Decrease in mean platelet survival time in acute poststreptococcal glomerulonephritis (APSGN)

In an attempt to study further the possible participation of platelets in the pathogenesis of acute poststreptococcal glomerulonephritis (APSGN), we studied the platelet survival time, as an index of platelet activation, in 22 patients with APSGN. Mean platelet survival time was computed from the disappearance of radioactivity from blood, sampled serially after injection of autologous 51Cr-labelled platelets. C1q solid phase ELISA and conglutinin (K) solid phase ELISA were used to measure the serum levels of immune complexes. The platelet survival time in APSGN patients was 113 +/- 10 h vs 197 +/- 10 h in the control group (p less than 0.001); 68% of the patients had a shortened platelet survival, lower than 95% confidence limit. There was a significant increase in the platelet survival in the six patients that were studied after recovery from acute nephritic syndrome. There was no significant association between the mean platelet times survival and CICs (circulating immune complexes). Similarly, no significant correlation was found between the mean platelet lifespan and the severity of the glomerular disease, as assessed by the serum creatinine level and the proteinuria. These results support evidence of platelet activation and consumption in APSGN and we suggest that this activation occurs in the glomeruli capillary wall, due to platelet-vascular wall interaction.     

Detection of IgG-rheumatoid factor in sera of patients with acute poststreptococcal glomerulonephritis and its relationship with circulating immunecomplexes

Rheumatoid factors (RF) were measured in sera from 75 patients with acute poststreptococcal glomerulonephritis (APSGN) and compared with normal controls, patients with rheumatoid arthritis in activity and acute rheumatic fever. Using two sensitive and specific solid phase radioimmunoassays, IgM-RF and IgG-RF were detected, respectively, in 15% and 32% of the patients with APSGN. A positive correlation (r = 0.37, n = 75, p less than 0.05) was obtained between serum levels of IgG-RF and circulating immune complexes determined by conglutinin assay. Chromatographic studies in serum from two patients with APSGN demonstrated that the circulating IgG-RFs were mainly free, not complexed. It is suggested that RFs, particularly of the IgG class, may participate in the pathogenesis of the renal injury in some patients with APSGN.     

Presence of circulating immune complexes in the classic form of hemolytic uremic syndrome: a constant finding

In an attempt to further study the possible contribution of circulating immune complexes (CIC) in the pathogenesis of the classic form of hemolytic uremic syndrome, 9 patients were studied during the acute phase of the diseases. C1q solid-phase ELISA and conglutinin solid-phase ELISA, were used to measure the levels of immune complexes. All 9 were positive in one or both assays. No correlation was found between the levels of CIC and the clinical severity of the disease. The constant finding of positive CIC in these patients might represent an epiphenomenon, point out the postinfectious nature of this disease but also suggest a possible pathogenic role.     

Humoral immunity to streptococcal antigen in acute and chronic glomerulonephritis

A study was carried out to verify the clinical usefulness of the elaborated method for the measurement of antistreptococcal antibody in revealing the streptococcal etiology of glomerulonephritis.In 158 patients with glomerulonephritis antistreptococcal antibody (ASA), circulating immune complexes (CIC) and haemolytic activity of the complement were measured.On the basis of immune complex formation it has been concluded that streptococcal infection may cause glomerulonephritis. Serial determinations of ASA and CIC are helpful in establishing the streptococcal etiology of glomerulonephritis and in monitoring the course of the disease.     

Cationic antigens in poststreptococcal glomerulonephritis

Antigen charge is an important factor in the pathogenesis of experimental immune complex glomerulonephritis. Its potential role in man was investigated in post-streptococcal glomerulonephritis, a disease where the causative agent is known. Cationic, extracellular streptococcal antigens were detected in 8 of 18 renal biopsies from patients with acute poststreptococcal glomerulonephritis (APSGN). The antigen was found mainly in earlier biopsies in which both IgG and IgM were present. Patients' sera taken at the time of biopsy contained antibody to cationic, streptococcal antigens. Cationic moieties are known to have affinity for the glomerular basement membrane and it is possible that the type of antigen described here initiates APSGN via in situ immune complex formation.     

Failure to detect unique reactivity to streptococcal streptokinase in either the sera or renal biopsy specimens of patients with acute poststreptococcal glomerulonephritis.

