Red cell antigens on band 3 and glycophorin A

Band 3 and glycophorin A (GPA) are the two most abundant integral proteins of the red cell membrane, being present in approximately 10(6) copies per c ell, The main functions of band 3 are membrane anion transport and maintena nce of red cell membrane stability through interaction with the cytoskeleto n, GPA plays an important role in prevention of red cell aggregation in the circulation and contribution to the glycocalyx, The extracellular domains of both proteins are highly polymorphic, Band 3 carries the antigens (curre ntly 19) of the Diego blood group system and GPA and glycophorin B the anti gens (currently 43) of the MNS system, There is substantial evidence that b and 3 and GPA associate in the red cell membrane and the Wr(b) antigen, alt hough a product of the band 3 gene, is known to require a complex of GPA an d band 3 for normal expression, The discovery of a novel GPA mutation (Ala6 5-->Pro) giving rise to aberrant Wr(b) expression has been informative with regard to the site of interaction of the two proteins. The extensive array of GPA-related antigens is largely due to genetic events between two close ly linked genes and different genetic mechanisms can give rise to the same antigen. This is in contrast to the antigens on band 3 which are exclusivel y due to single nucleotide mutations in the band 3 gene. (C) 2000 Harcourt Publishers Ltd.