IgA nephropathy and IgA vasculitis with nephritis have a shared feature involving galactose-deficient IgA1-oriented pathogenesis

Intestinal epithelium dysfunctions cause IgA deposition in the kidney glomeruli of intestine-specific Ap1m2-deficient mice

BACKGROUND

Intestinal epithelial cells (IECs) serve as robust barriers against potentially hostile luminal antigens and commensal microbiota. Epithelial barrier dysfunction enhances intestinal permeability, leading to leaky gut syndrome (LGS) associated with autoimmune and chronic inflammatory disorders. However, a causal relationship between LGS and systemic disorders remains unclear. Ap1m2 encodes clathrin adaptor protein complex 1 subunit mu 2, which facilitates polarized protein trafficking toward the basolateral membrane and contributes to the establishment of epithelial barrier functions.

METHODS

We generated IEC-specific Ap1m2-deficient (Ap1m2ΔIEC) mice with low intestinal barrier integrity as an LSG model and examined the systemic impact.

FINDINGS

Ap1m2ΔIEC mice spontaneously developed IgA nephropathy (IgAN)-like features characterized by the deposition of IgA-IgG immune complexes and complement factors in the kidney glomeruli. Ap1m2 deficiency markedly enhanced aberrantly glycosylated IgA in the serum owing to downregulation and mis-sorting of polymeric immunoglobulin receptors in IECs. Furthermore, Ap1m2 deficiency caused intestinal dysbiosis by attenuating IL-22-STAT3 signaling. Intestinal dysbiosis contributed to the pathogenesis of IgAN because antibiotic treatment reduced aberrantly glycosylated IgA production and renal IgA deposition in Ap1m2ΔIEC mice.

INTERPRETATION

IEC barrier dysfunction and subsequent dysbiosis by AP-1B deficiency provoke IgA deposition in the mouse kidney. Our findings provide experimental evidence of a pathological link between LGS and IgAN.

FUNDING

AMED, AMED-CREST, JSPS Grants-in-Aid for Scientific Research, JST CREST, Fuji Foundation for Protein Research, and Keio University Program for the Advancement of Next Generation Research Projects.

Pediatric IgA-Dominant Infection-Related Glomerulonephritis

The concept of infection-related glomerulonephritis (IRGN) has been introduced as adults diagnosed with glomerulonephritis often have coexisting active infections. Furthermore, IgA-dominant IRGN is associated with staphylococcal infections in adults with comorbidities, which often progress to end-stage renal disease. Little is known about IgA-dominant IRGN in children, and no consensus for a management strategy of this condition has been reached. We describe the case of a 9-year-old boy with IgA-dominant IRGN that was diagnosed using specific staining for nephritis-associated plasmin receptor (NAPlr)/plasmin activity and galactose-deficient IgA1 (Gd-IgA1), a marker of IgA nephropathy. The patient was successfully treated using a combination of prednisolone, mizoribine (an immunosuppressive drug), and lisinopril (an angiotensin-converting enzyme inhibitor) and three courses of methylprednisolone pulse therapy. The patient was admitted to our hospital with generalized edema, gross hematuria, proteinuria, hypertension, and renal dysfunction. Hypocomplementemia contributed to a diagnosis of IRGN, although the causative organism was unknown. A renal biopsy performed when the patient presented with nephrotic syndrome showed IgA deposition, positive staining for NAPlr, and negative staining for Gd-IgA1, in addition to findings consistent with IRGN, leading to a pathologic diagnosis of IgA-dominant IRGN. The histological staining for NAPlr/plasmin activity and Gd-IgA1, together with clinical symptoms, could be helpful for diagnosing IgA-dominant IRGN. Our findings indicate that otherwise healthy children can also develop IgA-dominant IRGN. Therefore, early diagnosis and aggressive treatment should be considered when IgA-dominant IRGN is suspected to avoid the possibility of incomplete recovery of renal function.

Liver Disease-Associated Glomerulopathies

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infect a significant number of individuals globally and their extra-hepatic manifestations, including glomerular disease, are well established. Additionally, liver disease-associated IgA nephropathy is the leading cause of secondary IgA nephropathy with disease course varying from asymptomatic urinary abnormalities to progressive kidney injury. Herein we provide an updated review on the epidemiology, pathogenesis, clinical manifestations, and treatment of HBV- and HCV-related glomerulonephritis as well as IgA nephropathy in patients with liver disease. The most common HBV-related glomerulonephritis is membranous nephropathy, although membranoproliferative glomerulonephritis and podocytopathies have been described. The best described HCV-related glomerulonephritis is cryoglobulinemic glomerulonephritis occurring in about 30% of patients with mixed cryoglobulinemic vasculitis. The mainstay of treatment for HBV-GN and HCV-GN is antiviral therapy, with significant improvement in outcomes since the emergence of the direct-acting antivirals. However, cases with severe pathology and/or a more aggressive disease trajectory can be offered a course of immunosuppression, commonly anti-CD20 therapy, particularly in the case of cryoglobulinemic glomerulonephritis.

Examining the association between serum galactose-deficient IgA1 and primary IgA nephropathy: a systematic review and meta-analysis

BACKGROUND

IgA nephropathy (IgAN) is a common primary glomerular disease. The O-glycosylation status of IgA1 plays a crucial role in disease pathophysiology. The level of poorly-O-galactosylated IgA1, or galactose-deficient IgA1 (Gd-IgA1), has also been identified as a potential biomarker in IgAN. We sought to examine the value of serum Gd-IgA1 as a biomarker in IgAN, by investigating its association with clinical, laboratory, and histopathological features of IgAN.

METHODS

The review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations and was registered in PROSPERO (CRD42021287423). The literature search was conducted in PubMed, Web of Science, Cochrane, and Scopus, and the selected articles were evaluated for eligibility based on predefined criteria. The methodological quality of the studies was assessed using the Newcastle-Ottawa Scale. Statistical analysis was performed to calculate effect sizes and assess heterogeneity among the studies.

RESULTS

This review analyzed 29 out of 1,986 studies, conducted between 2005 and 2022, with participants from multiple countries. Gd-IgA1 levels were not associated with age and gender, while associations with hypertension, hematuria, and proteinuria were inconsistent. In the meta-analyses, a correlation between serum Gd-IgA1 and estimated glomerular filtration rate was identified, however, the relationships between Gd-IgA1 levels and chronic kidney disease (CKD) stage and progression to kidney failure were inconsistent.

CONCLUSIONS

Serum Gd-IgA1 levels were not associated with validated prognostic risk factors, but were negatively correlated with kidney function. Further research in larger studies using standardized assays are needed to establish the value of Gd-IgA1 as a prognostic risk factor in IgAN.

IgA nephropathy in a boy with frequently relapsing nephrotic syndrome

A Japanese boy developed nephrotic syndrome (NS) and had microscopic hematuria at 8 years old. Renal biopsy was performed. Light microscopy study revealed mesangial proliferation and all immunofluorescent stains (including IgA) were negative, so he was diagnosed with non-IgA diffuse mesangial proliferation (DMP). Complete remission was achieved at 13 days after the initiation of oral prednisolone, and hematuria also disappeared 3 days later, but the patient developed frequently relapsing nephrotic syndrome. Cyclosporine A (CyA) was introduced at 10 years old, and there were no relapses between then and when it was discontinued at 12 years old. A second renal biopsy revealed minimal change without CyA nephrotoxicity. However, there was repeated relapse of NS after discontinuation, so CyA was reintroduced 8 months later, and NS remained in remission thereafter. Microscopic hematuria appeared at 13 years old, however, with gross hematuria appearing at the time of infection. A third renal biopsy revealed mesangial proliferation with IgA-dominant deposition, so the patient was diagnosed with IgA nephropathy. Currently (14 years old), CyA treatment has been discontinued and the patient is undergoing lisinopril therapy for IgA nephropathy, but there are still relapses of NS. To the best of our knowledge, there have been no previous reports of a patient with non-IgA DMP at the onset of NS who had later development of IgA nephropathy. The patient showed non-IgA DMP at the onset, suggesting that NS with non-IgA DMP and IgA nephropathy has some common pathophysiology. Treatment for NS, such as PSL and/or CyA treatment, may suppress the clinical manifestation of late IgA nephropathy.

Characteristics of renal pathology and coagulation function in IgA nephropathy and IgA vasculitis associated nephritis

BACKGROUND

The objective of this study is to investigate the clinical and pathological differences between patients with IgA nephropathy (IgAN) and IgA vasculitis associated nephritis (IgAVN).

METHODS

A total of 253 patients with IgAN and 71 patients with IgAVN were retrospectively included in the study, and clinical and laboratory data were collected and analysed.

RESULTS

Compared with IgAVN group, months from onset to kidney biopsy were significantly prolonged in IgAN patients because of the lack of obvious symptoms such as rash, abdominal symptoms, and joint pain (13.5 ± 26.6 vs. 10.2 ± 31.6 months, P = 0.007), and the levels of serum creatinine (92.3 ± 94.7 vs. 68.9 ± 69.2 µmol/L, P = 0.015) was higher and eGFR (99.1 ± 35.2 vs. 123.4 ± 41.8 mL/min/1.73m2, P < 0.001) was lower in IgAN group. The pathological results revealed that patients with IgAN have a greater degree of chronic kidney injury compared to patients with IgAVN. In addition, the levels of plasma D-Dimers (1415.92 ± 1774.69 vs. 496.78 ± 711.91 ng/mL, P < 0.001) and fibrinogen degradation products (FDP) (3.92 ± 4.73 vs. 1.63 ± 2.46 µg/mL, P = 0.001) were significantly higher in IgAVN patients than in IgAN patients. The deposition of fibrinogen in the renal tissues was more severe and the cumulative partial remission rate was higher in patients with IgAVN as compared to those with IgAN (P = 0.001).