Using purified group A streptokinase (SKA) as the antigen, ELISA assays were carried out on the sera of normal unaffected children, acute poststreptococcal glomerulonephritis patients (APSGN) and acute rheumatic fever patients (ARF). The results demonstrate that antibody titers to SKA increase with age in normal children and by age 8 years the vast majority of children have antibodies to SKA. APSGN patients did not demonstrate unique reactivity to SKA when compared to ARF patients either at time of onset of disease or during convalescence. Polyclonal and monoclonal antibodies to SKA which recognize both group A and C streptokinase failed to detect the presence of streptokinase in the biopsy sections obtained from ten well-documented APSGN patients. We conclude that there is no unique reactivity to group A streptokinase in the sera of APSGN patients. Furthermore, we failed to demonstrate the presence of streptokinase in the biopsy specimens of an early case of APSGN patients.     

IgG, IgA and IgM rheumatoid factors in patients with glomerulonephritis

Rheumatoid factors (RF), autoantibodies to IgG, have been postulated to have some pathogenetic role in the development of some types of glomerulonephritis. A simple and sensitive solid-phase fluorescence immunoassay was employed to determine whether IgG, IgA and IgM RF were detectable in sera from patients with various types of glomerulonephritis, rheumatoid arthritis (RA) and those with various streptococcal infections. IgG, IgA and IgM RF were significantly increased in the majority of patients with RA, lupus nephritis (SLE), acute poststreptococcal glomerulonephritis (APSGN) and various streptococcal infections. The titers of IgG and IgA RF were significantly higher in patients with APSGN than in those with simple pharyngitis. IgM RF was increated in patients with IgA nephropathy (IgA-N) and in those with membranoproliferative glomerulonephritis type I (MPGN). No significantly high RF was observed in membranous nephropathy (MN) or chronic mesangial proliferative glomerulonephritis without IgA deposition (PGN). It is suggested that some autologous immune mechanisms may be involved in the pathogenesis of some types of glomerulonephritis.     

Age influence on mononuclear phagocyte system Fc-receptor function in poststreptococcal nephritis

The Fc-receptor function of the mononuclear phagocyte system (MPS) was examined in 41 children and adult patients, by measuring the clearance of IgG-sensitized, 51Cr-labeled erythrocytes. The Fc-receptor-mediated clearance observed in patients (mean +/- SE) was not significantly different as compared to the control group of similar age distribution. However, the immune clearance time was significantly age-correlated in both groups (acute poststreptococcal glomerulonephritis, APSGN, r = 0.39, p less than 0.05; control r = 0.63, p less than 0.01). The magnitude of the Fc-specific immune clearance and the serum creatinine were also significantly correlated (r = 0.59; p less than 0.01). Circulating immune complexes (as measured by the C1q and conglutinin ELISA) did not correlate with immune clearance, which remained stable in longitudinal studies. Age-related changes in MPS Fc-receptor function could explain, at least in part, prognostic differences between children and adult patients with APSGN.     

Nephritis-associated plasmin receptor and acute poststreptococcal glomerulonephritis: characterization of the antigen and associated immune response

The role of nephritis-associated antigen as a virulence factor for acute poststreptococcal glomerulonephritis (APSGN) remains to be fully clarified. Nephritis-associated plasmin receptor (NAPlr) was previously isolated from group A streptococcus (GAS) and shown to bind plasmin(ogen). The nucleotide sequence of the naplr gene from GAS isolates obtained from patients with APSGN was determined. The sequence of the putative open reading frame (1011 bp) showed 99.8% identity among isolated strains. Homology screen revealed an exact match with streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH). NAPlr exhibited GAPDH activity in zymography, and it activated the complement pathway in vitro. In APSGN kidney biopsy specimens, NAPlr was observed mainly in the early stage of the disease (1 to 14 d after onset) but was not colocalized with either C3 or IgG as assessed by double immunofluorescence staining. Sera of patients with APSGN, patients with GAS infection without renal involvement, nonrenal pediatric patients, and healthy adults as controls were assayed for anti-NAPlr antibody titers. Anti-NAPlr antibodies were present most frequently in APSGN sera, and antibody titers were also significantly higher than in patients with GAS infection alone or in other control patients. Moreover, antibody titers remained elevated during the entire 10-yr follow-up period.     

