GYPB encodes glycophorin B, a transmembrane protein that serves as a component of the ankyrin-1 complex involved in erythrocyte membrane stability and shape. The protein carries the S/s antigens and the 'universal' U antigen of the MNS blood group system 1. GYPB is located in a highly homologous gene cluster with GYPA and GYPE, making it susceptible to gene conversion events and hybrid gene formation that can abolish antigen expression 2. The U- phenotype, found in approximately 1% of individuals of African ancestry, results from complete GYPB deletions rather than the previously assumed GYPB*01N deletion 1. GYPB shows significant genetic diversity through hybrid formations with GYPA, creating variants like GP.Mur that express low-incidence antigens such as Mia, particularly common in Southeast Asian populations 3. The protein functions as a receptor for Plasmodium falciparum invasion, with the GYPB*S allele associated with increased susceptibility to malaria infection in Brazilian populations 4. These genetic variations present challenges for blood typing and transfusion compatibility, as current genotyping methods may not accurately predict phenotypes due to complex hybrid gene structures 5. The extensive polymorphism in GYPB reflects evolutionary pressure from infectious diseases, particularly malaria 6.