Miltenberger blood group antigen subtype III (Mi.III) supports Wr(b) expression

Background and Objectives Miltenberger blood group antigens belong to the complex MNS system. Miltenberger antigen subtype III (Mi.III) was previously found to promote the expression of band 3. Here, we investigated whether the direct interaction between band 3 and Mi.III‐specific Gp.Mur (a glycophorin B‐A‐B hybrid) might affect the expression of related blood group antigens such as the Wright b (Wr^b) antigen. Materials and Methods (1) Band 3 genes of Mi.III+ and non‐Mi.III (control) donors were sequenced to determine the genotypes of the Wright antigens. (2) The expression levels of Wr^b, glycophorin A (GPA) and band 3 in Mi.III and the control erythrocytes were quantitatively assessed by flow cytometry. Results Mi.III erythrocytes expressed 22·5 ± 6·6% more Wr^b antigen than the control cells. The increase in Wr^b in Mi.III cells was independent of their GPA levels. Conclusion The elevated Wr^b levels in Mi.III RBCs were likely linked to their higher band 3 levels. Higher band 3 densities on the Mi.III+ cell surface conceivably could drive complex formation between band 3 and GPA/Gp.Mur, thereby increasing the expression of Wr^b.