CONCLUSIONS

In comparison, IgAN patients had poorer renal function, whereas IgAVN patients had more severe coagulation abnormalities. These findings provide a basis for the differentiation of the two diseases at an early stage.

Ethnicity and IgA nephropathy: worldwide differences in epidemiology, timing of diagnosis, clinical manifestations, management and prognosis

Immunoglobulin A nephropathy (IgAN), the most common primary glomerulonephritis, is one of the major causes of end-stage renal disease. Significant variances in epidemiology, clinical manifestation, timing of diagnosis, management and renal prognosis of IgAN have been reported worldwide. The incidence of IgAN is the most frequent in Asia, followed by Europe, and lower in Africa. Moreover, Asian patients show more frequent acute lesions in renal histology and present poorer renal outcomes compared with Caucasians. The comorbidities also show the difference between Asians and Caucasians. Although the frequency of gross hematuria with upper respiratory tract infection is not different, comorbidities with gastrointestinal diseases are reported to be higher in Europe. Recently, genetic studies for variant ethnic patients revealed widely ranging genetic risks in each ethnicity. A genetic risk score is most elevated in Asians, intermediate in Europeans and lowest in Africans, consistent with the disease prevalence of IgAN globally. Ethnic variance might be highly affected by the difference in genetic background. However, it is also essential to mention that the different timing of diagnosis due to variant urinary screening systems and the indication for renal biopsy in different countries may also contribute to these variances. The management of IgAN also varies internationally. Currently, several novel therapies based on the pathogenesis of IgAN are being assessed and are expected to become available soon. Further understanding the ethnic variance of IgAN might help establish individualized care for this disease. Here, we review the issues of ethnic heterogeneities of IgAN.

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.

Pediatric Mesangial Proliferative Glomerulonephritis Has Increased the Platelet Thrombus Formation Potentials under High-Shear Flow Condition

INTRODUCTION

Blood coagulation is associated with glomerulonephritis (GN) pathophysiology. Using whole-blood-based rotational thromboelastometry, we recently reported that the degree of hypercoagulability in pediatric patients with immunoglobulin A nephropathy (IgAN), a GN, might be associated with pathological severity. To further clarify the coagulation status of mesangial proliferative GN (MesPGN), we assessed the platelet thrombus formation (PTF) under high-shear flow using a microchip-based flow chamber system (T-TAS®).

METHODS

Thirty-four pediatric patients definitively diagnosed with MesPGN by renal biopsy at Nara Medical University Hospital between 2015 and 2022 were enrolled, and 29 patients (case group; median age, 8.0 years) were assessed. Microchips coated with collagen (PL-chip) were used to assess PTF at high-shear in whole blood. The times to increase by 10 and 30 kPa (T10 and T30) from baseline were calculated and compared with those of the pediatric controls. Changes in the parameters during the treatment course and the relationship between pathological severity and the parameters were evaluated.

RESULTS

T10 and T30 parameters in the PL-chip were significantly shorter, and the area under the curves were greater in the case group than those in the control group (both p < 0.05). Each parameter was enhanced during the 3-week treatment but improved after the end of treatment. No significant relationship was observed between pathological severity and these parameters. Little PTF difference was observed between IgAN and Henoch-Schönlein purpura nephritis.

CONCLUSIONS

Pediatric MesPGN increased the potential for PTF under high-shear flow conditions.

Comparative study on clinicopathological features and prognosis of IgA vasculitis nephritis and IgA nephropathy in children

BACKGROUND

IgA vasculitis nephritis (IgAVN) and IgA nephropathy (IgAN) share several clinical and pathological characteristics, though distinctions also exist. Their interrelation, however, remains undefined. This study investigates the clinicopathological divergences and prognostic disparities in pediatric patients with IgAVN and IgAN.

METHODS

Our study encompasses 809 pediatric patients with IgAVN and 236 with IgAN, all of whom underwent kidney biopsy. We utilized the Semiquantitative Classification (SQC) scoring system to juxtapose the pathologies of the two conditions, and performed a COX regression analysis to examine factors influencing their prognoses.

RESULTS

Both patient groups demonstrated a predominance of males. A seasonality was observed, with a higher incidence of IgAN in the summer, and IgAVN in the fall (P < 0.0001). Patients with IgAN exhibited more severe tubulointerstitial injury, higher chronicity index, and total biopsy scores compared to those with IgAVN (P < 0.0001). Mesangial deposition intensity of complement C3, and the rate of pure IgA deposition, were found to be greater in patients with IgAVN compared to those with IgAN (P < 0.0001). The intensity of IgA deposition was also significantly higher in IgAVN patients (P = 0.003). IgAVN demonstrated a superior prognosis, with a higher rate of kidney remission (P < 0.0001). COX regression analysis indicated that interstitial fibrosis, as identified in the SQC pathology system, was associated with the prognosis of both conditions. Furthermore, the findings suggest that IgA deposition levels (IgA +  + and IgA +  + +) could potentially influence the prognosis of IgAVN.

CONCLUSIONS

Compared to IgAVN, IgAN manifests more severely with regard to renal impairment, interstitial damage, and prognosis. The disparities in immune complex deposition levels and locations within the kidneys support the hypothesis of IgAVN and IgAN as distinct diseases. Interstitial fibrosis may serve as a key pathological indicator within the SQC system associated with kidney prognosis in children with IgAVN and IgAN. The degree of IgA deposition could also be linked with the prognosis of IgAVN.

Fc receptors act as innate immune receptors during infection?

Innate immunity constitutes the first nonspecific immunological line of defense against infection. In this response, a variety of mechanisms are activated: the complement system, phagocytosis, and the inflammatory response. Then, adaptive immunity is activated. Major opsonization mediators during infections are immunoglobulins (Igs), the function of which is mediated through Fc receptors (FcRs). However, in addition to their role in adaptive immunity, FcRs have been shown to play a role in innate immunity by interacting directly with bacteria in the absence of their natural ligands (Igs). Additionally, it has been hypothesized that during the early phase of bacterial infection, FcRs play a protective role via innate immune functions mediated through direct recognition of bacteria, and as the infection progresses to later phases, FcRs exhibit their established function as receptors in adaptive immunity. This review provides detailed insight into the potential role of FcRs as innate immune mediators of the host defense against bacterial infection independent of opsonins.

Neutrophil extracellular traps involved in the pathogenesis of IgA vasculitis: Confirmed in two IgAV rat models

BACKGROUND

Neutrophil extracellular traps (NETs) have been found to play a role in the development of autoimmune diseases. In the past two years, studies have demonstrated a significantly increase of NETs in skin tissues during the early stages of IgAV, indicating their involvement in disease activity among children with IgAV. However, the presence of NETs in IgAV animal models has not yet been reported. The objective of this study is to investigate whether NETs are involved in the pathogenesis of IgA vasculitis (IgAV) rats.

METHODS

Twenty-four SD rats were randomly divided into three groups: the ovalbumin group, the gliadin group, and the control group. The IgAV rat models were established administering Indian ink with ovalbumin (ovalbumin group) or gliadin (gliadin group) with Freund's complete adjuvant. The cell-free DNA (cf-DNA) was quantified by using dsDNA quantification kit, while the levels of Immunoglobulins, complement C3 and myeloperoxidase-DNA (MPO-DNA) in serum were tested using enzyme linked immunosorbent assay (ELISA). The IgA, complement C3 and NETs in tissues were detected through multiple immunofluorescences.

RESULTS

Both the ovalbumin group and gliadin group showed IgA and C3 deposition in various tissues, including the glomerular mesangial region, skin, and digestive tract, while the control group showed no such deposition. The levels of circulatory cf-DNA and MPO-DNA, which are components of NETs, were significantly elevated in both ovalbumin and gliadin groups compared with the control group. Furthermore, the presence of NETs were found in gastrointestinal and renal tissues of the ovalbumin and gliadin groups, but not in the control group.

CONCLUSIONS

IgAV model rat can be established through the combination of ovalbumin and gliadin with Indian ink and Freund's complete adjuvant. This study provides the first confirmation that NETs are involved in the pathogenesis of IgAV rat.

Comparative proteomic analysis of glomerular proteins in IgA nephropathy and IgA vasculitis with nephritis

BACKGROUND

IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN) are related glomerular diseases characterized by marked similarities in immunological and histological findings. We herein performed a comparative proteomic analysis of glomerular proteins in IgAN and IgAVN.

METHODS

We used renal biopsy specimens from 6 IgAN patients without nephrotic syndrome (NS) (IgAN-I subgroup), 6 IgAN patients with NS (IgAN-II subgroup), 6 IgAVN patients with 0-8.0% of glomeruli with crescent formation (IgAVN-I subgroup), 6 IgAVN patients with 21.2-44.8% of glomeruli with crescent formation (IgAVN-II subgroup), 9 IgAVN patients without NS (IgAVN-III subgroup), 3 IgAVN patients with NS (IgAN-IV subgroup), and 5 control cases. Proteins were extracted from laser microdissected glomeruli and analyzed using mass spectrometry. The relative abundance of proteins was compared between groups. An immunohistochemical validation study was also performed.

RESULTS

More than 850 proteins with high confidence were identified. A principal component analysis revealed a clear separation between IgAN and IgAVN patients and control cases. In further analyses, 546 proteins that were matched with ≥ 2 peptides were selected. The levels of immunoglobulins (IgA, IgG, and IgM), complements (C3, C4A, C5, and C9), complement factor H-related proteins (CFHR) 1 and 5, vitronectin, fibrinogen chains, and transforming growth factor-β inducible gene-h3 were higher (> 2.6 fold) in the IgAN and IgAVN subgroups than in the control group, whereas hornerin levels were lower (< 0.3 fold). Furthermore, C9 and CFHR1 levels were significantly higher in the IgAN group than in the IgAVN group. The abundance of some podocyte-associated proteins and glomerular basement membrane (GBM) proteins was significantly less in the IgAN-II subgroup than in the IgAN-I subgroup as well as in the IgAVN-IV subgroup than in the IgAVN-III subgroup. Among the IgAN and IgAVN subgroups, talin 1 was not detected in the IgAN-II subgroup. This result was supported by immunohistochemical findings.

