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H antigen

H antigen can refer to one of various types of antigens having diverse biological functions. H antigen is located on 19th chromosome :

  • Also known as substance H, a precursor to each of the ABO blood group antigens, apparently present in all people except those with the Bombay Blood phenotype (see Hh antigen system)
  • Histocompatibility antigen, a major factor in graft rejection. Even when Major Histocompatibility Complex genotype is perfectly matched, can cause slow rejection of a graft.
    • major H antigens "encode molecules that present foreign peptides to T cells"
    • minor H antigens "present polymorphic self peptides to T cells". Includes, e.g. the H-Y antigen
  • a bacterial flagellar antigen