Streptococcal origin of a case of Henoch-Schoenlein purpura nephritis

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.

Angiotensin II and post-streptococcal glomerulonephritis

BACKGROUND

Post-streptococcal glomerulonephritis (PSGN) is a consequence of the infection by group A beta-hemolytic streptococcus. During this infection, various immunological processes generated by streptococcal antigens are triggered, such as the induction of antibodies and immune complexes. This activation of the immune system involves both innate and acquired immunity. The immunological events that occur at the renal level lead to kidney damage with chronic renal failure as well as resolution of the pathological process (in most cases). Angiotensin II (Ang II) is a molecule with vasopressor and pro-inflammatory capacities, being an important factor in various inflammatory processes. During PSGN some events are defined that make Ang II conceivable as a molecule involved in the inflammatory processes during the disease.

CONCLUSION

This review is focused on defining which reported events would be related to the presence of this hormone in PSGN.

Clinico-Pathogenic Similarities and Differences between Infection-Related Glomerulonephritis and C3 Glomerulopathy

Recently, the comprehensive concept of "infection-related glomerulonephritis (IRGN)" has replaced that of postinfectious glomerulonephritis (PIGN) because of the diverse infection patterns, epidemiology, clinical features, and pathogenesis. In addition to evidence of infection, hypocomplementemia particularly depresses serum complement 3 (C3), with endocapillary proliferative and exudative GN developing into membranoproliferative glomerulonephritis (MPGN); also, C3-dominant or co-dominant glomerular immunofluorescence staining is central for diagnosing IRGN. Moreover, nephritis-associated plasmin receptor (NAPlr), originally isolated from the cytoplasmic fraction of group A Streptococci, is vital as an essential inducer of C3-dominant glomerular injury and is a key diagnostic biomarker for IRGN. Meanwhile, "C3 glomerulopathy (C3G)", also showing a histological pattern of MPGN due to acquired or genetic dysregulation of the complement alternative pathway (AP), mimics C3-dominant IRGN. Initially, C3G was characterized by intensive "isolated C3" deposition on glomeruli. However, updated definitions allow for glomerular deposition of other complement factors or immunoglobulins if C3 positivity is dominant and at least two orders of magnitude greater than any other immunoreactant, which makes it challenging to quickly distinguish pathomorphological findings between IRGN and C3G. As for NAPlr, it was demonstrated to induce complement AP activation directly in vitro, and it aggravates glomerular injury in the development of IRGN. A recent report identified anti-factor B autoantibodies as a contributing factor for complement AP activation in pediatric patients with PIGN. Moreover, C3G with glomerular NAPlr deposition without evidence of infection was reported. Taken together, the clinico-pathogenic features of IRGN overlap considerably with those of C3G. In this review, similarities and differences between the two diseases are highlighted.

Nephritis-Associated Plasmin Receptor (NAPlr): An Essential Inducer of C3-Dominant Glomerular Injury and a Potential Key Diagnostic Biomarker of Infection-Related Glomerulonephritis (IRGN)

Nephritis-associated plasmin receptor (NAPlr) was originally isolated from the cytoplasmic fraction of group A Streptococci, and was found to be the same molecule as streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and plasmin receptor (Plr) on the basis of nucleotide and amino acid sequence homology. Its main functions include GAPDH activity, plasmin-binding capacity, and direct activation of the complement alternative pathway (A-P). Plasmin trapped by deposited NAPlr triggers the degradation of extracellular matrix proteins, such as glomerular basement membranes and mesangial matrix, and the accumulation of macrophages and neutrophils, leading to the induction of plasmin-related endocapillary glomerular inflammation. Deposited NAPlr at glomerular endocapillary site directly activates the complement A-P, and the endocapillary release of complement-related anaphylatoxins, C3a and C5a, amplify the in situ endocapillary glomerular inflammation. Subsequently, circulating and in situ-formed immune complexes participate in the glomerular injury resulting in NAPlr-mediated glomerulonephritis. The disease framework of infection-related glomerulonephritis (IRGN) has been further expanded. GAPDH of various bacteria other than Streptococci have been found to react with anti-NAPlr antibodies and to possess plasmin-binding activities, allowing glomerular NAPlr and plasmin activity to be utilized as key biomarkers of IRGN.

