title: Frequency of Wr(a) antigen and anti-Wr(a) in Brazilian blood donors.
abstract: BACKGROUND
  Wr(a) is a low-incidence antigen, which is antithetical to the high prevalence red blood cell antigen, Wr(b). Anti-Wr(a) is a naturally occurring antibody that is found in approximately 1-2% of blood donors. The aim of this study was to determine the frequency of Wr(a) and anti-Wr(a) in Brazilian blood donors.
  
  
  METHODS
  A total of 1662 Brazilian blood donors were molecularly analyzed using the SNaPshot methodology to determine the WR*A/B alleles and to predict the frequency of the Wr(a) antigen. To detect the anti-Wr(a), samples from 1049 blood donors were analyzed using a gel test with Wr(a+) red blood cells. The serum was treated with dithiothreitol (DTT) to determine the immunoglobulin classes. Immunoglobulin (Ig)-G isotype classification was performed in a gel test using the IgG1/IgG3 card. A monocyte monolayer assay was employed to predict the clinical significance of IgG anti-Wr(a).
  
  
  RESULTS
  Of the 1662 donors, only one sample had the DI*02.03 allele in heterozygous predicting the Wr(a+b+) phenotype. Anti-Wr(a) was detected in 34 (3.24%) samples, 64.7% in females and 35.3% in males. Regarding the immunoglobulin class, eight (23.5%) cases of anti-Wr(a) were classified as IgG and 26 (76.5%) as IgM. Of the eight cases of IgG anti-Wr(a), four were IgG1, two were IgG3 and three anti-Wr(a) were not IgG3 or IgG1, and thus probably IgG2 or IgG4. The results of the monocyte monolayer assay showed that IgG anti-Wr(a) might be of clinical significance.
  
  
  CONCLUSIONS
  This study shows a very low frequency (0.06%) of the Wr(a) antigen in Brazilian blood donors. Additionally, it shows that the frequency of anti-Wr(a) in this population is higher than previously reported.
authors.affiliation: Associação Beneficente de Coleta de Sangue (Colsan), São Paulo, SP, Brazil. Electronic address: janagmuniz@yahoo.com.br.
authors.forename: Janaína Guilhem
authors.initials: JG
authors.lastname: Muniz
authors.affiliation: Associação Beneficente de Coleta de Sangue (Colsan), São Paulo, SP, Brazil.
authors.forename: Carine Prisco
authors.initials: CP
authors.lastname: Arnoni
authors.affiliation: Associação Beneficente de Coleta de Sangue (Colsan), São Paulo, SP, Brazil.
authors.forename: Diana
authors.initials: D
authors.lastname: Gazito
authors.affiliation: Associação Beneficente de Coleta de Sangue (Colsan), São Paulo, SP, Brazil.
authors.forename: Rosangela
authors.initials: R
authors.lastname: de Medeiros Person
authors.affiliation: Associação Beneficente de Coleta de Sangue (Colsan), São Paulo, SP, Brazil.
authors.forename: Tatiana Aparecida de Paula
authors.initials: TA
authors.lastname: Vendrame
authors.affiliation: Associação Beneficente de Coleta de Sangue (Colsan), São Paulo, SP, Brazil.
authors.forename: Flavia Roche Moreira
authors.initials: FR
authors.lastname: Latini
authors.affiliation: Universidade Estadual de Campinas (Unicamp), Campinas, SP, Brazil.
authors.forename: Lilian
authors.initials: L
authors.lastname: Castilho
keywords: Allele frequency; Anti-Wr(a); Diego blood group; Wr(a) antigen