis (Henoch-Schönlein purpura)

Immunoglobulin A vasculitis (IgAV), also referred to as Henoch-Schönlein purpura, is the most common form of childhood vasculitis. The pathogenesis of IgAV is still largely unknown. The disease is characterized by IgA1-immune deposits, complement factors and neutrophil infiltration, which is accompanied with vascular inflammation. Incidence of IgAV is twice as high during fall and winter, suggesting an environmental trigger associated to climate. Symptoms can resolve without intervention, but some patients develop glomerulonephritis with features similar to IgA nephropathy that include hematuria, proteinuria and IgA deposition in the glomerulus. Ultimately, this can lead to end-stage renal disease. In IgA nephropathy immune complexes containing galactose-deficient (Gd-)IgA1 are found and thought to play a role in pathogenesis. Although Gd-IgA1 complexes are also present in patients with IgAV with nephritis, their role in IgAV is disputed. Alternatively, it has been proposed that in IgAV IgA1 antibodies are generated against endothelial cells. We anticipate that such IgA complexes can activate neutrophils via the IgA Fc receptor FcαRI (CD89), thereby inducing neutrophil migration and activation, which ultimately causes tissue damage in IgAV. In this Review, we discuss the putative role of IgA, IgA receptors, neutrophils and other factors such as infections, genetics and the complement system in the pathogenesis of IgA vasculitis.

Immunoglobulin Glycosylation Effects in Allergy and Immunity

PURPOSE OF REVIEW

The aim of this review will be to familiarize the reader with the general area of antibody (Ab) glycosylation and to summarize the known functional roles of glycosylation and how glycan structure can contribute to various disease states with emphasis on allergic disease.

RECENT FINDINGS

Both immunoglobulin (Ig) isotype and conserved Fc glycosylation sites often dictate the downstream activity of an Ab where complexity and degree of glycosylation contribute to its ability to bind Fc receptors (FcRs) and activate complement. Most information on the effects of glycosylation center on IgG in cancer therapy and autoimmunity. In cancer therapy, glycosylation modifications that enhance affinity for activating FcRs are utilized to facilitate immune-mediated tumor cell killing. In autoimmunity, disease severity has been linked to alterations in the presence, location, and composition of Fc glycans. Significantly less is understood about the role of glycosylation in the setting of allergy and asthma. However, recent data demonstrate that glycosylation of IgE at the asparagine-394 site of Cε3 is necessary for IgE interaction with the high affinity IgE receptor but, surprisingly, glycosylation has no effect on IgE interaction with its low-affinity lectin receptor, CD23. Variations in the specific glycoform may modulate the interaction of an Ig with its receptors. Significantly more is known about the functional effects of glycosylation of IgG than for other Ig isotypes. Thus, the role of glycosylation is much better understood in the areas of autoimmunity and cancer therapy, where IgG is the dominant isotype, than in the field of allergy, where IgE predominates. Further work is needed to fully understand the role of glycan variation in IgE and other Ig isotypes with regard to the inhibition or mediation of allergic disease.

Henoch-Schönlein Purpura Nephritis in Children: Prognosis and Treatment Experiences

Henoch-Schönlein purpura is a type of systemic small vessel vasculitis. The dominant manifestation is the cutaneous component, the illness is self-limiting in nature, and the prognosis and outcome depend mostly on renal manifestations. We analysed the associations among clinical and laboratory parameters with the prognosis and outcome of HSP in children hospitalised at the Paediatrics clinic, Clinical Centre, Kragujevac between January 2011 and January 2012. Children who developed nephritis were older on average and all manifested with arthritis, abdominal complaints, microhaematuria, elevated D-dimer levels in the serum, and significant proteinuria and microalbuminuria (≥ 300 mg/L), and two children had pre-existing allergic conditions. All three children with repeatedly positive proteins in the morning sample urine test had significant proteinuria (≥0,5 g/24 h) and microalbuminuria (≥ 300 mg/L). These children had more bursts of rash and more severe and lasting abdominal pain and arthritis compared to children with normal urine tests. They were therefore treated with glucocorticoids and an angiotensin-converting enzyme inhibitor. The glomerular filtration rate measured by determining creatinine clearance was normal in all patients. These patients were diagnosed with Henoch-Schönlein purpura nephritis, and their condition was regularly monitored. Analysis of this group of patients demonstrated that the average age of 8 years and abdominal complaints were indicative of nephritis development.. Because both of these parameters are easily noted at disease onset, we suggest careful monitoring of disease course in these children.

