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     

Incidence of circulating immune complexes in patients with acute poststreptococcal glomerulonephritis and in patients with streptococcal impetigo

In an attempt to further study the possible contribution of circulating immune complexes (CIC) in the pathogenesis of acute poststreptococcal glomerulonephritis, 61 patients with APSGN were studied during the first three weeks of the disease, and 13 patients with noncomplicated streptococcal impetigo as a control group. C1q solid phase ELISA and Conglutinin (K) solid phase ELISA were used to measure the levels of immune complexes. The incidence of CIC in a single serum sample from patients with APSGN was 48%. Elevated levels of immune complexes were found in 46% of the patients with streptococcal impetigo. The absolute levels of CIC were comparable in both groups of patients. No correlation was found among the presence of CIC and the clinical, immunoserological or pathological findings of the disease. Our results do not support the hypothesis that trapping of the circulating immune complexes play an important role on the renal injury poststreptococcal infection. Instead, we suggest that CIC are an epiphenomena present in APSGN, and may represent rather a systemic inflammatory immune response in patients with group A streptococcal infection.     

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.     

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.     

Erythrogenic toxin type B and its precursor isolated from nephritogenic streptococci induce leukocyte infiltration in normal rat kidneys.

BACKGROUND: Leukocyte infiltration is a common feature in renal biopsies from patients with acute poststreptococcal glomerulonephritis (APSGN). Cationic streptococcal erythrogenic toxin type B (ETB) and its precursor (ETBP) have been implicated in the pathogenesis of the disease, and the presence of ETB has been evidenced in renal biopsies from patients with APSGN. The present studies were performed to determine the effect of the ETBP and ETB on renal leukocyte infiltration and the mechanism(s) implicated in the phenomenon. METHODS: Male Sprague-Dawley rats were injected intrarenally with 100 microg of ETB or ETBP. Animals were sacrificed at 1, 6 and 24 h after injection and renal samples were studied by indirect immunofluorescence for the presence of leukocyte common antigen (LCA+) cells, C3, monocyte chemotactic protein-1 (MCP-1) and intercellular adhesion molecule-(ICAM-1), and by direct immunofluorescence for the presence of immunoglobulins. ETB and ETBP were tested for chemotactic effect and migration inhibition factor (MIF) activity by chemotaxis under agarose and agarose microdroplet methods, respectively. Streptococcal proteins were also tested for the capacity to induce MIF activity in rat glomerular cultures. To test for the influence of cationic charge on renal LCA+ cell infiltration, rats were injected with cationized ferritin or polyethyleneimine (PEI) and sacrificed 1 h later. RESULTS: An increased number of LCA+ cells was found in glomeruli and interstitial areas in ETB- or ETBP-injected animals. ETB and ETBP showed chemotactic and MIF activity on neutrophils and macrophages, and ETBP induced MIF activity in supernatants of glomerular cultures. Data obtained from C3, MCP-1, ICAM-1 or immunoglobulin renal staining in experimental animals were not significantly different when compared to control values. Cationized compounds failed to induce LCA+ cell infiltration; however, an increased number of glomerular LCA+ cells was observed after PEI perfusion. CONCLUSIONS: ETB and ETBP induce renal LCA+ cell infiltration during a short period after intrarenal injection, and this finding could be mediated by chemotactic and MIF activities. These observations could be relevant in the early events of pathogenesis of APSGN.     

Monoclonal antibody analysis of glomerular, tubulo-interstitial infiltrating immune cells in various glomerulonephritis

To investigate the role of cell-mediated immunity (CMI) in glomerulonephritis (GN), we identified the infiltrating immune cells both within the glomerulus and in the interstitium. Frozen sections from 103 patients with various forms of GN: 10 with minor glomerular abnormality (MGA) as control, 10 with minimal change nephrotic syndrome (MCNS), 10 with membranous nephropathy (MN), 9 with focal glomerulosclerosis (FGS), 30 with IgA nephropathy (IgAN), 22 with acute post streptococcal glomerulonephritis (APSGN), and 2 with rapidly progressive glomerulonephritis (RPGN) were examined using monoclonal antibodies (MoAb) by indirect immunoalkaline-phosphatase labelling. In most glomerulonephritis, monocyte/M phi and helper/inducer T cells were predominantly infiltrating in the interstitium, but intraglomerular infiltration was rare, except for APSGN. This interstitial infiltration increased proportionally to the level of serum creatinine, and was most prominent in RPGN. Apparently different distribution was seen in APSGN, that is, prominent increase in total number of intra-glomerular monocyte/M phi infiltration with slightly increased T cells. The change was correlated with time after onset; namely the more leucocytic infiltration was observed when the tissue was taken earlier. These data suggest that in APSGN, monocyte/M phi accumulate in glomeruli via cell mediated immunity in addition to humoral immune mechanism resulting in glomerular hypercellularity, whereas in most chronic glomerulonephritis interstitial leucocyte infiltration, particularly helper T cells and monocyte/M phi may play an important role in the progression of glomerulonephritis.     

