Molecular Basis of KELnull Phenotype in Brazilians.

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 KEL02/02 genotype and were negative for KEL02.03 and KEL02.06 alleles. The Recife K0 patient was homozygous for IVS16 + 1g>a mutation (KEL02N.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.

CONCLUSION

This report represents the first study of K0 molecular basis performed in Amerindian-Caucasian descendants from South America.