Sequence and expression of NAPlr is conserved among group A streptococci isolated from patients with acute poststreptococcal glomerulonephritis (APSGN) and non-APSGN

BACKGROUND: The relation of nephritis-associated plasmin receptor (NAPlr) as a nephritogenic antigen in group A streptococci (GAS), to acute poststreptococcal glomerulonephritis (APSGN) and the potential of specific strains to cause APSGN are not fully understood. It would be helpful to determine whether certain GAS strains from APSGN patients specifically express NAPlr and whether strains from non-APSGN patients express lower levels or an altered form of NAPlr. METHODS: The sequence and levels of expression of NAPlr were assayed for strains of GAS isolated from patients with APSGN, pharyngitis, scarlet fever or toxic shock-like syndrome. Findings were evaluated with respect to naplr gene sequence, expression level of NAPlr, serotype and disease type. RESULTS: In GAS strains from both APSGN and non-APSGN patients, the naplr gene showed few or no nucleotide alterations, and both types of GAS strains expressed NAPlr in vitro. There were no obvious differences in naplr gene sequence, expression of NAPlr, serotype or disease type between the GAS strains. In addition, groups C and G streptococci also carried a conserved naplr gene and expressed NAPlr in vitro. CONCLUSIONS: These groups of streptococci that express NAPlr should be associated with APSGN, and this association may be independent of serotype or disease type.     

急性链球菌感染后肾炎患儿脂氧素A4、白三烯B4及15-脂氧化酶的变化及其意义

目的 探讨急性链球菌感染后肾炎（APSGN）患儿血、尿脂氧素A4（LXA4）、白三烯B4（LTB4）和白细胞15-脂氧化酶（15-LO）水平变化的意义。 方法 分别在22例APSGN患儿发病≤3 d（急性期）、10～14 d（恢复早期）和6～8周（恢复晚期）留取标本，采用ELISA方法测定血、尿LXA4和LTB4。对8例患儿应用RT-PCR方法测定白细胞15-LO表达。体外趋化法测定白细胞LTB4和中性粒细胞趋化功能。对照组为健康体检儿童。 结果 患儿急性期的血、尿LXA4和白细胞15-LO表达升高，恢复早期进一步升高（均P < 0.01）；在恢复晚期有所降低，但仍高于健康儿童(均P < 0.01)。患儿急性期的血、尿LTB4高于健康儿童（P < 0.01），在恢复早期和恢复晚期逐渐降低，仍高于健康儿童（P < 0.01）。体外应用15-S-羟二十碳四烯酸（15-S-HETE）或LXA4可抑制患儿白细胞合成LTB4，抑制中性粒细胞趋化功能。 结论 患儿血、尿LXA4和白细胞15-LO表达在恢复早期与血、尿LTB4变化相反。15-S-HETE和LXA4通过抑制LTB4而发挥抗炎作用，促进APSGN疾病的恢复。     

Circulating immune complexes in patients following clinically curative resection of colorectal cancer.

Sixty-nine patients have been followed prospectively after curative resection of Dukes-Kirklin B-2 or C colorectal cancer. Serial plasma samples were studied in selected patients to determine changes in circulating immune complex concentrations (CIC) following primary tumor resection, and to compare serial plasma CIC and carcinoembryonic antigen (CEA) levels. CIC was determined in an average of seven serial samples per patient by inhibition of antibody-dependent cell-mediated cytotoxicity (ADCC). CEA assays were performed by the Hanson Z-gel method. Two distinct patterns of serial CIC have emerged. In seven patients with no known tumor recurrences, serial CEA levels and CIC oscillated regularly and were inversely related. In seven of eight patients whose tumors recurred, both CEA and CIC rose together. In three patients with elevated plasma CEA levels due to inflammatory bowel disease, serial Ag-Ab complex concentrations did not vary, nor did separated Ag or Ab fractions inhibit ADCC. These data suggest that, in patients following curative resection of colorectal cancer, serial changes in circulating immune complexes may discriminate between transient CEA elevations which occur despite no known tumor recurrence and tumor recurrence which is beyond the capacity of adequate host antitumor defense.     

Is the nephritogenic antigen in post-streptococcal glomerulonephritis pyrogenic exotoxin B (SPE B) or GAPDH?