Aberrant IgA1 Glycosylation in IgA Nephropathy: A Systematic Review

OBJECTIVE

Galactose-deficient IgA1 was evaluated in patients with IgA nephropathy(IgAN) and controls in order to determine the predictive value of galactose-deficient IgA1 in cases of IgA nephropathy.

METHODS

PubMed, EMBASE, Cochrane central register of controlled trials, CNKI, CBM disc, and VIP database were searched to identify eligible studies that evaluated a difference in aberrant IgA1 glycosylation in IgAN patients compared with controls. A meta-analysis was conducted to evaluate the impact of galactose-deficient IgA1(Gd-IgA1) levels in different groups.

RESULTS

A total of 22 studies (n = 1657) met inclusion criteria. The mean Newcastle-Ottawa Scale (NOS) score was 7.2 and ranged from 6 to 8. The standard mean difference(SMD) in the meta-analysis of 20 studies of the level of Gd-IgA1 in the serum and/or supernatant of cultured cells was higher in the IgAN group compared with healthy controls as well as in those with other renal diseases (SMD = 1.76, 95% CI = 1.18-2.34, P<0.00001; SMD = 1.05, 95% CI = 0.05-2.04, P = 0.04). The data synthesis suggested that IgAN patients had similar levels of serum Gd-IgA1, with no significant differences, compared with first-degree relatives and Henoch-Schonlein purpura nephritis (HSPN) patients (MD = 0.04, 95% CI = 0.00-0.08, P = 0.05; MD = -46.03, 95% CI = -217.70-125.64, P = 0.60). In addition, the combined MD of 5 studies indicated that there were no significant differences in Gd-IgA1 levels among patients with varying severities of IgAN (MD = 0.02, 95% CI = -0.02-0.05, P = 0.28).

CONCLUSIONS

The pooled evidence suggests that the level of Gd-IgA1 in the serum or supernatant of cultured cells from peripheral blood or tonsils may be a useful biomarker for predicting IgA nephropathy, though the level of Gd-IgA1 was not significantly associated with disease severity.

Circulating midkine in children with Henoch-Schönlein purpura: Clinical implications

BACKGROUND

Midkine (MK) is a heparin-binding growth factor, which behaves like a cytokine, involved in various cellular processes such as cellular proliferation, differentiation, survival, adhesion, and migration. Studies provided evidence for a role of MK in acute and chronic inflammatory processes. The association between midkine and Henoch-Schönlein purpura (HSP) has not yet been explored. The aim of our study was to investigate the potential role of midkine in children with HSP.

METHODS

A total of 152 cases consisting of 92 children with HSP and 60 age- and sex-matched healthy control children were enrolled in this prospective study. Circulating midkine, IL-2, IL-4, IL-6, IL-10, TNF, IFN-γ, and IL-17A was measured in all of the 92 patients and 60 healthy controls. Midkine diagnostic value was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

Renal involvement occurred in 36 of the 92 patients. Circulating midkine level was elevated in children with HSPN than those of patients without renal involvement and of the controls (326.58 (266.58-459.25) pg/ml versus 280.72 (233.67-384.36) pg/ml and 217.3 (198.98-243.65) pg/ml, respectively; P<0.05). Midkine positively correlated with IL-4, IL-6, IL17A, IgA and IgE. The threshold MK concentration of HSPN was 295.58pg/ml, with the sensitivity and specificity of 80.6% and 88.3%, respectively. The area under the receiver operating characteristic (ROC) curve (AUCROC) of MK was 0.902.

CONCLUSIONS

MK seems to be involved in the development of HSP. Measurement of serum levels of MK is helpful in confirming the diagnosis of HSP and predicting HSPN.

