title: Repertoire of human natural anti-glycan immunoglobulins. Do we have auto-antibodies?
abstract: BACKGROUND
  Profiling of donor's antibodies using glycan arrays demonstrated presence of antibodies capable of binding to >100 mammalian glycans or their fragments. For example, relatively high binding to Galα1-4Galβ1-4GlcNAc (P(1)), Galα1-4Galβ1-4Glc (P(k)), Galβ1-3GlcNAc (Le(c)), 4-O-SuGalβ1-4GlcNAc, and GalNAcα1-3GalNAc (Fs) was found in all tested individuals. Affinity isolation using hapten-specific chromatography in combination with epitope mapping revealed their glycotopes. Notably, a significant part of the antibodies was capable of recognizing a fragment of larger glycans, for example, -Galβ1-4Glc of glycolipids, or Fucα1-3GlcNAc motif of Le(X)/Le(Y) antigens. Their epitope specificity did not vary between different healthy individuals. Nominally, all the mentioned immunoglobulins could be classified as auto-antibodies.
  
  
  METHODS
  In this work we re-evaluated results published earlier and analyzed new data to address the question why autologous antibodies found in healthy individuals do not cause severe auto-immune reactions.
  
  
  RESULTS
  In all cases the presumably "auto" antibodies were found to bind short fragments "subtracted" from larger glycans whereas recognition of the same fragment in the context of the whole natural chain was completely abolished. Thus, in spite of numerous formally positive signals observed on the printed glycan array, we are yet unable to identify in blood serum of healthy individuals true auto-antibodies capable of binding carbohydrate chains in their naturally occurring form.
  
  
  CONCLUSIONS
  The identified natural anti-glycan antibodies were found to be specific, high-titer and population conservative immunoglobulins - all of this suggesting as yet unknown biological role(s) of the studied proteins. This article is part of a Special Issue entitled Glycoproteomics.
authors.affiliation: Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russian Federation. bovin@carb.ibch.ru
authors.forename: Nicolai
authors.initials: N
authors.lastname: Bovin
authors.forename: Polina
authors.initials: P
authors.lastname: Obukhova
authors.forename: Nadezhda
authors.initials: N
authors.lastname: Shilova
authors.forename: Evgenia
authors.initials: E
authors.lastname: Rapoport
authors.forename: Inna
authors.initials: I
authors.lastname: Popova
authors.forename: Maksim
authors.initials: M
authors.lastname: Navakouski
authors.forename: Carlo
authors.initials: C
authors.lastname: Unverzagt
authors.forename: Marko
authors.initials: M
authors.lastname: Vuskovic
authors.forename: Margaret
authors.initials: M
authors.lastname: Huflejt
mesh_terms: D001323:Autoantibodies / Q000032:analysis* / Q000097:blood; D002240:Carbohydrate Sequence; D015331:Cohort Studies; D018604:Epitope Mapping; D054794:Glycomics / Q000379:methods; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis* / Q000097:blood; D008954:Models, Biological; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000097:blood / Q000276:immunology*; D040081:Protein Array Analysis; D011485:Protein Binding
chemical_list: D001323:Autoantibodies; D007136:Immunoglobulins; D011134:Polysaccharides