Use of Immunosuppressive Therapy in the Treatment of IgA-dominant Infection-related Glomerulonephritis

A 51-year-old Japanese man who experienced colon cancer recurrence following primary and metastatic lesion resection was hospitalized due to facial cellulitis with febrile neutropenia and purpura on his lower extremities after chemotherapy. It was complicated by rapidly progressive glomerulonephritis. He was diagnosed with immunoglobulin A (IgA)-dominant endocapillary proliferative glomerulonephritis based on kidney histology. His glomeruli were positive for the nephritis-associated plasmin receptor, plasmin activity and galactose-deficient IgA1 (Gd-IgA1). A skin biopsy immunofluorescence study revealed IgA deposition within perivascular regions but no Gd-IgA1 deposition. The final diagnosis was IgA-dominant infection-related glomerulonephritis (IRGN). The patient's renal function returned to normal after receiving immunosuppressive therapy that consisted of a glucocorticoid and a cyclophosphamide. Immunosuppressive therapy should be considered in cases of IRGN if the patient's infection is completely under control.

The influences of α-hemolytic Streptococcus on class switching and complement activation of human tonsillar cells in IgA nephropathy

While β-hemolytic streptococcus (β-HS) infections are known to predispose patients to acute poststreptococcal glomerulonephritis, there is evidence that implicates α-hemolytic streptococcus (α-HS) in IgA nephropathy (IgAN). The alternative pathway of the complement system has also been implicated in IgAN. We aimed to explore the association between α-HS and complement activation in human tonsillar mononuclear cells (TMCs) in IgAN. In our study, α-HS induced higher IgA levels than IgG levels, while β-HS increased higher IgG levels than IgA levels with more activation-induced cytidine deaminase, in TMCs in the IgAN group. Aberrant IgA1 O-glycosylation levels were higher in IgAN patients with α-HS. C3 and C3b expression was decreased in IgAN patients, but in chronic tonsillitis control patients, the expression decreased only after stimulation with β-HS. Complement factor B and H (CFH) mRNA increased, but the CFH concentration in culture supernatants decreased with α-HS. The percentage of CD19 + CD35 + cells/complement receptor 1 (CR1) decreased with α-HS more than with β-HS, while CD19 + CD21 + cells/complement receptor 2 (CR2) increased more with β-HS than with α-HS. The component nephritis-associated plasmin receptor (NAPlr) of α-HS was not detected on tonsillar or kidney tissues in IgAN patients and was positive on cultured TMCs and mesangial cells. We concluded that α-HS induced the secretion of aberrantly O-glycosylated IgA while decreasing the levels of the inhibitory factor CFH in culture supernatants and CR1 + B cells. These findings provide testable mechanisms that relate α-HS infection to abnormal mucosal responses involving the alternative complement pathway in IgAN.

Nephritis-associated plasmin receptor (NAPlr)-positive glomerulonephritis in a case of ANCA-negative small vessel vasculitis

A 75-year-old man with fever was diagnosed with alveolar hemorrhage. Antineutrophil cytoplasmic antibodies for myeloperoxidase and proteinase 3 were absent. He received corticosteroid therapy, which immediately improved his symptoms and chest radiological findings. After the discontinuation of corticosteroids, fever and general fatigue relapsed, and renal function deteriorated with hematuria and proteinuria. A nerve conduction study revealed mononeuritis multiplex. Renal biopsy demonstrated focal necrotizing crescentic glomerulonephritis with endocapillary proliferative lesions, immunofluorescence C3 deposits, and electron-microscopic subepithelial hump-like deposits. Nephritis-associated plasmin receptor (NAPlr) and plasmin activity, biomarkers of infection-related glomerulonephritis, were positive in glomeruli. Although pathological findings suggested infection-related glomerulonephritis (IRGN), clinical manifestations, such as alveolar hemorrhage and mononeuritis multiplex, suggested systemic small vessel vasculitis. After corticosteroid therapy, systemic symptoms disappeared, and the gradual amelioration of hematuria and proteinuria was observed. Based on the clinical symptoms for which steroid therapy was effective, the patient was considered to have systemic small vessel vasculitis, the etiology of which may have been associated with infection.

Galactose-deficient IgA1 and nephritis-associated plasmin receptors as markers for IgA-dominant infection-related glomerulonephritis: A case report

RATIONAL

Immunoglobulin A (IgA) nephropathy is a common heterogeneous kidney disease. One of the causes of secondary immunoglobulin A nephropathy is infection-related glomerulonephritis (IRGN), however, its accurate diagnosis is difficult.

