Frequency of Mi (MNS7) and Classification of Mi-Positive Hybrid Glycophorins in an Australian Blood Donor Population.

Background: MNS blood group system genes and share a high degree of sequence homology and gene structure. Homologous exchanges between and form hybrid genes encoding hybrid glycophorins GP(A-B-A) and GP(B-A-B). Over 20 hybrid glycophorins have been characterised. Each has a distinct phenotype defined by the profile of antigens expressed including Mi. Seven hybrid glycophorins carry Mi and have been reported in Caucasian and Asian population groups. In Australia, the population is diverse; however, the prevalence of hybrid glycophorins in the population has never been determined. The aims of this study were to determine the frequency of Mi and to classify Mi-positive hybrid glycophorins in an Australian blood donor population.

Method: Blood samples from 5,098 Australian blood donors were randomly selected and screened for Mi using anti-Mi monoclonal antibody (CBC-172) by standard haemagglutination technique. Mi-positive red blood cells (RBCs) were further characterised using a panel of phenotyping reagents. Genotyping by high-resolution melting analysis and DNA sequencing were used to confirm serology.

Result: RBCs from 11/5,098 samples were Mi-positive, representing a frequency of 0.22%. Serological and molecular typing identified four types of Mi-positive hybrid glycophorins: GP.Hut ( = 2), GP.Vw ( = 3), GP.Mur ( = 5), and 1 GP.Bun ( = 1). GP.Mur was the most common.

Conclusion: This is the first comprehensive study on the frequency of Mi and types of hybrid glycophorins present in an Australian blood donor population. The demographics of Australia are diverse and ever-changing. Knowing the blood group profile in a population is essential to manage transfusion needs.