Another example of a KEL1 variant red cell phenotype due to a threonine to serine change at position 193 of Kell glycoprotein

Abstract

Healthy subjects whose red blood cells (RBCs) react variably with anti-KEL1, but strongly express other Kell blood group antigens, have been described and called KEL1 variant. A 53-year-old Caucasian blood donor was identified whose RBCs reacted with three monoclonal and two polyclonal anti-KEL1 and did not react with two monoclonal and one polyclonal anti-KEL1. The molecular basis of this phenotype was investigated. Genomic white blood cell DNA was analyzed for KEL*1/2 genotype by utilizing sequence-specific primers and polymerase chain reaction. In addition, the region of the KEL*1/2 polymorphism at position 578 of KEL was analyzed by DNA sequencing. Genotyping of the donor with the KEL1 variant phenotype revealed that he was KEL*2 homozygous. Sequencing revealed one typical KEL*2 allele and a KEL*2 allele with an adenosine (A) to thymidine (T) substitution at position 577 that predicted a threonine to serine change at position 193. It is not known if this phenotype is clinically relevant, but for at least some genotyping applications probes that identify this polymorphism should be used and anti-KEL1 should be tested for reactivity to this allele.