PATIENT CONCERNS

We report a rare case of an 82-year-old male presenting rapidly progressive glomerulonephritis. Assessment of a kidney biopsy by light microscopy revealed endocapillary glomerulonephritis with subendothelial deposits, such as wire loop lesions and cellular crescents. Immunofluorescence demonstrated strong staining for IgA and C3 along the glomerular capillary. Additional tests included positive staining for nephritis-associated plasmin receptor and positive plasmin activity in the glomeruli. Moreover, IgA and galactose-deficient IgA1 (Gd-IgA1) staining merged using immunofluorescence, followed by confirmation of high serum levels of Gd-IgA1 (9.3 μg/mL) by ELISA was observed.

DIAGNOSIS

The diagnosis of IgA-dominant IRGN was made.

INTERVENTIONS AND OUTCOMES

We have initiated treatment with intravenous methylprednisolone 500 mg/day for 3 days, followed by oral prednisolone 25 mg/d as rapidly progressive glomerulonephritis. However immunosuppressive therapy was halted because of a poor response, and hemodialysis was initiated.

LESSONS

This is a case of IgA-dominant IRGN patient exhibiting positive glomerular staining for nephritis-associated plasmin receptor accompanied with high titers of serum Gd-IgA1. Our observations suggest that serum and kidney tissue of Gd-IgA1 may be useful for the diagnosis of IgA-dominant IRGN.

Factors Affecting the Progression of Infection-Related Glomerulonephritis to Chronic Kidney Disease

Acute glomerulonephritis (AGN) triggered by infection is still one of the major causes of acute kidney injury. During the previous two decades, there has been a major paradigm shift in the epidemiology of AGN. The incidence of poststreptococcal acute glomerulonephritis (PSAGN), which develops after the cure of group A Streptococcus infection in children has decreased, whereas adult AGN cases have been increasing, and those associated with nonstreptococcal infections, particularly infections by Staphylococcus, are now as common as PSAGN. In adult AGN patients, particularly older patients with comorbidities, infections are usually ongoing at the time when glomerulonephritis is diagnosed; thus, the term “infection-related glomerulonephritis (IRGN)” has recently been popularly used instead of “post-infectious AGN”. The prognosis of children with PSAGN is generally considered excellent compared with that of adult IRGN cases. However, long-term epidemiological analysis demonstrated that an episode of PSAGN in childhood is a strong risk factor for chronic kidney disease (CKD), even after the complete remission of PSAGN. Although the precise mechanism of the transition from IRGN to CKD remains unknown, its clarification is important as it will lead to the prevention of CKD. In this review, we therefore focus on the possible factors that may contribute to the progression of IRGN into CKD. Four factors, namely, persistent infection, genetic background of the host’s complement system, tubulointerstitial changes, and pre-existing histological damage, are discussed.

Glomerular Deposition of Nephritis-Associated Plasmin Receptor (NAPlr) and Related Plasmin Activity: Key Diagnostic Biomarkers of Bacterial Infection-related Glomerulonephritis

It is widely known that glomerulonephritis (GN) often develops after the curing of an infection, a typical example of which is GN in children following streptococcal infections (poststreptococcal acute glomerulonephritis; PSAGN). On the other hand, the term “infection-related glomerulonephritis (IRGN)” has recently been proposed, because infections are usually ongoing at the time of GN onset in adult patients, particularly in older patients with comorbidities. However, there has been no specific diagnostic biomarker for IRGN, and diagnosis is based on the collection of several clinical and pathological findings and the exclusion of differential diagnoses. Nephritis-associated plasmin receptor (NAPlr) was originally isolated from the cytoplasmic fraction of group A streptococcus as a candidate nephritogenic protein for PSAGN and was found to be the same molecule as streptococcal glyceraldehyde-3-phosphate dehydrogenase and plasmin receptor. NAPlr deposition and related plasmin activity were observed with a similar distribution pattern in the glomeruli of patients with PSAGN. However, glomerular NAPlr deposition and plasmin activity could be observed not only in patients with PSAGN but also in patients with other glomerular diseases, in whom a preceding streptococcal infection was suggested. Furthermore, such glomerular staining patterns have been demonstrated in patients with IRGN induced by bacteria other than streptococci. This review discusses the recent advances in our understanding of the pathogenesis of bacterial IRGN, which is characterized by NAPlr and plasmin as key biomarkers.

