ABO genotyping in Italian blood donors

Traditional ABO blood group serology is based on the immunoreactivity of antisera with the carbohydrate A, B and H antigens. Progress in the molecular biology of the ABO system has recognized the molecular basis of the red cell (RBC) antigens and has provided a genetic model for ABO polymorphism at the molecular level. Recently, this genetic model was tested in a large number of individuals.

In this study we applied DNA analysis to determine the frequency of ABO genotypes in a group of blood donors for whom the ABO type was known. Two hundred and fifty healthy Italian blood donors were analyzed using polymerase chain reaction (PCR) to amplify two different regions of genomic DNA, each of which contained a different nucleotide polymorphism. The amplified product was digested with 4 restriction enzymes that revealed differences among A, B and O individuals. To analyze the genes at polymorphic sites 261 and 703 we used the restriction enzymes BstE II and Kpn I, and Hpa II and Alu I and compared the PCR determined genotypes to serologically determined phenotypes.

The results were consistent for all unrelated individuals; however, 2 of 100 individuals with the 0 phenotype carried one allele that differed from the proposed genetic model. This novel O allele, termed 0(2) by Yamamoto et al., was found in our series with a frequency of 1%. The blood group AB0 genotype of 250 healthy Italian blood donors was: 13 AA/AO(2), 37 AO(1), 11 BB, 39 B0(1), 50 AB, 98 0(1)0(1) and 2 0(1)0(2). This method should be applicable not only in forensic medicine but also in immunohematology when serology fails.