CONCLUSIONS

The present results suggest shared molecular mechanisms for glomerular injury in IgAN and IgAVN, except for enhanced glomerular complement activation in IgAN. Differences in the protein abundance of podocyte-associated and GBM proteins between IgAN and IgAVN patients with and without NS may be associated with the severity of proteinuria.

Role of abnormal glycosylated IgA1 and interstitial transformation of glomerular endothelial cells in the development and progression of IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is a common primary renal disease in childhood.

METHODS

Twenty blood samples and renal tissue from patients with IgAN, 20 blood samples from healthy children and 10 normal renal tissue were collected. Serum Gd-IgA1 and renal Gd-IgA1, CD31, α-SMA and vimentin were measured.

RESULTS

The serum Gd-IgA1 concentration in the IgAN group was significantly higher. Gd-IgA1 was not expressed in normal kidneys, which was positive in the IgAN group. Gd-IgA1 levels in serum and renal tissue were not related. The expression of CD31 decreased significantly in IgAN group, while the expression of α-SMA and vimentin increased significantly. There was no significant correlation between the renal concentration of Gd-IgA1 and CD31, α-SMA and vimentin.

CONCLUSION

The increased Gd-IgA1 in the serum and kidney may promote the pathogenesis of IgAN. The serum Gd-IgA1 cannot predict the extent of its deposition in the kidney. Endothelial mesenchymal transition (EndMT) may be involved in the pathogenesis of renal fibrosis in IgAN.

Secondary IgA Nephropathy and IgA-Associated Nephropathy: A Systematic Review of Case Reports

Primary (pIgAN), secondary IgA nephropathy (sIgAN), and IgA-associated nephropathy can be distinguished. While pIgAN has been thoroughly studied, information about the etiology of sIgAN remains scarce. As concerns sIgAN, several studies suggest that different etiologic factors play a role and ultimately lead to a pathophysiologic process similar to that of pIgAN. In this article, we review a vast number of cases in order to determine the novel putative underlying diseases of sIgAN. Moreover, updates on the common pathophysiology of primary disorders and sIgAN are presented. We identified liver, gastrointestinal, oncological, dermatological, autoimmune, and respiratory diseases, as well as infectious, iatrogenic, and environmental factors, as triggers of sIgAN. As novel biological therapies for listed underlying diseases emerge, we suggest implementing drug-induced sIgAN as a new significant category. Clinicians should acknowledge the possibility of sIgAN progression in patients treated with TNF-α inhibitors, IL-12/IL-23-inhibitors, immune checkpoint inhibitors, CTLA-4, oral anticoagulants, thioureylene derivatives, and anti-vascular endothelial growth factor drugs.

Aberrant Gut Microbiome Contributes to Barrier Dysfunction, Inflammation, and Local Immune Responses in IgA Nephropathy

INTRODUCTION

Numerous research works have shown that serum Gal-deficient (Gd) IgA1 levels are increased in IgA nephropathy (IgAN) patients and these levels are a dangerous risk factor for IgAN. A relationship between the gut microbiota and IgAN has been reported. Whether the gut microbiota participates in the pathogenesis of IgAN was still controversial.

METHODS

We evaluated changes in the gut flora and the levels of Gd-IgA1 in IgAN patients and healthy controls (HCs). We investigated the Gd-IgA1 levels in both blood and urine specimens. C57BL/6 mice were given a broad-spectrum antibiotic cocktail to deplete the endogenous gut flora. We established a model of IgAN in pseudosterile mice and investigated the expression of the markers of intestinal permeability, inflammation, and local immune responses.

RESULTS

Studies have shown that the levels of certain gut flora differ between IgAN patients and HCs. Moreover, elevated Gd-IgA1 levels were found in both the serum and urine. Interestingly, Coprococcus, Dorea, Bifidobacterium, Blautia, and Lactococcus, selected from 10 candidate biomarkers to predict risk in IgAN patients according to random forest analysis, were inversely associated with urinary Gd-IgA1 levels. Notably, the urine level of Gd-IgA1 could best distinguish IgAN patients from HCs. Additionally, the degree of kidney damage in pseudosterile mice with IgAN was more severe than that in mice with IgAN. Furthermore, the markers of intestinal permeability were significantly elevated in pseudosterile IgAN mice. Moreover, the inflammation responses (TLR4, MyD88, and NF-κB in intestinal and renal tissues; TNF-α and IL-6 in serum) and local immune responses (BAFF and APRIL in intestinal tissue) were upregulated in pseudosterile IgAN mice.

CONCLUSIONS

The urine Gd-IgA1 level may be as a biomarker for the early screening of potential IgAN, and gut microbiota dysbiosis was demonstrated in IgAN, which might involve the dysfunction of the mucosal barrier, inflammation, and local immune responses.

cnm-positive Streptococcus mutans is associated with galactose-deficient IgA in patients with IgA nephropathy

The presence of Streptococcus mutans expressing Cnm protein encoded by cnm (cnm-positive S. mutans) in the oral cavity is associated with immunoglobulin A (IgA) nephropathy (IgAN). However, the precise mechanism by which cnm-positive S. mutans is involved in the pathogenesis of IgAN remains unclear. The present study evaluated glomerular galactose-deficient IgA1 (Gd-IgA1) to clarify the association between the presence of cnm-positive S. mutans and glomerular Gd-IgA1 in patients with IgAN. The presence of S. mutans and cnm-positive S. mutans was evaluated by polymerase chain reaction in saliva specimens from 74 patients with IgAN or IgA vasculitis. Immunofluorescent staining of IgA and Gd-IgA1 using KM55 antibody in clinical glomerular tissues was then performed. There was no significant association between the glomerular staining intensity of IgA and the positive rate of S. mutans. However, there was a significant association between the glomerular staining intensity of IgA and the positive rate of cnm-positive S. mutans (P < 0.05). There was also a significant association between the glomerular staining intensity of Gd-IgA1 (KM55) and the positive rate of cnm-positive S. mutans (P < 0.05). The glomerular staining intensity of Gd-IgA1 (KM55) was not associated with the positive rate of S. mutans. These results suggest that cnm-positive S. mutans in the oral cavity is associated with the pathogenesis of Gd-IgA1 in patients with IgAN.

Tubulointerstitial B-cell infiltration and tertiary lymphoid tissue in adult-onset immunoglobulin A vasculitis with nephritis

PURPOSE

This study aimed to examine tubulointerstitial B-cell infiltration in patients with adult-onset immunoglobulin A vasculitis (IgAV) and nephritis (IgAV-N), and to evaluate whether B-cell infiltration correlated with clinicopathological variables at kidney biopsy and with short-term renal outcomes.

METHODS

Twenty patients with adult-onset IgAV-N and 10 control patients with thin basement membrane nephropathy (TBMN) were retrospectively examined. The lymphatic organization was graded based on B-cell infiltration and was classified into 4 groups: 0-T cells without B cells, 1-scattered B and T cells, 2-clustered B and T cells, and 3-nodular compartmentally arranged B- and T-cell aggregates, equivalent to tertiary lymphoid tissue (TLT).

RESULTS

The B-cell infiltration grade was significantly higher in patients with IgAV-N than in patients with TBMN, and no age differences were observed. The B-cell infiltration grade in patients with IgAV-N was significantly correlated with age, serum IgA level, renal dysfunction, and tubulointerstitial injury parameters, but was not correlated with duration after purpura or glomerular injury parameters. Most patients with IgAV-N were treated with corticosteroids. The proteinuria level was significantly decreased, but renal function was not improved in 12 patients after the 24-month follow-up compared with the values at baseline. The B-cell infiltration grade was significantly correlated with renal dysfunction after 24 months of follow-up.

CONCLUSIONS

The B-cell infiltration grade in patients with IgAV-N was associated with renal dysfunction and tubulointerstitial injuries but not with glomerular injury parameters. B-cell infiltration and TLT might have a pathologically significant role in irreversible renal dysfunction in patients with early phase adult-onset IgAV-N.

The significance of galactose-deficient immunoglobulin A1 staining in kidney diseases with IgA deposition

BACKGROUND

This study investigated the significance of galactose-deficient immunoglobulin A1 staining in kidney diseases with IgA deposition.

METHODS

A total of 120 patients with IgA-dominant deposition in kidney tissues were enrolled and divided into four groups: primary IgA nephropathy (PIgAN), secondary IgA nephropathy (SIgAN), monotypic IgA nephropathy (MIgAN), and IgA variant monoclonal gammopathy of renal significance (IgA-MGRS). KM55 (the antibody of galactose-deficient immunoglobulin A1), IgA subtypes, and complement pathway factors (properdin, C4d, and C1q) were detected through immunofluorescence or immunohistochemistry analysis.

RESULTS

KM55 and IgA double staining showed colocalization within glomeruli in all cases except for IgA-MGRS, which showed negative or weak staining of KM55 but strong staining of IgA. The PIgAN group showed the highest intensity of KM55 and KM55/IgA ratio, while these values in the IgA-MGRS group were the lowest (P < 0.01). A KM55/IgA quantified ratio of 0.78 was the optimal cut-off value to distinguish PIgAN from SIgAN, whereas a cut-off value of 0.21 was optimal to distinguish between MIgAN and IgA-MGRS. The clinicopathological characteristics showed significant differences as the groups were divided by diseases with optimal cut-off values, and these differences corresponded to the pathogenesis of each disease entity.