Henoch-schonlein Purpura Nephritis with Renal Interstitial Lesions

Objective

To investigate the clinical pathology and prognosis & outcome of Henoch-Schonlein purpura nephritis (HSPN) with renal interstitial lesions.

Methods

All 148 patients were analyzed for clinical, renal pathological, and prognostic features. Patients with no, mild, and moderate- severe renal tubulo-interstitial lesions were included in group A, B and C, respectively.

Results

The estimated glomerular filtration rate (eGFR) of group B was significantly lower than that of group A. The levels of serum creatinine and blood urea nitrogen in group C were significantly higher than those in groups A and B. Clinical type II was correlated with pathological types II and IIIa; pathological type IV and IIIb were correlated with clinical type VI and IV. There were significant differences in the level of red blood cells in urinary sediment, levels of urine occult blood and in the prognosis among the 3 groups.

Conclusion

Clinically, Type II is the most common cause; pathologically, Type IIIa is more common. The severity of renal tubulo-interstitial lesions is positively correlated with a decline in renal function and GFR. There is a correlation between the severity of renal tubulo-interstitial lesions and the severity of hematuria. Most patients with HSPN have a good prognosis.

Streptococcal Infection-related Nephritis (SIRN) Manifesting Membranoproliferative Glomerulonephritis Type I

We herein report the case of an 18-year-old boy who developed nephrotic syndrome and hypertension after upper airway inflammation. Post-streptococcal acute glomerulonephritis was diagnosed on the basis of a high antistreptolysin O titer, hypocomplementemia, proteinuria, and microscopic hematuria. A renal biopsy was performed due to persistent proteinuria, and the pathological diagnosis was membranoproliferative glomerulonephritis (MPGN) type I. Glomeruli showed positive staining for nephritis-associated plasmin receptor (NAPlr), a nephritogenic group A streptococcal antigen, and plasmin activity was found in a similar distribution as NAPlr deposition. This rare case of streptococcal infection-related nephritis (SIRN) manifesting MPGN type I supports the histological diversity of SIRN.

The role of nephritis-associated plasmin receptor (NAPlr) in glomerulonephritis associated with streptococcal infection

It is well known that glomerulonephritis can occur after streptococcal infection, which is classically referred to as acute poststreptococcal glomerulonephritis (APSGN). The pathogenic mechanism of APSGN has been described by so-called immune complex theory, which involves glomerular deposition of nephritogenic streptococcal antigen and subsequent formation of immune complexes in situ and/or the deposition of circulating antigen-antibody complexes. However, the exact entity of the causative antigen has remained a matter of debate. We isolated a nephritogenic antigen for APSGN from the cytoplasmic fractions of group A streptococcus (GAS) depending on the affinity for IgG of APSGN patients. The amino acid and the nucleotide sequences of the isolated protein revealed to be highly identical to those of reported plasmin(ogen) receptor of GAS. Thus, we termed this antigen nephritis-associated plasmin receptor (NAPlr). Immunofluorescence staining of the renal biopsy tissues with anti-NAPlr antibody revealed glomerular NAPlr deposition in essentially all patients with early-phase APSGN. Furthermore, glomerular plasmin activity was detected by in situ zymography in the distribution almost identical to NAPlr deposition in renal biopsy tissues of APSGN patients. These data suggest that NAPlr has a direct, nonimmunologic function as a plasmin receptor and may contribute to the pathogenesis of APSGN by maintaining plasmin activity.

A case of idiopathic membranoproliferative glomerulonephritis with a transient glomerular deposition of nephritis-associated plasmin receptor antigen

The differential diagnosis of acute poststreptococcal glomerulonephritis (APSGN) and idiopathic membranoproliferative glomerulonephritis (MPGN) is sometimes difficult, as they share several key features in their laboratory and histological findings, especially during the acute phase of the diseases. We herein report an idiopathic case of MPGN in which the glomerular deposition of nephritis-associated plasmin receptor (NAPlr), a recently identified nephritic antigen for APSGN, was demonstrated. A 24-year-old postpartum woman developed nephrotic syndrome and hypocomplementemia. Although she showed no apparent findings of a prior infection, her serum titer of antistreptolysin O antibody was elevated. Renal biopsies were performed twice at intervals of 6 months, both of which showed findings fully consistent with those of MPGN. Of note, fluorescent immunostaining for NAPlr was positive in the glomeruli of the first biopsy but not in the second. Despite the use of a corticosteroid, hypocomplementemia persisted for more than 1 year. It was therefore suggested that a streptococcal infection may have influenced the development of glomerular injury in this idiopathic case of MPGN.