Evolution of IgA nephropathy into anaphylactoid purpura in six cases--further evidence that IgA nephropathy and Henoch-Schonlein purpura nephritis share common pathogenesis

BACKGROUND

As the morphological and immunohistochemical manifestations of immunoglobulin A (IgA) nephropathy and Henoch-Schonlein purpura nephritis (HSPN) are very similar, they are considered to share a common pathogenesis. Although HSPN usually develops after the appearance of anaphylactoid purpura, we have encountered patients whose renal symptoms preceded purpura.

METHODS

We reviewed the clinical courses of patients who were first diagnosed with IgA nephropathy, but developed purpura later, at the National Center for Child Health and Development in Tokyo, Japan.

RESULTS

Of the 53 patients who were diagnosed with primary IgA nephropathy at our institute during the study period (March 2002 to July 2015), six (11 %) developed anaphylactoid purpura after the diagnosis of primary IgA nephropathy and therefore met the inclusion criteria. Duration between the onset of nephritis and subsequent appearance of purpura ranged from 5 months to 14 years. One patient reached end-stage renal failure due to IgA nephropathy and developed purpura after renal transplantation. All renal biopsies performed before the appearance of purpura showed mesangial proliferation with predominant IgA deposits. Urinary findings deteriorated in three patients after the appearance of purpura, including one patient who developed rapidly progressive glomerulonephritis. Renal biopsy findings worsened in two patients. At the last observation, two patients showed mild renal insufficiency.

CONCLUSIONS

Our clinical experience and previous reports support the argument that IgA nephropathy and HSPN are different manifestations of a single disease. Hence, it is acceptable to consider that they are variants of a single disease.

The Origin and Activities of IgA1-Containing Immune Complexes in IgA Nephropathy

IgA nephropathy (IgAN) is the most common primary glomerulonephritis, frequently leading to end-stage renal disease, as there is no disease-specific therapy. IgAN is diagnosed from pathological assessment of a renal biopsy specimen based on predominant or codominant IgA-containing immunodeposits, usually with complement C3 co-deposits and with variable presence of IgG and/or IgM. The IgA in these renal deposits is galactose-deficient IgA1, with less than a full complement of galactose residues on the O-glycans in the hinge region of the heavy chains. Research from the past decade led to the definition of IgAN as an autoimmune disease with a multi-hit pathogenetic process with contributing genetic and environmental components. In this process, circulating galactose-deficient IgA1 (autoantigen) is bound by antiglycan IgG or IgA (autoantibodies) to form immune complexes. Some of these circulating complexes deposit in glomeruli, and thereby activate mesangial cells and induce renal injury through cellular proliferation and overproduction of extracellular matrix components and cytokines/chemokines. Glycosylation pathways associated with production of the autoantigen and the unique characteristics of the corresponding autoantibodies in patients with IgAN have been uncovered. Complement likely plays a significant role in the formation and the nephritogenic activities of these complexes. Complement activation is mediated through the alternative and lectin pathways and probably occurs systemically on IgA1-containing circulating immune complexes as well as locally in glomeruli. Incidence of IgAN varies greatly by geographical location; the disease is rare in central Africa but accounts for up to 40% of native-kidney biopsies in eastern Asia. Some of this variation may be explained by genetically determined influences on the pathogenesis of the disease. Genome-wide association studies to date have identified several loci associated with IgAN. Some of these loci are associated with the increased prevalence of IgAN, whereas others, such as deletion of complement factor H-related genes 1 and 3, are protective against the disease. Understanding the molecular mechanisms and genetic and biochemical factors involved in formation and activities of pathogenic IgA1-containing immune complexes will enable the development of future disease-specific therapies as well as identification of non-invasive disease-specific biomarkers.

