An easy and efficient strategy for KEL genotyping in a multiethnic population

Abstract

Background: The Kell blood group system expresses high and low frequency antigens with the most important in relation to transfusion including the antithetic KEL1 and KEL2; KEL3 and KEL4; KEL6 and KEL7 antigens. Kell is a clinically relevant system, as it is highly immunogenic and anti-KEL antibodies are associated with hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Although required in some situations, Kell antigen phenotyping is restricted due to technical limitations. In these cases, molecular approaches maybe a solution. This study proposes three polymerase chain reaction genotyping protocols to analyze the single nucleotide polymorphisms responsible for six Kell antithetic antigens expressed in a Brazilian population.

Methods: DNA was extracted from 800 blood donor samples and three polymerase chain reaction-restriction fragment length polymorphism protocols were used to genotype the KEL*1/KEL*2, KEL*3/KEL*4 and KEL*6/KEL*7 alleles. KEL*3/KEL*4 and KEL*6/KEL*7 genotyping was standardized using the NlaIII and MnlI restriction enzymes and validated using sequencing. KEL*1/KEL*2 genotyping was performed using a previously reported assay.

Results: KEL genotyping was successfully implemented in the service; the following distribution of KEL alleles was obtained for a population from southeastern Brazil: KEL*1 (2.2%), KEL*2 (97.8%), KEL*3 (0.69%), KEL*4 (99.31%), KEL*6 (2.69%) and KEL*7 (97.31%). Additionally, two individuals with rare genotypes, KEL*1/KEL*1 and KEL*3/KEL*3, were identified.

Conclusion: KEL allele genotyping using these methods proved to be reliable and applicable to predict Kell antigen expressions in a Brazilian cohort. This easy and efficient strategy can be employed to provide safer transfusions and to help in rare donor screening.

Keywords: Erythrocytes; Gene frequency; Kell blood-group system; Molecular biology; Polymerase chain reaction.

Figure 1

polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) electrophoresis gels A. KEL*1/KEL*2 genotyping where sample in lane 1 was genotyped as KEL*1/KEL*2, in lane 2 as KEL*1/KEL*1, and in lane 3 as KEL*2/KEL*2 B. KEL*3/KEL*4 genotyping where sample in lane 4 was genotyped as KEL*4/KEL*4, in lane 5 as KEL*3/KEL*4, and in lane 6 as KEL*3/KEL*3 C. KEL*6/KEL*7 genotyping where sample in lane 7 was genotyped KEL*7/KEL*7 and in lane 8 as KEL*6/KEL*7 M identifies the 50 bp molecular marker and PCR identifies PCR products