CONCLUSIONS

PIgAN, SIgAN, and MIgAN are caused by the deposition of abnormally glycosylated IgA1 whereas IgA-MGRS is not. The KM55/IgA quantified ratio is valuable in distinguishing PIgAN from SIgAN, as well as MIgAN from IgA-MGRS.

Serological and histopathological assessment of galactose-deficient immunoglobulin A1 deposition in kidney allografts: A multicenter prospective observational study

BACKGROUND

Recurrent immunoglobulin A (IgA) nephropathy is an important risk factor for kidney allograft loss. However, there is no classification system for IgA deposition in kidney allografts based on serological and histopathological evaluation of galactose-deficient IgA1 (Gd-IgA1). This study aimed to establish a classification system for IgA deposition in kidney allografts based on serological and histological evaluation of Gd-IgA1.

METHODS

This multicenter prospective study included 106 adult kidney transplant recipients in whom an allograft biopsy was performed. Serum and urinary Gd-IgA1 levels were investigated in 46 transplant recipients who were IgA-positive and classified into four subgroups according to the presence or absence of mesangial Gd-IgA1 (KM55 antibody) deposits and C3.

RESULTS

Minor histological changes without an acute lesion were observed in recipients with IgA deposition. Fourteen (30%) of the 46 IgA-positive recipients were KM55-positive and 18 (39%) were C3-positive. The C3 positivity rate was higher in the KM55-positive group. Serum and urinary Gd-IgA1 levels were significantly higher in KM55-positive/C3-positive recipients than in the other three groups with IgA deposition. Disappearance of IgA deposits was confirmed in 10 of 15 IgA-positive recipients in whom a further allograft biopsy was performed. The serum Gd-IgA1 level at the time of enrollment was significantly higher in recipients in whom IgA deposition continued than in those in whom it disappeared (p = 0.02).

CONCLUSIONS

The population with IgA deposition after kidney transplantation is serologically and pathologically heterogeneous. Serological and histological assessment of Gd-IgA1 is useful for identifying cases that should be carefully observed.

Characterization of patients with IgA nephropathy with and without associated minimal change disease

Introduction

Immunoglobulin A nephropathy (IgAN) presents various clinical manifestations and pathological phenotypes. Approximately 5% of patients with IgAN present with early onset nephrotic syndrome, mild mesangial lesions, and diffuse foot process effacement of podocytes, which resemble minimal change disease (MCD). These patients are defined as MCD-IgAN. Whether MCD-IgAN is a special type of IgAN or simply MCD accompanied by IgA deposition remains controversial.

Methods

A total of 51 patients diagnosed with MCD-IgAN at Beijing Anzhen Hospital from January 2010 to September 2022 were recruited. The clinical and pathological characteristics of IgA-MCD were analyzed. Patients with IgAN but without MCD (non-MCD-IgAN) and healthy participants were enrolled as controls. Galactose-deficient immunoglobulin A1 (Gd-IgA1) and complement C3 were detected both in the circulation and in renal tissues.

Results

We found that the levels of serum Gd-IgA1 were lower in participants with MCD-IgAN than in those with non-MCD-IgAN, but higher than in healthy participants. Gd-IgA1 was rarely deposited in the glomeruli of participants with MCD-IgAN, with a positive rate of only 13.7% (7/51); in contrast, the positive rate in participants with non-MCD-IgAN was 82.4% (42/51). Among renal Gd-IgA1-positive patients, Gd-IgA1 and immunoglobulin A (IgA) colocalized along the glomerular mesangial and capillary areas. Interestingly, we found that the circulating levels of complement C3 were significantly higher in participants with MCD-IgAN than in participants with non-MCD-IgAN. In addition, the intensity of C3c in glomeruli in participants with MCD-IgAN was significantly weaker than in participants with non-MCD-IgAN.

Conclusions

Our study suggests that, in MCD-IgAN, most of the IgA that is deposited on glomeruli is not the same pathogenic Gd-IgA1 as found in general IgAN. Complement activation both in the circulation and in the renal locality was much weaker in MCD-IgAN than in non-MCD-IgAN. Our study suggests that IgAN with MCD might be MCD with coincidental IgA deposition.

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.

IgA vasculitis with transient glomerular hematuria, diarrhea, and pericarditis following COVID-19 mRNA vaccination in a young patient with possible pre-existing ulcerative colitis

Exacerbations or de novo autoimmune/autoinflammatory disease have been reported after COVID-19 vaccination. A young male presented with cutaneous IgA vasculitis with glomerular hematuria, diarrhea and pericarditis following his second COVID-19 mRNA vaccination. He also showed positivity for proteinase 3 anti-neutrophil cytoplasmic antibody (PR3-ANCA) and anti-cardiolipin antibody. Skin biopsy was compatible to IgA vasculitis. His purpura subsided and hematuria spontaneously disappeared. Treatment with anti-inflammatory medications and prednisolone resolved the pericarditis. He had a history of persistent diarrhea, and colonic biopsies showed possible ulcerative colitis without vasculitis. Kidney biopsy after prednisolone therapy revealed minor glomerular abnormalities without any immune reactants and did not show vasculitis. After prednisolone treatment, PR3-ANCA decreased in a medium degree despite of improvement of symptoms and inflammatory data, suggesting that his PR3-ANCA may be associated with ulcerative colitis. The cause of the transient glomerular hematuria was unclear, however, it might be caused by focal glomerular active lesions (glomerular vasculitis) due to vaccine-induced IgA vasculitis with nephritis. This case highlights that COVID-19 mRNA vaccination can activate multiple autoimmune/autoinflammatory systems. The conditions might help us better understand the mutual mechanisms of the relevant disorders.

Current understanding of IgA antibodies in the pathogenesis of IgA nephropathy

Immunoglobulin A (IgA) is the most abundant isotype of antibodies, provides a first line of defense at mucosal surfaces against pathogens, and thereby contributes to mucosal homeostasis. IgA is generally considered as a non-inflammatory antibody because of its main function, neutralizing pathogenic virus or bacteria. Meanwhile, IgA can induce IgA-mediated diseases, such as IgA nephropathy (IgAN) and IgA vasculitis. IgAN is characterized by the deposition of IgA and complement C3, often with IgG and/or IgM, in the glomerular mesangial region, followed by mesangial cell proliferation and excessive synthesis of extracellular matrix in glomeruli. Almost half a century has passed since the first report of patients with IgAN; it remains debatable about the mechanism how IgA antibodies selectively bind to mesangial region-a hallmark of IgAN-and cause glomerular injuries in IgAN. Previous lectin- and mass-spectrometry-based analysis have revealed that IgAN patients showed elevated serum level of undergalactosylated IgA1 in O-linked glycans of its hinge region, called galactose-deficient IgA1 (Gd-IgA1). Thereafter, numerous studies have confirmed that the glomerular IgA from IgAN patients are enriched with Gd-IgA1; thus, the first hit of the current pathogenesis of IgAN has been considered to increase circulating levels of Gd-IgA1. Recent studies, however, demonstrated that this aberrant glycosylation alone is not sufficient to disease onset and progression, suggesting that several additional factors are required for the selective deposition of IgA in the mesangial region and induce nephritis. Herein, we discuss the current understanding of the characteristics of pathogenic IgA and its mechanism of inducing inflammation in IgAN.

Kidney biopsy diagnosis in childhood in the Norwegian Kidney Biopsy Registry and the long-term risk of kidney replacement therapy: a 25-year follow-up

BACKGROUND

There is scarce information on biopsy-verified kidney disease in childhood and its progression to chronic kidney disease stage 5 (CKD 5). This study aims to review biopsy findings in children, and to investigate risk of kidney replacement therapy (KRT).

METHODS

We conducted a retrospective long-term follow-up study of children included in the Norwegian Kidney Biopsy Registry (NKBR) and in the Norwegian Renal Registry (NRR) from 1988 to 2021.

RESULTS

In total, 575 children with a median (interquartile range, IQR) age of 10.7 (6.1 to 14.1) years were included, and median follow-up time (IQR) after kidney biopsy was 14.3 (range 8.9 to 21.6) years. The most common biopsy diagnoses were minimal change disease (MCD; n = 92), IgA vasculitis nephritis (IgAVN; n = 76), IgA nephropathy (n = 63), and focal and segmental glomerulosclerosis (FSGS; n = 47). In total, 118 (20.5%) of the biopsied children reached CKD 5, median (IQR) time to KRT 2.3 years (7 months to 8.4 years). Most frequently, nephronophthisis (NPHP; n = 16), FSGS (n = 30), IgA nephropathy (n = 9), and membranoproliferative glomerulonephritis (MPGN; n = 9) led to KRT.

CONCLUSIONS

The risk of KRT after a kidney biopsy diagnosis is highly dependent on the diagnosis. None of the children with MCD commenced KRT, while 63.8% with FSGS and 100% with NPHP reached KRT. Combining data from kidney biopsy registries with registries on KRT allows for detailed information concerning the risk for later CKD 5 after biopsy-verified kidney disease in childhood. A higher resolution version of the Graphical abstract is available as Supplementary information.