Long-Term Therapeutic Plasma Exchange to Prevent End-Stage Kidney Disease in Adult Severe Resistant Henoch-Schonlein Purpura Nephritis

A 27-year-old man presented with a palpable purpuric skin rash and joint and abdominal pain in April 2010. He had acute kidney injury and his creatinine quickly deteriorated to 687 μmol/L, with associated nephrotic range proteinuria. Kidney biopsy showed crescentic Henoch-Schonlein nephritis. He was treated with intravenous cyclophosphamide and prednisolone despite which his renal function deteriorated; he required haemodialysis for a short duration and seven sessions of therapeutic plasma exchange (TPE). Renal function improved, but after discharge from hospital he suffered 2 further relapses, each with AKI, in 4 months. Cyclophosphamide was not effective and therefore Rituximab was introduced. He initially had a partial response but his renal function deteriorated despite continued therapy. TPE was the only treatment that prevented rapid renal functional deterioration. A novel long-term treatment strategy involving regular TPE every one to two weeks was initiated. This helped to slow his progression to end-stage kidney disease over a 3-year period and to prolong the need for renal replacement therapy over this time.

IgA Cutaneous Purpura Post-Renal Transplantation in a Patient With Long-Standing IgA Nephropathy: Case Report and Literature Review

BACKGROUND

IgA vasculitis is a small-vessel vasculitis caused by deposition of IgA antibodies in tissues. IgA nephropathy and IgAV have long been considered related conditions.

OBJECTIVE

To assess the prevalence and implications of new-onset Henoch-Schönlein purpura (HSP) after renal transplant in patients with underlying IgA nephropathy.

METHODS

The PubMed database was searched for keywords such as IgAV, IgA vasculitis, Henoch-Schönlein purpura, HSP, IgA nephropathy, and renal transplant.

RESULTS

Two cases of new-onset IgA vasculitis post-renal transplant after stopping the prednisone or receiving seasonal influenza vaccine have been reported. We report the case of new-onset IgA cutaneous vasculitis in a renal transplant patient with IgA nephropathy after reduction in his prednisone dosage.

CONCLUSION

The new development of cutaneous IgA vasculitis is unusual in renal transplant patients with IgA nephropathy. Despite these patients' being immunosuppressed, the presence of IgA vasculitis could signal the recurrence of IgA nephropathy.

Henoch-Schönlein purpura nephritis in children: incidence, pathogenesis and management

BACKGROUND

Henoch-Schönlein purpura (HSP) is one of the most common vasculitides in children. It is manifested by skin purpura, arthritis, abdominal pain, renal involvement, etc. Typically, HSP is considered to be self-limiting, although renal involvement (HSP purpura nephritis, HSPN) is the principal cause of morbidity from this disease. For this reason, it is important to clarify the mechanism of onset and clinical manifestations of HSPN and to ascertain the most appropriate treatment for HSPN. In this article, we review the updated pathophysiology and treatment strategies for HSPN.

DATA SOURCES

We searched databases including PubMed, Elsevier and Wanfang for the following key words: Henoch-Schönlein purpura, nephritis, mechanism and treatment, and we selected those publications written in English that we judged to be relevant to the topic of this review.

RESULTS

Based on the data present in the literature, we reviewed the following topics: 1) the possible pathogenesis of HSPN: several studies suggest that immunoglobulin A immune complexes deposit in the mesangium and induce renal injury; 2) multiple-drug treatment for HSPN: although there have been few evidence-based treatment strategies for HSPN, several studies have suggested that immunosuppressive drugs and multiple drug combination therapy were effective in ameliorating proteinuria and histological severity.

CONCLUSIONS

HSPN is a severe disease of childhood. To better understand this disease, detailed investigations into the pathogenesis of HSPN and prospective randomized controlled treatment studies on children with severe HSPN are needed.

Toll-like receptors, immunoproteasome and regulatory T cells in children with Henoch-Schönlein purpura and primary IgA nephropathy

BACKGROUND

Henoch-Schönlein purpura (HSP) nephritis and primary IgA nephropathy (pIgAN) present with glomerular IgA deposits, but differ with regard to clinical features. The suspected involvement of different immune system pathways is largely unknown.

METHODS

This study was aimed at investigating some of the immunological features including Toll-like receptors (TLR), proteasome (PS)/immunoproteasome (iPS) switch, and the regulatory T cell system (Treg/Th17 cells) in 63 children with HSP with/without renal involvement and in 25 with pIgAN. Real-time PRC (Taqman) was used to quantify mRNA levels in peripheral blood mononuclear cells (PBMC).

