Blood group antigen
(Science: haematology, immunology) The set of cell surface antigens found chiefly, but not solely, on blood cells.
More than fifteen different blood group systems are recognised in humans. There may be naturally occurring antibodies without immunisation, especially in the case of the ABO system and matching blood groups is important for safe transfusion.
in most cases the antigenic determinant resides in the carbohydrate chains of membrane glycoproteins or glycolipids.
See: rhesus, Duffy, Kell, lewis and MN.