title: Molecular Basis of KELnull Phenotype in Brazilians.
abstract: BACKGROUND
  KELnull (K0) persons can produce clinically significant anti-KEL5 antibody after transfusion and/or pregnancy, requiring K0 blood transfusion when indicated. 37 K0 alleles have been reported in studies over different populations, but none in Amerindian-Caucasian descendants from South America. The aim of this study was to identify the molecular basis of K0 phenotype in Brazilians.
  
  
  METHODS
  We investigated three K0 samples from different Brazilian blood banks (Recife, Manaus, and Vila Velha) in women with anti-KEL5. KEL antigen typing was performed by serologic techniques, and the K0 status was confirmed by flow cytometry. PCR-RFLP and DNA sequencing of the KEL coding and exon-intron regions were also performed.
  
  
  RESULTS
  RBCs of the 3 patients were phenotyped as KEL:-1,-2,-3,-4,-7. The 3 patients had the same KEL*02/02 genotype and were negative for KEL*02.03 and KEL*02.06 alleles. The Recife K0 patient was homozygous for IVS16 + 1g>a mutation (KEL*02N.31 allele). The flow cytometry with anti-KEL1, anti-KEL2, anti-KEL3, anti-KEL4, and anti-CD238 confirmed the K0 phenotype. In addition, we found the c.10423C>T mutation (KEL*02N.04 allele) in both the Manaus K0 and the Vila Velha K0 patients.
  
  
  CONCLUSIONS
  This report represents the first study of K0 molecular basis performed in Amerindian-Caucasian descendants from South America.
authors.affiliation: Universidade Federal de São Paulo, Hematology and Transfusion Medicine Department, São Paulo, SP, Brazil.
authors.forename: Edmir
authors.initials: E
authors.lastname: Boturão-Neto
authors.affiliation: Universidade Federal de São Paulo, Hematology and Transfusion Medicine Department, São Paulo, SP, Brazil.
authors.forename: Mihoko
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Universidade Federal de São Paulo, Hematology and Transfusion Medicine Department, São Paulo, SP, Brazil.
authors.forename: Akemi Kuroda
authors.initials: AK
authors.lastname: Chiba
authors.affiliation: Universidade Federal de São Paulo, Hematology and Transfusion Medicine Department, São Paulo, SP, Brazil.
authors.forename: Elisa Yuriko Sugano
authors.initials: EY
authors.lastname: Kimura
authors.affiliation: Fundação HEMOPE, Hemotherapy Department, Recife, PE, Brazil.
authors.forename: Maria do Carmo Valgueiro Costa
authors.initials: Mdo C
authors.lastname: de Oliveira
authors.affiliation: Fundação HEMOPE, Hemotherapy Department, Recife, PE, Brazil.
authors.forename: Cláudia Lumack
authors.initials: CL
authors.lastname: do Monte Barretto
authors.affiliation: Fundação HEMOPE, Hemotherapy Department, Recife, PE, Brazil.
authors.forename: Mércia Maria Alves
authors.initials: MM
authors.lastname: Nunes
authors.affiliation: Fundação Hospitalar de Hematologia e Hemoterapia do Estado do Amazonas, Immunohematology Department, Manaus, AM, Brazil.
authors.forename: Sérgio Roberto Lopes
authors.initials: SR
authors.lastname: Albuquerque
authors.affiliation: Universidade Federal do Espírito Santo, Internal Medicine Department, Vila Velha, ES, Brazil.
authors.forename: Marcos Daniel
authors.initials: MD
authors.lastname: de Deus Santos
authors.affiliation: Universidade Federal de São Paulo, Hematology and Transfusion Medicine Department, São Paulo, SP, Brazil.
authors.forename: José Orlando
authors.initials: JO
authors.lastname: Bordin
keywords: KELnull alleles; KELnull phenotype; Kell blood group system