RESULTS

The expression of mRNAs encoding for TLR4 in both HSP and pIgAN was higher than in controls (HC) and in both diseases FoxP3mRNA and TGF-β1mRNA expression was significantly lower than in HC. A switch from PS to iPS (LMP2/β1) was detected only in PBMC of HSP and it correlated with the level of TLR2mRNA, which was selectively increased only in children with HSP.

CONCLUSION

Children with HSP and pIgAN present with similar signs of engagement of the innate immunity and regulatory T cell depression. The increased immunoproteasome switch, which correlated with TLR2 activation, may suggest an innate immunity pathway peculiar to HSP vasculitic presentation. This research area also deserves further investigation for possible therapeutic applications.

Henoch-Schönlein purpura nephritis in children

Henoch-Schönlein purpura (HSP) is the most common vasculitis in children, in whom prognosis is mostly dependent upon the severity of renal involvement. Nephritis is observed in about 30% of children with HSP. Renal damage eventually leads to chronic kidney disease in up to 20% of children with HSP nephritis in tertiary care centres, but in less than 5% of unselected patients with HSP, by 20 years after diagnosis. HSP nephritis and IgA nephropathy are related diseases resulting from glomerular deposition of aberrantly glycosylated IgA1. Although both nephritides present with similar histological findings and IgA abnormalities, they display pathophysiological differences with important therapeutic implications. HSP nephritis is mainly characterized by acute episodes of glomerular inflammation with endocapillary and mesangial proliferation, fibrin deposits and epithelial crescents that can heal spontaneously or lead to chronic lesions. By contrast, IgA nephropathy normally presents with slowly progressive mesangial lesions resulting from continuous low-grade deposition of macromolecular IgA1. This Review highlights the variable evolution of similar clinical and histological presentations among paediatric patients with HSP nephritis, which constitutes a challenge for their management, and discusses the treatment of these patients in light of current guidelines based on clinical evidence from adults with IgA nephropathy.

Identification of distinct glycoforms of IgA1 in plasma from patients with immunoglobulin A (IgA) nephropathy and healthy individuals

Immunoglobulin A nephropathy (IgAN) is the most common form of glomerulonephritis worldwide and is histologically characterized by the deposition of IgA1 and consequent inflammation in the glomerular mesangium. Prior studies suggested that serum IgA1 from IgAN patients contains aberrant, undergalactosylated O-glycans, for example, Tn antigen and its sialylated version, SialylTn (STn), but the mechanisms underlying aberrant O-glycosylation are not well understood. Here we have used serial lectin separation technologies, Western blot, enzymatic modifications, and mass spectrometry to explore whether there are different glycoforms of IgA1 in plasma from patients with IgAN and healthy individuals. Although total plasma IgA in IgAN patients was elevated ∼ 1.6-fold compared with that in healthy donors, IgA1 in all samples was unexpectedly separable into two distinct glycoforms: one with core 1 based O-glycans, and the other exclusively containing Tn/STn structures. Importantly, Tn antigen present on IgA1 from IgAN patients and controls was convertible into the core 1 structure in vitro by recombinant T-synthase. Our results demonstrate that undergalactosylation of O-glycans in IgA1 is not restricted to IgAN and suggest that in vivo inefficiency of T-synthase toward IgA1 in a subpopulation of B or plasma cells, as well as overall elevation of IgA, may contribute to IgAN pathogenesis.

Advances in our understanding of the pathogenesis of Henoch-Schönlein purpura and the implications for improving its diagnosis

Henoch-Schönlein purpura (HSP) is a leukocytoclastic vasculitis classically characterized by palpable purpura, arthritis, abdominal pain and renal disease. In this article, we summarize our current understanding of the pathogenesis of HSP and the implications for improving its diagnosis. Although the pathogenesis of HSP is not fully understood yet, exciting new information has emerged in recent years, leading to a better understanding of its pathogenesis. Here, we discuss genetic predisposition, immunoglobulins with a particular emphasis on IgA1, activated complements, cytokines and chemokines, abnormal coagulation and autoantibodies in the underlying pathogenic mechanisms. Finally, diagnostic criteria for HSP developed by institutions such as the American College of Rheumatology and the European League against Rheumatism/Paediatric Rheumatology European Society were proposed to improve early detection and diagnosis.