Glomerular Galactose-Deficient IgA1(KM55) Positive May Predict Poorer Prognosis in Coexisting Primary Membranous Nephropathy and IgA Nephropathy Patients

Primary membrane nephropathy (PMN) and IgA nephropathy (IgAN) are the most common glomerular diseases in China. Because of different pathogenesis, prognosis is significantly different. When the two diseases coexist (PMN/IgAN), the clinicopathological manifestations and prognosis remain unclear. In the present study, we analyzed the clinicopathological characteristics of PMN/IgAN patients, with only IgA deposition (PMN/IgA deposition) patients as controls. Galactose-deficient IgA1(KM55) and M-type Phospholipase A2 Receptor(PLA2R), both in circulation and renal tissues, were detected. Furthermore, prognosis of PMN/IgAN was explored. We found that PMN/IgAN also had some clinical features of IgAN in addition to PMN, such as higher serum albumin, along with a similar heavy proteinuria and lower titers of serum anti-PLA2R antibody. The positive rate of glomerular KM55 in PMN/IgAN was 23.5% (20/85), and 0% (0/29) in PMN/IgA deposition. Among those glomerular KM55 positive patients, KM55 and IgA colocalized mainly along the glomerular mesangial and capillary areas. Unfortunately, there was no significant difference in serum level of Gd-IgA1 between KM55+ and KM55- subgroups in PMN/IgAN patients, similar to the PMN/IgA deposition group. Notably, glomerular KM55 positive may predict a poorer prognosis in PMN/IgAN patients. In conclusion, our study suggested that, when glomerular KM55 staining was positive, this special coexisting PMN/IgAN disorder was prone to have more characteristics of IgAN besides PMN, and may predict poorer prognosis, while the mechanism requires further investigation.

Landscape of intestinal microbiota in patients with IgA nephropathy, IgA vasculitis and Kawasaki disease

Objective

To explore the common differential flora of IgAN, Kawasaki disease and IgA vasculitis by screening and analyzing the differential intestinal flora between the three disease groups of IgAN, Kawasaki disease and IgA vasculitis and their healthy controls.

Methods

Papers on 16srRNA sequencing-related intestinal flora of IgAN, Kawasaki disease and IgA vasculitis were searched in databases, the literature was systematically collated and analysed, the original data was download from the relevant databases, and then the operational taxonomic unit and species classification analysis were performed. Besides, Alpha diversity analysis and Beta diversity analysis were performed to screen for IgAN, Kawasaki disease and I1gA vasculitis groups and finally compare the common intestinal differential flora among the three groups.

Results

Among the common differential flora screened, Lachnospiracea_incertae_sedis was lower in both the IgAN and Kawasaki disease groups than in the respective healthy controls; Coprococcus was low in the IgAN group but high in the IgA vasculitis group. Fusicatenibacter was lower in both the Kawasaki disease and IgA vasculitis groups than in their respective healthy controls, and Intestinibacter was low in the Kawasaki disease group, but its expression was high in the IgA vasculitis group.

Conclusion

The dysbiosis of the intestinal flora in the three groups of patients with IgAN, Kawasaki disease and IgA vasculitis, its effect on the immunity of the organism and its role in the development of each disease group remain unclear, and the presence of their common differential flora may further provide new ideas for the association of the pathogenesis of the three diseases.

Development and validation of diagnostic models for immunoglobulin A nephropathy based on gut microbes

Background

Immunoglobulin A nephropathy (IgAN) is a highly prevalent glomerular disease. The diagnosis potential of the gut microbiome in IgAN has not been fully evaluated. Gut microbiota, serum metabolites, and clinical phenotype help to further deepen the understanding of IgAN.

Patients and methods

Cohort studies were conducted in healthy controls (HC), patients of IgA nephropathy (IgAN) and non-IgA nephropathy (n_IgAN). We used 16S rRNA to measure bacterial flora and non-targeted analysis methods to measure metabolomics; we then compared the differences in the gut microbiota between each group. The random forest method was used to explore the non-invasive diagnostic value of the gut microbiome in IgAN. We also compared serum metabolites and analyzed their correlation with the gut microbiome.

Results

The richness and diversity of gut microbiota were significantly different among IgAN, n_IgAN and HC patients. Using a random approach, we constructed the diagnosis model and analysed the differentiation between IgAN and n_IgAN based on gut microbiota. The area under the receiver operating characteristic curve for the diagnosis was 0.9899. The metabolic analysis showed that IgAN patients had significant metabolic differences compared with HCs. In IgAN, catechol, l-tryptophan, (1H-Indol-3-yl)-N-methylmethanamine, and pimelic acid were found to be enriched. In the correlation analysis, l-tryptophan, blood urea nitrogen and Eubacterium coprostanoligenes were positively correlated with each other.

Conclusion

Our study demonstrated changes in the gut microbiota and established models for the non-invasive diagnosis of IgAN from HC and n_IgAN. We further demonstrated a close correlation between the gut flora, metabolites, and clinical phenotypes of IgAN. These findings provide further directions and clues in the study of the mechanism of IgAN.

Associations of left renal vein entrapment with IgA nephropathy and Henoch-Schönlein purpura nephritis

Objectives

The aims of the study were to identify whether left renal vein (LRV) entrapment was more prevalent in IgA nephropathy (IgAN) and Henoch–Schönlein purpura nephritis (HSPN) compared with other types of renal diseases, and the association of LRV entrapment with glomerular incidental IgA and galactose-deficient-IgA1 (Gd-IgA1) deposition.

Methods

A total of 797 patients with biopsy-proven kidney diseases have been screened for LRV entrapment by color Doppler ultrasound, and the prevalence of LRV entrapment in different types of renal diseases were then analyzed. Propensity score matching analysis was used to adjust for age, gender, and body mass index. Immunostaining of Gd-IgA1 with KM55 was performed in paraffin-embedded sections of renal biopsy specimens.

Results

LRV entrapment was diagnosed in 47 patients (6%) with several kinds of renal diseases in our cohort. A total of 32 (68%) LRV entrapments were combined with expanded IgAN (idiopathic IgAN and HSPN). The prevalence of LRV entrapment in expanded IgAN was significantly higher than that in non-expanded IgAN (17 vs. 2%, p < 0.001), even after adjustment for age, gender, and body mass index by propensity score matching analysis (13 vs. 2%, p < 0.001). Removing expanded IgAN and LN, glomerular incidental IgA deposition was observed to be significantly more common in patients with LRV entrapment compared with patients without it (43 vs. 9%, p < 0.001). Furthermore, in glomerular diseases with incidental IgA deposits, significantly much larger proportion of patients with LRV entrapment were positive for glomerular Gd-IgA1 in contrast to patients without LRV entrapment (5/5 vs. 5/17, p = 0.01).

Conclusions

LRV entrapment coexisted with several kinds of renal diseases, with a significantly higher prevalence in patients with idiopathic IgAN and HSPN. In patients of LN and IgAN-unrelated disease with LRV entrapment, glomerular IgA and Gd-IgA1 deposition was more common compared with patients without LRV entrapment.

Galactose-deficient IgA1 is Involved in IgA Deposition in Renal Grafts Biopsied One Hour after Kidney Transplantation

Objective Asymptomatic renal immunoglobulin A (IgA) deposition occurs in healthy subjects, but its etiologic role in disease is unclear. Galactose-deficient IgA1 (Gd-IgA1) is involved in the pathogenesis of IgA nephropathy. We investigated Gd-IgA1 deposition in transplanted kidneys that were considered healthy showing subclinical latent IgA deposition one hour after transplantation. Methods A total of 723 transplanted kidney specimens biopsied 1 h after kidney transplantation from 2009 to 2016 at Nagoya Red Cross Hospital were examined. A total of 81 cases of IgA deposition were extracted, and 41 were ultimately studied. Double immunofluorescence staining for Gd-IgA1 and IgA was conducted to investigate the role of Gd-IgA1 in subclinical IgA deposition. Results Light microscopy findings for the 41 cases indicated only minor glomerular abnormalities. Immunofluorescence analyses revealed that all cases were positive for IgA. C3, IgG, and IgM positivity rates were 78.0%, 7.3%, and 60.9%, respectively. All 41 cases were positive for Gd-IgA1, which merged with IgA deposition in immunofluorescence double staining. IgA disappeared in 26 of 40 cases (65.0%) 1 year after kidney transplantation. In contrast, IgA redeposition was observed in three cases. Conclusion Gd-IgA1 was demonstrated in all transplanted kidneys, with latent IgA deposition noted in otherwise healthy kidneys. Deposition of Gd-IgA1 might indicate the initial stage of IgA nephropathy; however, additional factors, such as IgG deposition, are required for the ultimate development of IgA nephropathy.

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.

IgA vasculitis update: Epidemiology, pathogenesis, and biomarkers

Immunoglobulin A vasculitis (IgAV), formerly known as Henoch-Schönlein purpura, is the most common systemic vasculitis in children, characterized by diverse clinical manifestations with a wide spectrum ranging from isolated cutaneous vasculitis to systemic involvement. The incidence of IgAV is geographically and ethnically variable, with a prevalence in autumn and winter, suggesting a driving role that genetic and environmental factors play in the disease. Although IgAV has a certain degree of natural remission, it varies widely among individuals. Some patients can suffer from severe renal involvement and even progress to end-stage renal disease. Its pathogenesis is complex and has not been fully elucidated. The formation of galactose-deficient IgA1 (Gd-IgA1) and related immune complexes plays a vital role in promoting the occurrence and development of IgAV nephritis. In addition, neutrophil activation is stimulated through the binding of IgA to the Fc alpha receptor I expressed on its surface, resulting in systemic vascular inflammation and tissue damage. Starting from the epidemiological characteristics, this article will review the role of immunological factors such as Gd-IgA1, autoantibodies, circulating immune complexes, complement system, cellular immunization, and the contributions of environmental and genetic factors in the pathogenesis of IgAV, and conclude with the major biomarkers for IgAV.

