MOLECULAR BASIS OF BLOOD GROUP ANTIGENS

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The objectives are 1) To introduce, to the blood banking community, more exact and convenient methods for determining red cell antigens and identifying antibodies by studying the molecular basis of blood groups with emphasis on the identification of allelic variations. 2) To determine structure/function relationships of some red cell blood groups. 3) To link specific blood group genotypes with disease processes and to understand the basis for the disease. To accomplish these goals we have a collaborative program composed of five projects. Four projects investigate the molecular and cell biology of Rh (Project 1), Kell (Project 2), Duffy (Project 3) and Xg (Project 4) blood groups and project 5 is a clinical component which will apply molecular biology procedures to improving the detection of antibodies and antigens as practiced in a blood bank reference laboratory. Project 1 aims to construct a physical map of the entire Rh locus and determine the order, transcriptional orientation and expression of the major Rh genes. This will lead to understanding the molecular basis of many Rh-related antigens, which is important in blood transfusion, autoimmune hemolytic disease and in hemolytic disease of the newborn (HDN). Kell blood group system incompatibilities also present difficulties in blood transfusion and HDN. Kell antigens reside on a surface exposed glycoprotein with homology to zinc neutral endopeptidases. An aim of Project 2 is to determine the possible role of red cell surface peptidases. Duffy glycoprotein (gpFy), on red cells, acts as a chemokine receptor and also as a binding site for the human malarial parasite Plasmodium vivax. Duffy protein is also found in other tissues such as kidney, lung, thymus and brain. Project 3 aims to determine the function of gpFy in these tissues and, by studying the structure of gpFy, design ways to prevent P. vivax invasion. Project 4 will determine whether Xg blood group is involved in cell interactions. In addition to hematopoietic tissues Xg is found in fibroblasts and is homologous to a product of the MIC 2 gene. Project 5 will use synthetic and recombinant peptides, and allelic-specific transfectants to analyze antibodies in patients. Information on the molecular basis of Rh, Kell, Duffy and Xg blood groups (Projects 1-4) will also be used to introduce new procedures for the identification of blood group antigens. This will impact on pre- natal determination of whether a fetus is at risk for HDN and should be useful in screening for antigen-negative blood for certain immunized patients, such as those with Sickle Cell disease. The five projects are supported by three Core units; administrative, cell culture and cell sorting. The cell culture unit will provide training to investigators, isolate CD34+ cells from hematopoietic tissues, culture progenitor cells and prepare tested reagents for primary hematopoietic cultures. The cell sorting unit will sort and analyze, by flow cytometry, hematopoietic stem cells, committed progenitor cells and other hematopoietic cells with different degrees of differentiation. Overall these 5 projects provide an integrated approach to studying the molecular and cell biology of blood groups and applying the knowledge gained to modernize blood banking procedures and understand the functions of some blood groups and their possible relations to diseases.