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Molecular basis for the high-incidence antigens of the Kell blood group system
Background:
The Kell blood group system is complex, containing at least 21 antigens. Some antigens are organized in five allelic sets; other, mostly high-incidence antigens, may be independently expressed. In this study, the molecular basis of five high-incidence antigens in the Kell system are described.
Study Design And Methods:
Genomic DNA sequences from K:-12 (KEL:-12), K:-18 (KEL:-18), K:-19 (KEL:-19), K:-22 (KEL:-22), and TOU-(KEL:-26) persons were sequenced and compared to those from persons with a common Kell phenotype.
Results:
The various Kell phenotypes are due to point mutations that encode amino acid substitutions. In KEL:-18, two mutations in the same codon were noted. In the various phenotypes, the following KEL mutations were noted: in KEL:-12: A1763G, His548Arg; in KEL:-18: C508T and G509A, Arg130Trp and Arg130Gln; in KEL:-19: G1595A, Arg492Gln; in KEL:-22: C1085T, Ala322Val; and in TOU-:G1337A, Arg406Gln. A son of one of the two people with the TOU-phenotype was heterozygous, and he also had the G1337A mutation.
Conclusion:
The high-incidence antigens of the Kell blood group system are characterized by point mutations leading to amino acid substitutions. The KEL:-18 phenotype could be due to either of two point mutations in the same codon replacing arginine with tryptophan or glutamine. TOU was confirmed as a Kell system antigen, and the inheritance of the mutation was demonstrated.