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Three Cases of Anti-K and the KEL Gene Frequency in the Korean Population

Background: Anti-K is one of the most significant unexpected antibodies that cause hemolytic transfusion reactions. Individuals with anti-K have to be transfused with K antigen-negative red cells. Although Koreans rarely have the K antigen, we have detected three cases of anti-K and we analyzed the Kell blood group genotypes for the KEL*1/KEL*2 alleles at the same time. Methods: We analyzed the KEL*1/KEL*2 allele genotypes from 261 blood donors at Seoul National University Bundang Hospital. Kell genotyping were carried out using polymerase chain reaction (PCR) and restriction enzyme length polymorphism (RFLP). Identification of anti-K was performed using three kinds of methods; 37 o C albumin, an anti-human globulin phase tube, a bead cassette and a gel card. Three cases of anti-K also underwent PCR with a sequence specific primer (SSP) for Kell genotyping. For comparison, the KEL*1 allele (698C ＞ T) was synthesized by site-directed-mutagenesis. Results: All 261 donors were KEL*2/KEL*2 homozygotes and a digested KEL*1 allele was not found. The three patients with anti-K were also KEL*2/KEL*2 homozygotes and the reactivities of the anti-K identification test were the same. Conclusion: The KEL gene frequency for the KEL*1/KEL*2 allele corresponded with that of the Kell phenotype, as was previously reported. We experienced three cases of anti-K and two out of the three were assumed that they had been transfused with the K antigen-positive blood of foreigners. This study revealed that the possibility of anti-K alloimmunization and hemolytic transfusion reactions cannot be excluded in Koreans. (Korean J Blood Transfus 2011;22:31-37)