title: Natural anti-A and anti-B of the ABO system: allo- and autoantibodies have different epitope specificity.
abstract: BACKGROUND
  According to Landsteiner's law, alloantibodies are prevalent and autoantibodies are absent in the ABO blood group system. However, one study (Spalter et al., Blood 1999;93:4418-24) has suggested that low-affinity ABO autoantibodies, mitigated by anti-idiotypic immunoglobulins are also prevalent, while another publication (Rieben et al., Eur J Immunol 1992;22:2713-7) shows that humans do not have B-lymphocytes capable of producing immunoglobulin G ABO autoantibodies.
  
  
  METHODS
  We used hapten-specific chromatography to isolate allo- and autoantibodies from pools of A or B serum and then characterized the resultant antibodies against a wide range of ABO and related glycoconjugates.
  
  
  RESULTS
  We found that the apparent autoantibodies are directed against blood group A or B disaccharides, without consideration for the presence of fucose, but requiring the absence of elongating sugar X in composition of Gal(NAc)α1-3(Fucα1-2)Galβ1-X-terminated carbohydrate chain. In contrast, ABO alloantibodies required a minimum trisaccharide Gal(NAc)α1-3(Fucα1-2)Gal epitope and recognize the elongated type-specific tetrasaccharides. Furthermore, alloantibodies appear to be a small set of specific yet crossreactive antibodies that detect all backbone types of A or B antigens, rather than being a collection of specific antibodies, each of which detects a different type of A or B antigen.
  
  
  CONCLUSIONS
  Apparent ABO autoantibodies appear to have no natural human target.
authors: Shemyakin Institute of Bioorganic Chemistry RAS, Moscow, Russia.
authors: Polina
authors: P
authors: Obukhova
authors: Elena
authors: E
authors: Korchagina
authors: Stephen
authors: S
authors: Henry
authors: Nicolai
authors: N
authors: Bovin
mesh_terms: D000017:ABO Blood-Group System / Q000276:immunology*; D000328:Adult; D001323:Autoantibodies / Q000276:immunology* / Q000302:isolation & purification; D000939:Epitopes; D006801:Humans; D007518:Isoantibodies / Q000276:immunology* / Q000302:isolation & purification; D011134:Polysaccharides / Q000378:metabolism
chemical_list: D000017:ABO Blood-Group System; D001323:Autoantibodies; D000939:Epitopes; D007518:Isoantibodies; D011134:Polysaccharides