Genomic analyses of KEL alleles in alloimmunized thalassemia patients from Iran

Serological methods are unreliable for red blood cells (RBCs) antigen typing in multi-transfused thalassemia patients due to the presence of donor RBCs in the recipient's circulation and interfering antibodies. Kell blood group system is important in transfusion medicine and Kell antibodies have shown as the most prevalent antibodies in thalassemia patients. We intended to determine the genotype of Kell antigens among Iranian alloimmunized thalassemia patients using molecular methods and compare the results with serological phenotyping.

Two hundred thalassemia patients participated in this study. Blood group phenotype was performed by the serological method, while the genotype was determined for KEL*01, KEL*02, KEL*03, and KEL*04 alleles using PCR-Sequence Specific Primer (PCR-SSP) method. The genotypes of patients with incompatibility between phenotype and genotype were re-evaluated by Restriction Fragment Length Polymorphism-PCR (RFLP-PCR) and confirmed by DNA sequencing in all cases.

Ten patients were found with discrepancies between genotype and phenotype; however, there was a complete agreement between the results of SSP-PCR, RFLP-PCR, and DNA sequencing. Six discrepancies were found in the KEL*01/KEL*02 allele when serologically phenotyped as K-k+. One patient with K-k- and three patients with Kpa-Kpb + phenotype were identified as KEL*01/KEL*02 and KEL*03/KEL*04, respectively.

It can be concluded that molecular genotyping is more reliable compared with the serological method, especially in the patients who have received multiple transfusions. Therefore, using a combination of these techniques can lead to a better matched transfusion in these patients.