Advances in IgA glycosylation and its correlation with diseases

Immunoglobulin A (IgA) is the most abundant immunoglobulin synthesized in the human body. It has the highest concentration in the mucosa and is second only to IgG in serum. IgA plays an important role in mucosal immunity, and is the predominant antibody used to protect the mucosal surface from pathogens invasion and to maintain the homeostasis of intestinal flora. Moreover, The binding IgA to the FcαRI (Fc alpha Receptor I) in soluble or aggregated form can mediate anti- or pro- inflammatory responses, respectively. IgA is also known as one of the most heavily glycosylated antibodies among human immunoglobulins. The glycosylation of IgA has been shown to have a significant effect on its immune function. Variation in the glycoform of IgA is often the main characteration of autoimmune diseases such as IgA nephropathy (IgAN), IgA vasculitis (IgAV), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). However, compared with the confirmed glycosylation function of IgG, the pathogenic mechanism of IgA glycosylation involved in related diseases is still unclear. This paper mainly summarizes the recent reports on IgA’s glycan structure, its function, its relationship with the occurrence and development of diseases, and the potential application of glycoengineered IgA in clinical antibody therapeutics, in order to provide a potential reference for future research in this field.

Zonulin, as a marker of intestinal permeability, is elevated in IgA nephropathy and IgA vasculitis with nephritis

Background

Immunoglobulin A nephropathy (IgAN) and IgA vasculitis with nephritis (IgAV-N) are considered related diseases and share some similar clinicopathologic phenotypes. Elevated circulating galactose-deficient IgA1 (Gd-IgA1)-containing immune complexes and mucosal immunity were associated with the pathogenesis of IgAN and IgAV-N. Recently, studies have identified that the zonulin level, as a modulator of intestinal permeability, is significantly elevated in several inflammatory and autoimmune-related diseases. However, whether zonulin also plays a role in IgAN and IgAV-N is not clear.

Methods

A total of 73 IgAV-N patients, 68 IgAN patients and 54 healthy controls were assessed for circulating zonulin and Gd-IgA1 levels by enzyme-linked immunosorbent assay. The diagnostic efficiency of the combination of zonulin with Gd-IgA1 was evaluated by the area under the receiver operating characteristic curve (AUC) and integrated discrimination improvement (IDI) analysis.

Results

Compared with healthy controls, we found that both IgAV-N and IgAN patients had elevated zonulin and Gd-IgA1 levels (P < .001). Additionally, patients with IgAV-N presented with even higher circulating zonulin levels than patients with IgAN (P = .020). The addition of zonulin to Gd-IgA1 showed better predictive performance than Gd-IgA1 alone in the diagnosis of both IgAN and IgAV-N, as illustrated by a significantly increased AUC (IgAN: 0.805 versus 0.708, P = .0021; IgAV-N: 0.886 versus 0.673, P < .001) and significant IDI (IgAN: IDI 0.136, P < .001; IgAV-N: IDI 0.281, P < .001).

Conclusion

Elevated circulating zonulin levels were detected in both patients with IgAV-N and those with IgAN. Combined detection of circulating zonulin and Gd-IgA1 is recommended as a noninvasive diagnostic biomarker for IgAV-N and IgAN.

Metagenomics-based systematic analysis reveals that gut microbiota Gd-IgA1-associated enzymes may play a key role in IgA nephropathy

Background: IgA nephropathy (IgAN) is the most common type of glomerulonephritis in Asia. Its pathogenesis involves higher expression of galactose-deficient IgA1 (Gd-IgA1) and dysregulated intestinal mucosal immunity. The objective of this study was to explore whether specific gut microbiota and associated enzymes affect Gd-IgA1 in IgAN.

Methods: This study carried out shotgun metagenomic sequencing with Illumina on fecal samples collected from 20 IgAN patients (IgAN group) and 20 healthy controls (HCs group) who were recruited from January 2016 to December 2018 at the Second Clinical College of Guangzhou University of Chinese Medicine. Differences analysis in gut microbiota was performed to determine the overall microbiota composition, the representative enterotypes, and the microbiota abundance. Correlations between gut microbiota and clinical indicators were assessed by Spearman’s analysis. Moreover, the functional prediction of microbial communities and the quantitative calculation of enzymes encoded by microbiome were performed using the MetaCyc pathway and the bioBakery three platform, respectively.

Results:Bacteroides plebeius and Bacteroides vulgatus levels were higher, while Prevotella copri and Alistipes putredinis levels were lower in the IgAN group compared to HCs group. Enterotype I characterized by Bacteroides was closely related to the IgAN patients. Moreover, Bacteroides fragilis, Flavonifractor plautii and Ruminococcus gnavus were characteristic bacteria enriched in IgAN patients. Spearman’s correlation analysis found that Eggerthella lenta and Ruminococcus bromii were positively correlated with urine protein-creatinine ratio, while Ruminococcus gnavus showed a direct association with red blood cells in urine, and Bacteroides vulgatus and Ruminococcus gnavus were positively correlated with eGFR. These results indicated that intestinal dysbacteriosis occurred in IgAN patients and was associated with clinical and biochemical features. In addition, MetaCyc pathway analysis predicted microbiota-related metabolic pathways, including the biosynthesis of amino acids and glycans, were associated with the IgAN group. Microbial enzymes analysis highlighted that Gd-IgA1-associated α-galactosidase and α-N-acetyl-galactosaminidase secreted by Flavonifractor plautii were enriched in IgAN patients.

Conclusion: These findings suggested that α-galactosidase and α-N-acetyl-galactosaminidase secreted by Flavonifractor plautii might be related to the production of Gd-IgA1, indicating that enzymes originated from abnormal intestinal microbiota may contribute to the production of Gd-IgA1 and play an important role in the pathogenesis of IgAN.

IL-6 and its role in IgA nephropathy development

IL-6 is considered one of the well characterized cytokines exhibiting homeostatic, pro- and anti-inflammatory activities, depending on the receptor variant and the induced intracellular cis- or trans-signaling responses. IL-6-activated pathways are involved in the regulation of cell proliferation, survival, differentiation, and cell metabolism changes. Deviations in IL-6 levels or abnormal response to IL-6 signaling are associated with several autoimmune diseases including IgA nephropathy (IgAN), one of most frequent primary glomerulonephritis worldwide. IgAN is associated with increased plasma concentration of IL-6 and increased plasma concentration of aberrantly galactosylated IgA1 immunoglobulin (Gd-IgA1). Gd-IgA1 is specifically recognized by autoantibodies, leading to the formation of circulating immune complexes (CIC) with nephritogenic potential, since CIC deposited in the glomerular mesangium induce mesangial cells proliferation and glomerular injury. Infection of the upper respiratory or digestive tract enhances IL-6 production and in IgAN patients is often followed by the macroscopic hematuria. This review recapitulates general aspects of IL-6 signaling and summarizes experimental evidences about IL-6 involvement in the etiopathogenesis of IgA nephropathy through the production of Gd-IgA1 and regulation of mesangial cell proliferation.

Gut Dysbiosis and Intestinal Barrier Dysfunction Promotes IgA Nephropathy by Increasing the Production of Gd-IgA1

Background

Immunoglobulin A nephropathy (IgAN) is the most common type of primary glomerular disease in adults worldwide. Several studies have reported that galactose-deficient IgA1 (Gd-IgA1) is involved in the pathogenesis of IgAN.

Methods

Thirty-five patients with IgAN diagnosed with renal biopsy for the first time served as the experimental group, who were hospitalized in our department. Twenty normal healthy cases in the physical examination center of our hospital served as the control group. Then the levels of Gd-IgA1 in serum and urine, and intestinal mucosal barrier injury indexes [diamine oxidase (DAO), serum soluble intercellular adhesion molecule-1 (sICAM-1), D-lactate (D-LAC), and lipopolysaccharide (LPS)] and inflammatory factors [interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α)] in the serum samples were detected. Fecal samples were collected to detect intestinal microbiota using 16 s rDNA sequencing. Then, we assessed possible correlations among clinical and laboratory findings.

Results

In patients with IgAN, the levels of Gd-IgA1 both in the serum and urine were higher than that of the healthy control. Furthermore, urine Gd-IgA1 level was positively correlated with the serum creatinine level, 24 h urine protein, and M, S, and T parameters in the Oxford classification. ROC curve analysis showed that urine Gd-IgA1 has a greater diagnostic value (AUC = 0.9714, 95% CI, 0.932–1; P &lt; 0.0001) for IgAN. The best cutoff value for urine Gd-IgA1 was 0.745 ng·l/ml·μmol (sensitivity, 94%; specificity, 95%). The intestinal mucosal barrier damage indexes (DAO, sICAM-1, D-LAC, and LPS) were increased in the patients with IgAN, which were positively correlated with Gd-IgA1 levels (P &lt; 0.05) both in serum and urine. The levels of inflammatory factors in the patients with IgAN were increased. 16 s rDNA analysis showed that the intestinal microbiota in these patients was disordered compared to that observed in the healthy subjects. Actinobacteria, Bifidobacterium, Blautia, Bifidobacteriaceae, and Bifidobacteriales were decreased and Shigella was increased in IgAN. The decreased populations of these flora were negatively and significantly correlated with urine Gd-IgA1 and the levels of DAO, sICAM-1, D-LAC, and LPS.

Conclusion

The urine Gd-IgA1 levels may be a non-invasive biological marker for evaluating kidney injury in IgAN. Gut flora dysbiosis and intestinal barrier dysfunction may be involved in Gd-IgA1 expression.