Periodic fever syndrome with relapsing glomerulonephritis: a case report and teaching points

We report a case of relapsing mesangial and endocapillary proliferative glomerulonephritis (GN) associated with a periodic fever syndrome. The patient presented 11 times in >4 years with acute febrile episode followed in 1–3 days by hematuria, thrombocytopenia and other symptoms of acute GN with variable severity of acute kidney injury. In three episodes, the patient required renal replacement therapy for 7, 10 and 2 treatments, respectively. Shortly after the acute symptoms of the febrile episode had resolved each time, the kidney function would recover and the serum creatinine would return to baseline. Two kidney biopsies obtained during separate episodes showed acute tubular injury along with morphological changes resembling post-infectious GN but with no clinical evidence to support an infectious etiology. Multiple treatment regimens were unable to control the disease. Symptoms were alleviated by rituximab but did not completely remit. Stable remission of the periodic fever and GN was finally achieved after anakinra therapy was initiated 18 months ago. Since then, the patient had several episodes of documented infection without high fever and nephritic kidney manifestations. His kidney function remained stable with normal serum creatinine.

Clinical and histologic resolution of poststreptococcal glomerulonephritis with large subendothelial deposits and kidney failure

A 16-year-old male adolescent who had fallen and scratched his knee developed cold-like symptoms. Gross hematuria, oliguria, and peripheral edema appeared about 2 weeks after his fall. Tests showed hypocomplementemia, increased antistreptolysin O titers, and severe kidney failure with hematuria/proteinuria. Kidney biopsy showed endocapillary proliferative glomerulonephritis visible using light microscopy and deposits of complement C3 on capillary walls, detectable using immunofluorescence microscopy. Although these findings suggested that he had acute poststreptococcal glomerulonephritis (APSGN), electron microscopy failed to detect subepithelial humps, a feature typical of APSGN; instead, massive electron-dense deposits were visible in the subendothelial space. A second biopsy performed 3 months later showed mesangial cell proliferation without endocapillary proliferation using light microscopy and the disappearance of subendothelial electron-dense deposits in electron micrographs, suggesting that APSGN had resolved. Glomerular deposition of nephritis-associated plasmin receptor, a nephritogenic streptococcal antigen, was observed in the first biopsy specimen, but not the second. The patient required 4 hemodialysis treatments, and within 1 year of supportive therapy only, kidney function and urinalysis had normalized. This is an interesting case of APSGN presenting with acute kidney injury and atypical massive subendothelial deposits, but no subepithelial deposits on electron microscopy, a pattern resembling that in membranoproliferative glomerulonephritis type I.

Clinical remission of Henoch-Schönlein purpura nephritis after a monotherapeutic tonsillectomy

We herein describe an adult male patient who presented with tonsillitis, purpura, hematuria, and proteinuria. The serological analyses revealed elevated serum antistreptolysin, and the throat culture yielded Lancefield group A β-hemolytic streptococci. A renal biopsy revealed mild mesangial proliferation associated with granular mesangial depositions of IgA and C3, consistent with Henoch-Schönlein purpura nephritis (HSPN). Initially, the patient was treated with dipyridamole, which was followed by limited improvements in the proteinuria and hematuria. Nine months later, the tonsillitis relapsed due to GAS infection and deteriorated urinary abnormalities were noticed, which finally disappeared after monotherapeutic tonsillectomy. Although the impact of tonsillectomy on the treatment of HSPN remains to be characterized, our observations suggest that tonsillectomy in the present patient played a pivotal role in facilitating the recovery of the renal injuries. Because the arbitrary application of a tonsillectomy appears to be accompanied by ethical concerns, the evaluation of the clinical benefits of this procedure should be addressed more directly in the future.

Henoch-Schönlein nephritis associated with streptococcal infection and persistent hypocomplementemia: a case report

Introduction

Henoch-Schönlein purpura is a systemic disease with frequent renal involvement, characterized by IgA mesangial deposits. Streptococcal infection can induce an abnormal IgA immune response like Henoch-Schönlein purpura, quite similar to typical acute post-infectious glomerulonephritis. Indeed, hypocomplementemia that is typical of acute glomerulonephritis has also been described in Henoch-Schönlein purpura.

