The P1H antigen and antibody

P1H. a newly discovered compound antigen associated with both the ABO and P systems, occurs in approximately percent of Natal (South African) blacks. The compound antigen, is evident only when the red cells have exceptionally strong expression of both and H antigens, and it is apparently a dominant character. The antigen is thought to originate by steric rearrangement in the molecule, or to be the product of competition between pl and H gene transferases for the available paragloboside The corresponding antibody, anti-P1H, has been made by both P1 and P2 people and is a weak cold agglutinin It is not adsorbed by red cell, carrying either strongly expressed P1 or H antigens but is adsorbed by and eluted from P1H+ red cells sensitized by anti- P1H. The antibody is, inhibited by P1 but not by H. Lewis, or Sda substances.