title: Elevated IgG titer against the C region of streptococcal M protein and its immunodeterminants in patients with poststreptococcal acute glomerulonephritis.
abstract: OBJECTIVE
  To determine the immune responses to the streptococcal M protein in patients with poststreptococcal acute glomerulonephritis (PSAGN).
  
  
  METHODS
  The gene coding type 12 M protein of group A streptococcus (M12), a known PSAGN-associated serotype, was cloned and expressed in Escherichia coli to investigate the specific immune responses to the M12 protein in patients with PSAGN. Recombinant M proteins for the variable N-terminal half (AB region) and conserved C-terminal half (C region) were produced separately. IgG titers against each region were measured by enzyme-linked immunosorbent assay in patients with PSAGN (n = 51), uncomplicated streptococcal pharyngitis (n = 26), chronic glomerulonephritis (n = 10), and in healthy control subjects (n = 51). Immunodominant domains within the M protein in PSAGN were further investigated by use of overlapping synthetic peptides.
  
  
  RESULTS
  IgG titers against the C region, but not the AB region, were markedly higher in the PSAGN group than in other groups (p < 0.01), and these titers were maintained for at least several months after antistreptolysin O or antistreptokinase levels had returned to normal. Studies with overlapping synthetic peptides demonstrated that increased IgG reactivity was observed against the C repeat blocks.
  
  
  CONCLUSIONS
  IgG titers against the C region are significantly elevated in patients with PSAGN, and it may be a diagnostic marker for PSAGN.
authors.affiliation: Department of Pediatrics, Kouchi Red-Cross Hospital, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Mori
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.forename: N
authors.initials: N
authors.lastname: Kamikawaji
authors.forename: T
authors.initials: T
authors.lastname: Sasazuki
mesh_terms: D000208:Acute Disease; D000907:Antibodies, Bacterial / Q000032:analysis*; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D000954:Antigens, Surface / Q000235:genetics / Q000276:immunology*; D000989:Antistreptolysin / Q000032:analysis; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D015415:Biomarkers / Q000032:analysis; D002352:Carrier Proteins; D016022:Case-Control Studies; D002648:Child; D002908:Chronic Disease; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D015870:Gene Expression; D005921:Glomerulonephritis / Q000276:immunology / Q000382:microbiology*; D006801:Humans; D016056:Immunodominant Epitopes / Q000235:genetics / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis*; D008297:Male; D010455:Peptides; D010612:Pharyngitis / Q000276:immunology / Q000382:microbiology; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D013290:Streptococcal Infections / Q000276:immunology*; D013297:Streptococcus pyogenes / Q000235:genetics / Q000276:immunology*; D013300:Streptokinase / Q000032:analysis
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D015415:Biomarkers; D002352:Carrier Proteins; D016056:Immunodominant Epitopes; D007074:Immunoglobulin G; D010455:Peptides; D011994:Recombinant Proteins; C014689:streptococcal M protein; D000989:Antistreptolysin; D013300:Streptokinase