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.1042C>T mutation (KEL∗02N.04 allele) in both the Manaus K0 and the Vila Velha K0 patients. Conclusion: This report represents the first study of K0 molecular basis performed in Amerindian-Caucasian descendants from South America.