BACKGROUND: Acute glomerulonephritis can follow infection by group A streptococci. An immune-complex pathogenesis is accepted, but the causative antigen(s) is still controversial. In recent years, 2 streptococcal antigens, the cationic cysteine proteinase exotoxin B (SPE B) and the plasmin receptor, a glyceraldehyde phosphate dehydrogenase (Plr, GAPDH) have attracted attention because: (1) they were localized in glomeruli in patients with acute post-streptococcal glomerulonephritis (APSGN); and (2) serum antibody to these antigens was associated with nephritogenic streptococcal infections. To date, putative nephritogens were always tested independently. Here, the relevance of SPE B and GAPDH was evaluated in the same renal biopsies and serum samples of well-defined APSGN patients. METHODS: Renal biopsies (17 patients) and serum samples (53 patients) with APSGN and appropriate controls were examined. Immunofluorescent staining of frozen sections was performed using specific antibodies to SPE B and GAPDH. Serum antibodies were investigated by both enzyme-linked immunosorbent assay (ELISA) and Western blot methodology. RESULTS: Glomerular deposits of SPE B were demonstrated in 12/17 APSGN biopsies, and 2 cases were borderline; circulating antibodies were found in all instances (53/53 patients). Glomerular deposition of GAPDH was detected in 1/17 biopsies, and 2 cases were borderline; circulating antibodies were found in 5/47 patients. In 31 control biopsies, only weak staining for each antigen was found in 2 cases. CONCLUSION: In this study, glomerular deposits of and antibody response to zymogen/SPE B are more consistently present in APSGN than deposits and antibody response to GAPDH. Zymogen/SPE B is likely to be the major antigen involved in the pathogenesis of most cases of APSGN.     

Recurrence of acute poststreptococcal glomerulonephritis

Recurrence of acute poststreptococcal glomerulonephritis (APSGN) is a rare phenomenon. We present an 8-year-old boy with a second episode of APSGN 12 months following a complete clinical recovery from his initial attack. Renal histology, obtained from renal biopsies of the patient during the second attack, showed diffuse endocapillary proliferation, granular deposition of C3, IgG, IgA, and fibrinogen along capillary walls, and subepithelial electron-dense deposits. A new streptococcal cytoplasmic antigen (nephritis-associated plasmin receptor protein, NAPlr), which was recently identified as the pathogenic antigen in APSGN, was detected in the glomeruli of an early kidney biopsy specimen from the patient during the second attack of APSGN, using fluorescein isothiocyanate-labeled rabbit anti-NAPlr. However, antibodies against NAPlr, examined by Western blotting, were not present in sera from the patient. These results suggest that recurrence of APSGN in some patients may be caused by an absence of a natural immune response to NAPlr. Received: 7 September 2000 / Revised: 12 February 2001 / Accepted: 13 February 2001     

Monocyte chemoattractant protein-1 and interleukin-8 levels in children with acute poststreptococcal glomerulonephritis

The infiltration of leukocytes into the glomeruli is a major factor in inflammatory glomerular damage in acute poststreptococcal glomerulonephritis (APSGN). Chemokines participate in leukocyte infiltration. The aim of the present study was to investigate the role of monocyte chemoattractant protein-1 (CCL2/MCP-1) and interleukin-8 (CXL8/IL-8) in APSGN with special emphasis on their role in the clinical course of renal disease. Twenty-one children with APSGN were studied. Serum and urinary CCL2/MCP-1 and CXL8/IL-8 levels were measured by ELISA. The relationships between urinary chemokines and the degree of proteinuria were investigated. Serum and urinary CCL2/MCP-1 levels were significantly higher in the acute phase than in the resolution phase and in controls ( P <0.05). Urinary CCL2/MCP-1 levels in the control group were significantly lower than in both the acute and resolution phases ( P =0.01 and P =0.001, respectively). In the acute phase, urinary CCL2/MCP-1 correlated with the extent of proteinuria ( r =0.58, P =0.006) but not with serum CCL2/MCP-1 levels ( r =0.21, P =0.36). Urinary and serum CXL8/IL-8 levels were significantly elevated in the acute phase compared with the resolution phase and controls ( P <0.05). A consistent increase in urinary CCL2/MCP-1 was found in the acute phase of patients with APSGN, and this correlates with the degree of proteinuria. Our results emphasize the important role of locally produced chemokines in immune-mediated glomerular injury.     

Anticardiolipin antibodies in acute poststreptococcal glomerulonephritis and streptococcal impetigo.

Anticardiolipin (aCL) antibodies have been described in diverse clinical situations, linked to the risk of thrombosis in different vascular locations. They have been rarely studied in renal diseases, and occasionally they have been associated with glomerular thrombosis. We analyzed the incidence of aCL (isotypes IgG, IgA, and IgM) in samples, taken during the acute phase of the disease, from 27 well-documented patients having acute poststreptococcal glomerulonephritis. Twelve cases were positive on IgG testing, 1 case on IgA testing only, and no one was positive on IgM testing. A serological follow-up was performed with a second sample taken about 7 months later, for the patients initially positive on IgG testing showing persistence in 9. Clinical variables during the acute phase and after a follow-up period of 25 (range 6-89) months were analyzed for possible associations with the presence of these antibodies, but non was significantly related. Renal histopathological investigation did not reveal particular findings in the aCL-positive patients, and glomerular thrombosis was not found in any case. In addition, serum samples from 12 streptococcal impetigo patients without renal involvement were analyzed, showing similar incidence (4 positive on IgG testing, 1 of them positive on IgM testing as well, and no one positive on IgA testing) and titers of aCL antibodies. We conclude that the presence of aCL antibodies in acute poststreptococcal glomerulonephritis may be a marginal immunological phenomenon unrelated to the glomerular disease, triggered by the streptococcal infection.     