Streptococcal exotoxin B increases interleukin-6, tumor necrosis factor alpha,interleukin-8 and transforming growth factor beta-1 in leukocytes

Previous reports have shown the presence of streptococcal erythrogenic exotoxin type B (ETB), leukocyte infiltration, interleukin-8 (IL-8), transforming growth factor-beta (TGF-β) and glomerular proliferation in renal biopsies from patients with acute post-streptococcal glomerulonephritis (APSGN). In addition, increased levels of plasma interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFα), and urinary IL-6, have also been reported in this disease. To determine the effect of streptococcal proteins on leukocyte proliferation and leukocyte production of IL-6, TNFα, IL-8 and TGF-β1, we cultured human mononuclear leukocytes with ETB or ETB precursor (ETBP). After 24 h, 48 h and 96 h, culture supernatants were assessed for cytokines by enzyme-linked immunosorbent assay (ELISA), and for leukocyte proliferation by a monoclonal antibody anti-proliferating cellular nuclear antigen (PCNA). A significant increase in all cytokines was found in ETB- or ETBP-treated cultures when compared with controls. A polyclonal anti-ETB antibody diminished the cytokine stimulatory effect of ETB. An increased number of PCNA-positive cells was observed in ETB or ETBP treated cultures at 48 h and 96 h. Cytokine production and proliferation were not correlated. The stimulatory effect of streptococcal exotoxin B on leukocyte cytokine production may be relevant in renal tissue 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.     

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.     

Monoclonal antibody analysis of glomerular hypercellularity in human glomerulonephritis

To determine the contribution of infiltrating circulating leucocytes to glomerular hypercellularity, and to further investigate the immune and inflammatory mechanisms involved in human glomerulonephritis, a series of renal biopsies were evaluated using cell-specific monoclonal antibodies. In ninety-three renal biopsies from patients with glomerulonephritis, intraglomerular leucocytes were identified by immunoperoxidase localization of monoclonal antibodies to the leucocyte-common antigen, and antigens characteristic of T-cell and T-cell subsets, B-cells, monocytes and granulocytes. Normal glomeruli contained a mean of 2 leucocytes, predominantly monocytes, per glomerular cross-section. No significant increase in leucocytes was found in 41 biopsies with non-proliferative types of glomerulonephritis. However, in renal biopsies from 22 of the 46 patients with proliferative forms of glomerulonephritis, there was a significant increase in glomerular leucocytes. These biopsies were from 5 patients with post-infectious glomerulonephritis (mean of 30 leucocytes per glomerulus), 11 patients with crescentic glomerulonephritis (mean of 16 leucocytes per glomerulus) and 6 patients with mesangial proliferative glomerulonephritis due to systemic lupus erythematosus (mean of 5 leucocytes per glomerulus). The increased intraglomerular leucocytes consisted of macrophages and granulocytes. T and B-cells were generally not found within glomeruli. Thus, glomerular hypercellularity in proliferative glomerulonephritis is in part due to infiltration by inflammatory cells. No evidence was found to directly incriminate cellular immune mechanisms in the pathogenesis of the glomerular lesions of glomerulonephritis since T-cells were not identified within glomeruli.     

Glomerular binding sites for peanut agglutinin in acute poststreptococcal glomerulonephritis

Streptococcal neuraminidase may be responsible for the development of auto-immune reactivity in acute poststreptococcal glomerulonephritis (APSGN). Neuraminidase may react with immunoglobulins in the circulation and with sialic acid-rich sites in the endothelial and epithelial glomerular capillary, therefore, extrinsic or intrinsic sialic acid-depleted substrate may be localized in the glomeruli. We studied renal biopsies from 17 patients with APSGN, 48 patients with other renal pathologies and 2 normal kidneys for the capacity to bind fluorescein-labelled peanut agglutinin (PNA) lectin. PNA has specificity for galactosyl radicals which are exposed after sialic acid removal. We similarly studied the kidneys of rats at intervals ranging from hours to 32 days after an intravenous injection of 0.02 units of neuraminidase per g of body weight. Five biopsies of APSGN patients and 2 biopsies from patients with renal pathologies different from APSGN showed glomerular PNA binding. Of APSGN patients, 4 corresponded to the 5 patients biopsied within 30 days of the beginning of the disease and only 1 biopsy was positive in the 12 patients who were biopsied later. The PNA binding predominated in the mesangium and the pattern was irregular and speckled. These findings suggest that sialic-acid depleted material is present in the glomeruli, early in the course of APSGN.     