Case presentation

We describe a 14-year-old Caucasian Spanish girl who developed urinary abnormalities and cutaneous purpura after streptococcal infection. Renal biopsy showed typical findings from Henoch-Schönlein purpura nephritis. In addition, she had low serum levels of complement (C4 fraction) that persisted during follow-up, in spite of her clinical evolution. She responded to treatment with enalapril and steroids.

Conclusion

The case described has, at least, three points of interest in Henoch-Schönlein purpura: 1) Initial presentation was preceded by streptococcal infection; 2) There was a persistence of low serum levels of complement; and 3) There was response to steroids and angiotensin-converting enzyme inhibitor in the presence of nephrotic syndrome. There are not many cases described in the literature with these characteristics. We conclude that Henoch-Schönlein purpura could appear after streptococcal infection in patients with abnormal complement levels, and that steroids and angiotensin-converting enzyme inhibitor could be successful treatment for the disease.

Tissue deposits of IgA-binding streptococcal M proteins in IgA nephropathy and Henoch-Schonlein purpura

IgA nephropathy (IgAN) and Henoch-Schönlein purpura (HSP) are diseases characterized by IgA deposits in the kidney and/or skin. Both may arise after upper respiratory tract infections, but the pathogenic mechanisms governing these diseases remain unclear. Patients with IgAN (n = 16) and HSP (n = 17) were included in this study aimed at examining whether IgA-binding M proteins of group A streptococci could be involved. As M proteins vary in sequence, the study focused on the IgA-binding-region (IgA-BR) of three different M proteins: M4, M22, and M60. Renal tissue from IgAN and HSP patients and skin from HSP patients were examined for deposits of streptococcal IgA-BR by immunohistochemistry and electron microscopy using specific antibodies, and a skin sample from a HSP patient was examined by mass spectrometry. IgA-BR deposits were detected in 10/16 IgAN kidneys and 7/13 HSP kidneys. Electron microscopy demonstrated deposits of IgA-BRs in the mesangial matrix and glomerular basement membrane, which colocalized with IgA. Skin samples exhibited IgA-BR deposits in 4/5 biopsies, a result confirmed by mass spectrometry in one patient. IgA-BR deposits were not detected in normal kidney and skin samples. Taken together, these results demonstrate IgA-BR from streptococcal M proteins in patient tissues. IgA-BR, would on gaining access to the circulation, encounter circulatory IgA and form a complex with IgA-Fc that could deposit in tissues and contribute to the pathogenesis of IgAN and HSP.

Gallbladder wall thickening in a patient with acute poststrepotcoccal glomerulonephritis

Although thickening of the gallbladder wall is a relatively frequent finding on diagnostic imaging studies, the condition has never been reported in patients with acute poststreptococcal glomerulonephritis (APSGN). We describe a patient with APSGN who presented with transient thickening of the gallbladder wall. While the precise pathogenic mechanism underlying this change in our patient was unclear, elevated systemic venous pressure or subclinical vasculitis may have caused edema of the gallbladder wall.

Streptococcal zymogen type B induces angiotensin II in mesangial cells and leukocytes

Previous reports have shown that angiotensin II and oxidative stress may be important features in acute poststreptococcal glomerulonephritis (APSGN) and that streptococcal erythrogenic toxin type B (ETB) and its precursor (ETBP) may have an important role in the pathogenesis of APSGN. The aim of this study was to determine the effect of ETBP on the production of angiotensin II and oxidative stress in rat mesangial cells and human mononuclear leukocytes. Mesangial cells and leukocytes were isolated from digested glomeruli and by histopaque gradient, respectively, while ETBP was isolated from nephritogenic streptococcus cultures using a cation exchange column. Angiotensin II was determined by an enzyme-linked immunosorbent assay and by cytometrics. Superoxide anion, reduced glutathione, nitrites, lipid peroxidation and catalase activity were determined by cytochemical, biochemical and enzymatic assays. Inducible nitric oxide synthase expression was determined by cytometrics. An increased production of angiotensin II was observed in ETBP-treated mesangial cell and leukocyte cultures. The ETBP induced an elevated production of superoxide anions and nitrites in mesangial cells and superoxide anions in leukocytes, while this streptococcal protein decreased the expression of inducible nitric oxide synthase in leukocytes. The ETBP was capable of inducing an increased production of angiotensin II and increased oxidative stress, both of which may be important mediators of inflammatory events in the renal tissue and during APSGN.