Cloning and genetic characterization of blood group carrier molecules and antigens

Based on the astounding pace of growth in the field of molecular biology over the last 2 decades, we are now able to consider the allogenicity of transfused blood products in genetic terms. In this sense, the allogenic barriers to the transfusion-based transplantation are defined by differences between those portions of the donor and recipient genomes that define the antigenicity and immune response to transfused cells. The genetic basis of the major histocompatibility complex barrier described earlier is because of well-characterized transcription from a polymorphic locus on chromosome 6 in nonerythroid cells. In contrast, the allo-barrier of ABO-matched RBC transfusion is the result of differences in over 2 dozen independent genes expressed during erythropoiesis that encode a wide variety of molecules important in membrane biology. Variability in the structure of those genes among separate donors often provides the molecular basis of many blood group antigens and phenotypes. This article reviews our current knowledge of the human blood group systems in genetic terms, focusing on strategies used to identify the relevant genes and their polymorphisms.