BIOLOGY OF THE HUMAN GLYCOPHORIN BLOOD GROUP ANTIGENS

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Glycophorin A is the major glycoprotein on the human erythrocyte surface and contains one N-glycan and multiple O-glycans. Glycophorin B, a highly homologous glycoprotein on human erythrocytes, contains only O-glycans. Although appropriate glycosylation is crucial for cell surface expression of glycophorin A, the mechanism responsible for this effect is not understood. Glycophorin A and B are important in the practice of transfusion medicine since they carry multiple human blood group antigens, and antibodies to these antigens can cause hemolytic transfusion reactions, hemolytic disease of the newborn,a nd autoimmune hemolytic anemia. However, there have been few studies examining the fine specificity of binding of human polyclonal and mouse monoclonal antibodies to these molecules. Glycophorins A and B are also of medical importance because they serve as erythrocyte surface receptors for the invasion of Plasmodium falciparum malaria merozoites. Due to the difficulty in obtaining mutant glycophorin molecules with defined variaitons in amino acid sequence and oligosaccharide structure, a detailed understanding of this host cell- parasite interaction is not yet available. The goals of the current proposal are to study the cell biology, immunology, and receptor function of the human blood group glycophorin antigens by: 1. determining the role that the N-glycans and O-glycans play in intracellular transport of glycophorin A. 2. using recombinant DNA approaches to examine the murine and human immune response to glycophorins A and B, and 3. determining the peptide and carbohydrate portions of glycophorins A and B that are recognized by human malaria parasites. These goals will be achieved by using a series of stably transfected cell lines expressing cDNA of wild type or variant glycophorin A or B. New mutant glycophorin A and B cDNAs will be constructed by site-directed mutagenesis. B=y expressing the cDNAs in both normal Chinese hamster ovary fibroblasts and those with defects in glycosylation, it is possible to create variant glycophorins that differ in both amino acid and carbohydrate sequence. Phage display libraries will be constructed to examine the murine immune response to glycophorin A. This will determine whether the immune response is restricted and will also result in athe construction of new clinically useful serological reagents. In summary, these studies will result in greater understanding of the cell biology, immunology, and receptor function of glycophorins A and B.