Staphylococcus aureus Infection-Related Glomerulonephritis with Dominant IgA Deposition

Since 1995, when we reported the case of a patient with glomerulonephritis with IgA deposition that occurred after a methicillin-resistant Staphylococcus aureus (MRSA) infection, many reports of MRSA infection-associated glomerulonephritis have accumulated. This disease is being systematized as Staphylococcus infection-associated glomerulonephritis (SAGN) in light of the apparent cause of infection, and as immunoglobulin A-dominant deposition infection-related glomerulonephritis (IgA-IRGN) in light of its histopathology. This glomerulonephritis usually presents as rapidly progressive glomerulonephritis or acute kidney injury with various degrees of proteinuria and microscopic hematuria along with an ongoing infection. Its renal pathology has shown several types of mesangial and/or endocapillary proliferative glomerulonephritis with various degrees of crescent formation and tubulointerstitial nephritis. IgA, IgG, and C₃ staining in the mesangium and along the glomerular capillary walls have been observed on immunofluorescence examinations. A marked activation of T cells, an increase in specific variable regions of the T-cell receptor β-chain-positive cells, hypercytokinemia, and increased polyclonal immune complexes have also been observed in this glomerulonephritis. In the development of this disease, staphylococcal enterotoxin may be involved as a superantigen, but further investigations are needed to clarify the mechanisms underlying this disease. Here, we review 336 cases of IgA-IRGN and 218 cases of SAGN.

Efficacy and Safety of Tacrolimus in the Treatment of Pediatric Henoch-Schönlein Purpura Nephritis

BACKGROUND

Children with severe Henoch-Schönlein purpura nephritis (HSPN) may progress to end-stage renal disease without appropriate treatment.

OBJECTIVE

This study aimed to investigate the efficacy and safety of tacrolimus combined with glucocorticoids in the treatment of pediatric HSPN.

METHODS

A total of 87 HSPN patients with urinary protein ≥ 0.75 g/24 h received standard of care, including angiotensin II receptor blockers/angiotensin-converting enzyme inhibitors and glucocorticoids. Patients were divided into three groups and additionally received tacrolimus (n = 30), cyclophosphamide (n = 31), or mycophenolate mofetil (MMF) (n = 26). We monitored outcome measures, including proteinuria, hematuria, and renal function and analyzed the efficacy and side effects in each group.

RESULTS

At 2-month follow-up, the overall efficacy was 93.3%, 83.9%, and 61.5% for tacrolimus, cyclophosphamide, and MMF, respectively (P < 0.05). Urinary protein significantly decreased for all groups. Urinary red blood cell counts significantly decreased for patients treated with tacrolimus (P < 0.001) and cyclophosphamide (P < 0.05), whereas no significant decrease was seen for those receiving MMF (P = 0.09). Although urine β2-microglobulin significantly decreased following 2 months of treatment with all medications, efficacy was greater with tacrolimus than with cyclophosphamide and MMF (P < 0.001). Major adverse events were respiratory and urinary infections, with MMF having the highest infection rate. The cyclophosphamide group also experienced additional adverse events, including arrhythmia, hemorrhagic cystitis, leukocytosis, thrombocytopenia, and hyperglycemia.

CONCLUSIONS

These results indicate that tacrolimus is more effective at reducing proteinuria and hematuria and improving renal function, with relatively milder side effects, in the treatment of pediatric HSPN.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR2200055323, retrospectively registered on January 7, 2022.

Identification of Hub Genes and Therapeutic Agents for IgA Nephropathy Through Bioinformatics Analysis and Experimental Validation

Background

IgA nephropathy (IgAN) is the most common primary glomerular disease and the leading cause of the end-stage renal disease in the world. The pathogenesis of IgAN has not been well elucidated, and yet treatment is limited. High-throughput microarray has been applied for elucidating molecular biomarkers and potential mechanisms involved in IgAN. This study aimed to identify the potential key genes and therapeutics associated with IgAN using integrative bioinformatics and transcriptome-based computational drug repurposing approach.

Methods

Three datasets of mRNA expression profile were obtained from the gene expression omnibus database and differentially expressed genes (DEGs) between IgAN glomeruli and normal tissue were identified by integrated analysis. Gene ontology and pathway enrichment analyses of the DEGs were performed by R software, and protein-protein interaction networks were constructed using the STRING online search tool. External dataset and immunohistochemical assessment of kidney biopsy specimens were used for hub gene validation. Potential compounds for IgAN therapy were obtained by Connectivity Map (CMap) analysis and preliminarily verified in vitro. Stimulated human mesangial cells were collected for cell proliferation and cell cycle analysis using cell counting kit 8 and flow cytometry, respectively.

Results

134 DEGs genes were differentially expressed across kidney transcriptomic data from IgAN patients and healthy living donors. Enrichment analysis showed that the glomerular compartments underwent a wide range of interesting pathological changes during kidney injury, focused on anion transmembrane transporter activity and protein digestion and absorption mostly. Hub genes (ITGB2, FCER1G, CSF1R) were identified and verified to be significantly upregulated in IgAN patients, and associated with severity of renal lesions. Computational drug repurposing with the CMap identified tetrandrine as a candidate treatment to reverse IgAN hub gene expression. Tetrandrine administration significantly reversed mesangial cell proliferation and cell cycle transition.

Conclusion

The identification of DEGs and related therapeutic strategies of IgAN through this integrated bioinformatics analysis provides a valuable resource of therapeutic targets and agents of IgAN. Especially, our findings suggest that tetrandrine might be beneficial for IgAN, which deserves future research.

Glomerular deposition of galactose-deficient IgA1-containing immune complexes via glomerular endothelial cell injuries

BACKGROUND

Galactose-deficient IgA1 (Gd-IgA1) plays a crucial role in the development of IgA nephropathy (IgAN). However, the pathological role of Gd-IgA1-containing immune complexes (ICs) and the mechanism of deposition in the mesangial region remain unclear.

METHODS

To examine deposition of Gd-IgA1-containing ICs in the mesangial region through glomerular endothelial cell injury, we evaluated the alteration of renal microvascular endothelial glycocalyx in nude mice injected with Gd-IgA1-IgG ICs. Human renal glomerular endothelial cells (HRGECs) were used to assess the potential capacity of Gd-IgA1-IgG ICs to activate endothelial cells.

RESULTS

Nude mice injected with Gd-IgA1-containing ICs showed podocyte and endothelial cell injuries with IgA, IgG, and C3 depositions in glomerular capillaries and the mesangium. Moreover, albuminuria and hematuria were induced. Real-time glycocalyx imaging showed that renal microvascular glycocalyx was decreased immediately after injection of Gd-IgA1-containing ICs and then mesangial IgA deposition was increased. After coculture of Gd-IgA1-containing ICs with HRGECs, mRNA expression levels of endothelial adhesion molecules and proinflammatory mediators were upregulated significantly.

CONCLUSION

Gd-IgA1-IgG ICs had a high affinity for glomerular endothelial cells, which resulted in glomerular filtration barrier dysfunction mediated by glycocalyx loss. Furthermore, Gd-IgA1-IgG ICs accelerated production of adhesion factors and proinflammatory cytokines in glomerular endothelial cells. The glomerular endothelial cell injury induced by Gd-IgA1-containing ICs may enhance the permeability of immunoglobulins in the mesangial region and subsequent inflammatory responses in the pathogenesis of IgAN.

Arteriolar hyalinosis and renal outcomes in patients with immunoglobulin A nephropathy

BACKGROUND

The relationship between arteriolar hyalinosis and renal progression in immunoglobulin A nephropathy (IgAN) is not fully understood. We aimed to investigate the clinicopathological features and outcomes of IgAN with or without arteriolar hyalinosis.

METHODS

A total of 762 diagnosed with IgAN patients were retrospectively analyzed. We classified IgAN patients into two groups with or without arteriolar hyalinosis. Then, the clinicopathological characteristics of the two groups were compared. We used Kaplan-Meier survival analysis to compare the composite kidney outcome of the two groups and applied multivariate Cox regression analyses to test the association between arteriolar hyalinosis and composite kidney outcome.

RESULTS

Overall, 412 (54.1%) patients had arteriolar hyalinosis, including 173 patients diagnosed with hypertension. IgAN patients with arteriolar hyalinosis were older and had higher proteinuria, urea, uric acid, and blood pressure, while lower eGFR than those without arteriolar hyalinosis. Subgroup analysis showed similar results in IgAN patients with hypertension. Kaplan-Meier survival analysis showed that IgAN patients with arteriolar hyalinosis had worse composite kidney outcome than those without arteriolar hyalinosis. In addition, subgroup analysis revealed that patients with hypertension have worse composite kidney outcome than those without hypertension. Multivariate Cox regression analyses confirm that arteriolar hyalinosis (HR 2.57; 95% CI 1.41-4.69; p = 0.002) is an independent risk factor for renal prognosis in IgAN patients.

CONCLUSIONS

Our study demonstrated that arteriolar hyalinosis is a common vascular lesion in IgAN patients. Arteriolar hyalinosis connects closely with hypertension, and arteriolar hyalinosis is an independent risk factor for renal prognosis in patients with IgAN.

Galactose-Deficient IgA1 as a Candidate Urinary Marker of IgA Nephropathy

In patients with IgA nephropathy (IgAN), circulatory IgA1 and IgA1 in the mesangial deposits contain galactose-deficient IgA1 (Gd-IgA1). Some of the Gd-IgA1 from the glomerular deposits is excreted in the urine and thus urinary Gd-IgA1 may represent a disease-specific marker. We recruited 338 Japanese biopsy-proven IgAN patients and 120 patients with other renal diseases (disease controls). Urine samples collected at the time of renal biopsy were used to measure Gd-IgA1 levels using a specific monoclonal antibody (KM55 mAb). Urinary Gd-IgA1 levels were significantly higher in patients with IgAN than in disease controls. Moreover, urinary Gd-IgA1 was significantly correlated with the severity of the histopathological parameters in IgAN patients. Next, we validated the use of urinary Gd-IgA1 levels in the other Asian cohorts. In the Korean cohort, urinary Gd-IgA1 levels were also higher in patients with IgAN than in disease controls. Even in Japanese patients with IgAN and trace proteinuria (less than 0.3 g/gCr), urinary Gd-IgA1 was detected. Thus, urinary Gd-IgA1 may be an early disease-specific biomarker useful for determining the disease activity of IgAN.

