title: Polymerase chain reaction based C4AQ0 and C4BQ0 genotyping: association with systemic lupus erythematosus in southwest Han Chinese.
abstract: OBJECTIVE
  To investigate the association of complement C4 null genes (C4Q0, including C4AQ0 and C4BQ0) and C2 gene with systemic lupus erythematosus (SLE) in southwest Han Chinese; 136 patients with SLE and 174 matched controls were genotyped.
  
  
  METHODS
  C4 null genes were determined by a polymerase chain reaction (PCR) procedure with sequence specific primers (PCR-SSP). The 2 bp insertion in exon 29, which was previously identified in non-Chinese populations and caused defective C4A genes, was directly typed by sequencing the whole exon 29 using exon specific primers. The exon 6 of complement C2 was also sequenced in both the patients and controls.
  
  
  RESULTS
  The frequency of homozygous C4AQ0 allele was 12.5% (17/136) in patients with SLE compared with 1.1% (2/174) in controls (p<0.001, odds ratio (OR)=12.286, 95% confidence interval (95% CI) 2.786 to 54.170). There was no significant difference for homozygous C4BQ0 allele between patients with SLE and controls (p=0.699). Patients with the C4AQ0 gene had an increased risk of acquiring renal disorder, serositis, and anti-dsDNA antibodies compared with those without C4AQ0 (for renal disorder, p=0.018, OR=8.951, 95% CI 1.132 to 70.804; for serositis, p=0.011, OR 4.891, 95% CI 1.574 to 15.198; for anti-dsDNA, p=0.004, OR 7.630, 95%CI 1.636 to 35.584). None of the patients or controls had the 2 bp insertion in exon 29 of the C4 gene. The type I C2 deficiency was not detected in the 310 samples.
  
  
  CONCLUSIONS
  It is suggested that deficiency of C4A (not due to a 2 bp insertion in exon 29), but not C4B or C2, may be a risk factor for acquiring SLE in south west Han Chinese; this results in increased risk of renal disorder, serositis, and anti-dsDNA antibodies in patients with SLE. Racial differences seem to be relevant in susceptibility to SLE
authors.affiliation: Laboratory of Molecular Evolution and Genome Diversity, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, People's Republic of China.
authors.forename: X-Y
authors.initials: XY
authors.lastname: Man
authors.forename: H-R
authors.initials: HR
authors.lastname: Luo
authors.forename: X-P
authors.initials: XP
authors.lastname: Li
authors.forename: Y-G
authors.initials: YG
authors.lastname: Yao
authors.forename: C-Z
authors.initials: CZ
authors.lastname: Mao
authors.forename: Y-P
authors.initials: YP
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D002681:China / Q000208:ethnology; D003175:Complement C2 / Q000235:genetics*; D003181:Complement C4 / Q000235:genetics*; D015934:Complement C4a / Q000235:genetics; D015935:Complement C4b / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D005787:Gene Frequency; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000208:ethnology / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods
chemical_list: D003175:Complement C2; D003181:Complement C4; D015934:Complement C4a; D015935:Complement C4b