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.     

Glomerular plasmin-like activity in relation to nephritis-associated plasmin receptor in acute poststreptococcal glomerulonephritis

A nephritogenic antigen for acute poststreptococcal glomerulonephritis (APSGN) was isolated recently from group A streptococcus and termed nephritis-associated plasmin receptor (NAPlr). In vitro experimental data indicate that the pathogenic role of NAPlr occurs through its ability to bind to plasmin and maintain its proteolytic activity. However, the mechanism whereby this antigen induces glomerular damage in vivo has not been fully elucidated. Renal biopsy tissues from 17 patients with APSGN, 8 patients with rapidly progressive glomerulonephritis, and 10 normal kidneys were analyzed in this study. Plasmin-like activity was assessed on cryostat sections by in situ zymography with a plasmin-sensitive synthetic substrate. Serial sections were simultaneously assessed for NAPlr deposition by immunofluorescence staining. Glomerular plasmin-like activity was absent or weak in normal controls and in patients with rapidly progressive glomerulonephritis, although tubulointerstitial activity was occasionally detected. Prominent glomerular plasmin-like activity was found in patients who had APSGN and in whom glomerular NAPlr was positive, whereas it was absent or weak in patients who had APSGN and in whom glomerular NAPlr was negative. The distribution of glomerular plasmin-like activity was identical to that of NAPlr deposition but was generally different from that of fibrin(ogen) deposition as assessed by double staining. The activity was abolished by the addition of aprotinin to the reaction mixture but was not altered by the addition of a matrix metalloprotease inhibitor, a cysteine protease inhibitor, or inhibitors of plasminogen activators. Thus, upregulated glomerular plasmin-like activity in relation to NAPlr deposition in APSGN was identified. This result supports the nephritogenic character of NAPlr and offers insight into the mechanism whereby this antigen induces nephritis.     

Celiac disease associated with immune complex glomerulonephritis.

A patient with immune complex glomerulonephritis and celiac disease without dermatitis herpetiformis or other underlying disease associated with glomerulonephritis is presented. Antibodies to wheat proteins were found in serum and withdrawal of gluten from the diet resulted in disappearance of immune complexes from serum and resolution of both renal and intestinal disease, suggesting a dietary source of antigen. Despite extensive immunopathologic studies of the renal biopsy, neither dietary nor endogenous brush border antigens were demonstrated in glomeruli.     

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.     

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.     

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.     

Increased production of chemotactic cytokines and elevated proliferation and expression of intercellular adhesion molecule-1 in rat mesangial cells treated with erythrogenic toxin type B and its precursor isolated from nephritogenic streptococci.

BACKGROUND: Previous reports have demonstrated the presence of streptococcal erythrogenic toxin type B (ETB) as well as proliferation and expression of adhesion molecules along with leukocyte infiltrations in biopsies from patients with acute post-streptococcal glomerulonephritis (APSGN). The purpose of the present study was to correlate infiltrative and proliferative events with interactions between ETB or its precursor (ETBP) and intrinsic mesangial cells. METHODS: Rat mesangial cells were cultured with ETB or ETBP (50 micro g/ml) while measuring production of monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-2 (MIP-2) and while examining proliferation and expression of intercellular adhesion molecule-1 (ICAM-1). After 24, 48 and 96 h of incubation, MCP-1 and MIP-2 in culture supernatants were assessed by enzyme-linked immunosorbent assay (ELISA). Cells were assessed for proliferation by incorporation of radioactive thymidine and expression of ICAM-1 was measured by indirect immunofluorescence and by cellular ELISA. RESULTS: Compared with controls, treatment with either ETBP or ETB significantly increased MCP-1 and MIP-2 levels in mesangial cell cultures. Mesangial cells also showed elevated proliferation at 96 h of culture when treated with streptococcal proteins. Although production of MCP-1 and MIP-2 was not correlated with proliferation, treatment with ETBP resulted in a significant correlation between MCP-1 production and proliferation. Immunofluorescence studies revealed an increased expression of ICAM-1 in ETBP/ETB-treated mesangial cells. In addition, cellular ELISA studies showed increased absorbance in cultures treated with ETBP/ETB. Finally, low serum concentrations in the culture medium potentiated the stimulatory effect of ETB on MCP-1 production. CONCLUSIONS: Our findings, by demonstrating a role for cationic streptococcal ETB or ETBP in the induction of chemotactic molecules as well as the proliferation and expression of adhesion molecules, delineate an additional possible pathway for the pathogenesis of APSGN.     

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.