title: Reduced frequency of HLA-DQ6 in individuals with a positive direct antiglobulin test.
abstract: BACKGROUND
  The association between HLA class II antigens and the production of red cell autoantibodies was investigated in this study.
  
  
  METHODS
  Thirty-one individuals with a positive direct antiglobulin test (DAT) and 85. DAT-negative controls (cadaveric organ donors) were typed using a DNA-based method for class II HLA typing, that is, the polymerase chain reaction with sequence-specific primers. Amplified HLA alleles corresponding to the serologic specificities DR 1-18 and DQ 1-9 were identified.
  
  
  RESULTS
  Analysis of DR and DQ frequencies showed that HLA-DQ6 was less frequent in DAT-positive individuals (19% vs. 53% in the control population), with a p value of 0.0014 and a corrected p value of 0.059, and relative risk of 0.23 (95% Cl = 0.09-0.58). The frequency of HLA-DQ6 was higher in asymptomatic DAT-positive blood donors (n = 8, 38% DQ6 positive, p = 0.48) than in DAT-positive hospital and clinic patients (n = 23, 13% DQ6 positive, corrected p value = 0.030, relative risk = 0.13, 95% Cl = 0.04-0.41), 96 percent of whom had evidence of clinical hemolysis.
  
  
  CONCLUSIONS
  This study demonstrates that HLA-DQ6 may have a negative association with a positive DAT result in patients with evidence for hemolysis, and may be a resistance antigen for clinically relevant red cell autoantibodies.
authors.affiliation: School of Medicine, University of California, San Diego, La Jolla, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wang-Rodriguez
authors.forename: A
authors.initials: A
authors.lastname: Rearden
mesh_terms: D000328:Adult; D000368:Aged; D000483:Alleles; D000744:Anemia, Hemolytic, Autoimmune / Q000097:blood / Q000235:genetics* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D003298:Coombs Test; D004198:Disease Susceptibility; D005260:Female; D005787:Gene Frequency; D005802:Genes, MHC Class II; D006683:HLA-DQ Antigens / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D006650:Histocompatibility Testing; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational
chemical_list: D001323:Autoantibodies; D006683:HLA-DQ Antigens; C063831:HLA-DQ6 antigen