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.     

Terminal complement complexes in acute poststreptococcal glomerulonephritis

Activation of the complement cascade occurs in most cases of acute poststreptococcal glomerulonephritis (APSGN) and results in the formation of the terminal complement complexes (TCC). To examine the possible role of TCC in the pathogenesis of glomerular injury in APSGN, we studied 30 patients with the clinical diagnosis of APSGN. All patients had an elevated plasma SC5b-9 concentration at the onset of clinical nephritis. Serial plasma concentrations showed an inverse linear relationship with time after onset of clinical disease (r=–0.59,P=0.0008), while plasma C3 concentrations showed a positive linear relationship (r=0.78,P=0.0001). Renal biopsies of 5 patients demonstrated co-localization of C5b-9, S-protein, and C3 deposition in a glomerular capillary loop and mesangial distribution. Urinary excretion of TCC in the acute phase of APSGN was not elevated and was not a useful marker of disease activity. These data suggest that in APSGN with terminal complement pathway activation the local generation of TCC may contribute to the pathogenesis of the disease.     

Increased IL-6 in supernatant of rat mesangial cell cultures treated with erythrogenic toxin type B and its precursor isolated from nephritogenic streptococci

BACKGROUND/AIMS: Previous reports have shown the presence of streptococcal erythrogenic toxin type B (ETB), IL-8, transforming growth factor-beta (TGF-beta) and glomerular proliferation in renal biopsies from patients with acute poststreptococcal glomerulonephritis (APSGN). In addition, increased levels of plasma IL-6 and tumor necrosis factor-alpha (TNFalpha) and urinary IL-6 have also been reported in this disease. To determine the effect of ETB in mesangial cell cytokine production and proliferation, the concentration of several cytokines (IL-6, IL-1beta, TNFalpha, IL-10, IL-4, RANTES), soluble TNF receptor I (STNFR-I), soluble TNF receptor II (STNFR-II) and proliferation were measured in rat mesangial cells cultures after treatment with ETB or its precursor (ETBP). METHODS: To analyze the levels of cytokines and production of soluble receptors as well as proliferation, rat mesangial cells were cultured with ETB or ETBP (50 microg/ml). After 24, 48 and 96 h of incubation, culture supernatants were assessed for cytokines and receptors by ELISA and for proliferation by incorporation of radioactive thymidine. RESULTS: A significant increase in IL-6 levels was found in mesangial cell cultures treated with either ETBP or ETB when compared with controls. Streptococcal proteins treated mesangial cells also showed elevated levels of proliferation at 96 h. Increased production of IL-6 was not correlated with proliferation. A polyclonal anti-ETB antibody abolished the IL-6 stimulatory effect of ETB on mesangial cells. ETB/ETBP failed to increase the levels of other cytokines and cytokine soluble receptors. CONCLUSION: Streptococcal ETB/ETBP is capable of inducing increased production of IL-6 and proliferation on mesangial cells. These findings could be relevant in a possible early interaction of streptococcal proteins with mesangial cells and during the course of APSGN.     

Pathogenesis of poststreptococcal glomerulonephritis a century after Clemens von Pirquet

Considerable insight has been gained into the etiopathogenesis of poststreptococcal glomerulonephritis since the landmark theoretical construct of Clemens von Pirquet postulated that disease-causing immune complexes were responsible for the nephritis that followed scarlet fever. Over the years, molecular mimicry between streptococcal products and renal components, autoimmune reactivity and several streptococcal antigens have been extensively studied. Recent investigations assign a critical role to both in situ formation and deposition of circulating immune complexes that would trigger a variety of effector mechanisms. Glomerular plasmin-binding activity of streptococcal glyceraldehyde-3-phosphate-dehydrogenase may play a role in nephritogenicity and streptococcal pyrogenic exotoxin B and its zymogen precursor may be the long-sought nephritogenic antigen.