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.

IgA Nephropathy with Gross Hematuria Following COVID-19 mRNA Vaccination

A 28-year-old woman experienced gross hematuria after the administration of the second dose of an messenger ribonucleic acid (mRNA) vaccine (BNT162b2). She was diagnosed with Immunogloblin A nephropathy (IgAN) by a renal biopsy two weeks after vaccination, which revealed a mild increase in mesangial cells and a matrix with co-depositions of galactose-deficient IgA1 and C3 in the mesangial region. The gross hematuria and proteinuria gradually improved without any medication, suggesting that immune activation by the mRNA vaccine may not elicit continuous disease progression of IgAN. Thus, further studies investigating the relationship between mRNA vaccines against COVID-19 and the progression of IgAN should be conducted.

Meta-Analysis of the Effectiveness and Safety of Glucocorticoid for the Treatment of IgA Kidney Disease

Purpose

To explore the effect of glucocorticoid on immune globulin A (IgA) nephropathy by meta-analysis.

Method

Search the data and literature libraries of ScienceDirect, EBSCO, Wiley, PubMed, CBMdisc, and CNKI and collect the literature on the treatment of IgA nephropathy with glucocorticoids as randomized controlled trials published at home and abroad from 1995 to 2021. The standardized mean difference (SMD) and 95% confidence interval (CI) were calculated by fixed-effects model. RevMan 5.0 software was used for meta-analysis of the subgroups of overall curative effect, different degree of proteinuria, different course of treatment, different creatinine level, and combined ACEI.

Result

① The overall efficacy of glucocorticoid in the treatment of IgA nephropathy was better than that in the control group (P = 0.00001). ② The efficacy of glucocorticoid treatment in patients with IgA nephropathy with proteinuria greater than 1.50 g/d and less than 1.50 g/d was better than that in the control group (P < 0.01). ③ For IgA nephropathy patients with serum creatinine less than 1.50 mg/dl, the curative effect of glucocorticoid treatment was better than that of the control group (P < 0.01). ④ The effects of short-term treatment (<1 year) and long-term treatment (≥1 year) with glucocorticoid were better than those in the control group (P < 0.01). ⑤ The effect of hormone combined with ACEI drugs on IgA nephropathy was more significant (P < 0.01).

Conclusion

The overall efficacy of glucocorticoid in the treatment of IgA nephropathy is accurate. Hormone treatment is effective for different degrees of IgA nephropathy. Considering that there is no significant effect on the efficacy of different courses of treatment, it is suggested that the course of hormone treatment can be appropriately shortened. Hormone combined with angiotensin-converting enzyme inhibitors (ACEI) can reduce proteinuria more effectively than ACEI drugs alone.

The Usefulness of Vanin-1 and Periostin as Markers of an Active Autoimmune Process or Renal Fibrosis in Children with IgA Nephropathy and IgA Vasculitis with Nephritis-A Pilot Study

This study aimed to evaluate the usefulness of vanin-1 and periostin in urine as markers of the autoimmune process in kidneys and renal fibrosis in IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN). From a group of 194 patients from the Department of Pediatrics and Nephrology, who were included in the Polish Pediatric Registry of IgAN and IgAVN, we qualified 51 patients (20 with IgAN and 31 with IgAVN) between the ages of 3 and 17, diagnosed based on kidney biopsy, for inclusion in the study. All of the patients received glucocorticosteroids, immunosuppressive drugs, or renoprotective therapy. The control group consisted of 18 healthy individuals. The concentration of vanin was significantly higher in the IgAN and IgAVN groups than in the control group. The concentration of vanin/creatinine correlates positively with the level of IgA and negatively with the serum level of C3 at the end of the observation. Urinary vanin-1 concentration may be useful as a marker of the active autoimmune process in IgAN and IgAVN in children, but the study needs confirmation on a larger group of children, along with evaluation of the dynamics of this marker. Urinary periostin is not a good marker for children with IgAN and IgAVN, especially in stage 1 and 2 CKD.

A case of pathologically confirmed streptococcal infection-related IgA vasculitis with associated glomerulonephritis and leukocytoclastic cutaneous vasculitis

We report the case of an 80 year-old woman who developed bilateral lower extremity purpura and renal impairment with proteinuria a few days after a transient fever (day 0). High levels of both anti-streptolysin-O antibody (ASO) and anti-streptokinase antibody (ASK), as well as low levels of coagulation factor XIII in serum were noted. Skin biopsy was performed and showed a leukocytoclastic vasculitis with deposition of IgA and C3 in the cutaneous small vessels, indicating IgA vasculitis in the skin. After initiation of oral prednisolone, the skin lesions showed significant improvement. However, renal function and proteinuria gradually worsened from day 12. Kidney biopsy was performed on day 29, which demonstrated a necrotizing and crescentic glomerulonephritis with mesangial deposition of IgA and C3. In addition, the deposition of galactose-deficient IgA1 (Gd-IgA1) was positive on glomeruli and cutaneous small vessels, indicating that the purpura and glomerulonephritis both shared the same Gd-IgA1-related pathogenesis. In addition, the association between the acute streptococcal infection and the IgA vasculitis was confirmed by the deposition of nephritis-associated plasmin receptor (NAPlr) in glomeruli. The patient was treated with steroid pulse and intravenous cyclophosphamide, in addition to the oral prednisolone treatment. Renal function and proteinuria gradually improved, but did not completely recover, as is typically seen with courses of IgA vasculitis in the elderly. In this case, the streptococcal infectionrelated IgA vasculitis was confirmed pathologically by the deposition of both NAPlr and Gd-IgA1 in glomeruli, as well as Gd-IgA1 in the cutaneous small vessels.

Lipid metabolism contribute to the pathogenesis of IgA Vasculitis

Background and objectives

The underlying mechanism of IgA vasculitis (IgAV) and IgA vasculitis with nephritis (IgAVN) remains unclear. Therefore, there are no accurate diagnostic methods. Lipid metabolism is related to many immune related diseases, so this study set out to explore the relationship of lipids and IgAV and IgAVN.

Methods

Fifty-eighth patients with IgAV and 28 healthy controls were recruited, which were divided into six separate pools to investigate the alterations of serum lipids according to the clinical characteristics: healthy controls group (HCs) and IgAV group (IgAVs), IgAVN group (IgAV-N) and IgAV without nephritis group (IgAV-C), initial IgAV group (IgAV0) and IgAV in treatment with glucocorticoids group (IgAV1).

Results

31 identified lipid ions significantly changed in IgAVs with p < 0.05, variable importance of the projection (VIP) > 1 and fold change (FC) > 1.5. All these 31 lipid ions belong to 6 classes: triacylglycerols (TG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine, ceramide, and lysophosphatidylcholine. TG (16:0/18:1/22:6) +NH4 over 888875609.05, PC (32:1) +H over 905307459.90 and PE (21:4)-H less than 32236196.59 increased the risk of IgAV significantly (OR>1). PC (38:6) +H was significantly decreased (p < 0.05, VIP>1 and FC>1.5) in IgAVN. PC (38:6) less than 4469726623 conferred greater risks of IgAV (OR=45.833, 95%CI: 6.689~341.070).

Conclusion

We suggest that lipid metabolism may affect the pathogenesis of IgAV via cardiovascular disease, insulin resistance, cell apoptosis, and inflammation. The increase of TG(16:0/18:1/22:6) + NH4, and PC(32:1) + H as well as PE (21:4)-H allow a good prediction of IgAV. PE-to-PC conversion may participate in the damage of kidney in IgAV. PC (38:6) + H may be a potential biomarker for IgAVN.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13000-021-01185-1.

Galactose-Deficient IgA1 B cells in the Circulation of IgA Nephropathy Patients Carry Preferentially Lambda Light Chains and Mucosal Homing Receptors

Background: Immunoglobulin A nephropathy (IgAN) primary glomerulonephritis is characterized by the deposition of circulating immune complexes (CIC) composed of polymeric (p)IgA1 molecules with altered O-glycans (Gd-IgA1) and anti-glycan antibodies in the kidney mesangium. The mesangial IgA deposits and serum IgA1 contain predominantly lambda (λ) light (L) chain, but the nature and origin of such IgA remains enigmatic Methods: We analyzed λ L chain expression in peripheral blood B cells of 30 IgAN patients, 30 healthy controls (HC), and 18 membranous nephropathy patients selected as disease controls (Non-IgAN). Results: In comparison to HC and Non-IgAN, in peripheral blood surface/membrane bound (mb)-Gd-IgA1⁺ cells from IgAN patients express predominantly λ L chain. In contrast, total mb-IgA⁺, mb-IgG⁺, and mb-IgM⁺ cells were preferentially positive for kappa (κ) L chain, in all analyzed groups. Although minor in comparison to κ L chain, λ L chain subsets of mb-IgG⁺, mb-IgM,⁺ and mb-IgA⁺ cells were significantly enriched in IgAN in comparison to Non-IgAN and/or HC. In contrast to HC, the peripheral blood of IgAN patients was enriched for λ⁺ mb-Gd-IgA1,⁺ CCR10,⁺ and CCR9⁺ cells, which preferentially home to the upper respiratory and digestive tract, respectively. Furthermore, we observed that mb-Gd-IgA1⁺ cell populations comprise more CD138⁺ cells and plasmablasts (CD38⁺) in comparison to total mb-IgA⁺ cells. Conclusions: Peripheral blood of IgAN patients is enriched for migratory λ⁺ mb-GdIgA1⁺ B cells, with the potential to home to mucosal sites where Gd-IgA1 could be produced during local respiratory or digestive tract infections.