Mapping of novel autoreactive epitopes of the diabetes-associated autoantigen IA-2

Clin Exp Immunol. 2000 Nov;122(2):157-63. doi: 10.1046/j.1365-2249.2000.01352.x.


IA-2, a member of the tyrosine phosphatase family, has been identified as a dominant autoantigen in type 1 diabetes. To define humoral IA-2 epitopes, we generated a panel of IA-2 deletion mutants and chimeric proteins using the highly homologous tyrosine phosphatase-like protein IA-2beta. Analysis of autoantibody reactivity in 111 IA-2 antibody positive sera from patients with type 1 diabetes revealed that humoral epitopes cluster to several domains of the intracytoplasmic part of IA-2 [IA-2ic, amino acid (aa) 604-979]. Immunodominant epitopes were found in the first N-terminal 73 amino acids (56% positive), in the middle domain residing between residues 699-874 (45% positive) and the C-terminus depending on the presence of aa 931-979 (at least 37% positive). Competition experiments with overlapping peptides revealed that autoantibody binding towards the N-terminus was dependent on residues 621-628. In the C-terminal domain, two novel conformation-dependent epitopes were identified. The first epitope requires the presence of the C-terminal part of IA-2 (aa 933-979) and an IA-2-specific region between residues 771-932. Reactivity against the second epitope was dependent on intact C-terminal domains as well as residues in the middle (aa 887-932) and N-terminal regions (aa 604-771) which are conserved in IA-2 and IA-2beta. We here defined novel autoantigenic determinants in the N-terminus of IA-2 and characterized conformational epitopes residing in the C-terminal region or spanning from C-terminal residues to the N-terminal domain of IA-2ic. The identification of dominant target regions of diabetes-specific autoantibodies may help to elucidate the molecular mechanisms involved in the autoimmunity towards IA-2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibody Specificity
  • Autoantibodies
  • Autoantigens / chemistry
  • Autoantigens / genetics*
  • Autoantigens / immunology*
  • Base Sequence
  • Codon, Initiator / genetics
  • Diabetes Mellitus, Type 1 / enzymology
  • Diabetes Mellitus, Type 1 / genetics*
  • Diabetes Mellitus, Type 1 / immunology*
  • Epitope Mapping
  • Immunodominant Epitopes
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics*
  • Membrane Proteins / immunology*
  • Mice
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1
  • Protein Tyrosine Phosphatases / chemistry
  • Protein Tyrosine Phosphatases / genetics*
  • Protein Tyrosine Phosphatases / immunology*
  • Receptor-Like Protein Tyrosine Phosphatases, Class 8
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / immunology
  • Sequence Deletion
  • Sequence Homology, Amino Acid


  • Autoantibodies
  • Autoantigens
  • Codon, Initiator
  • ICA512 autoantibody
  • Immunodominant Epitopes
  • Membrane Proteins
  • Recombinant Fusion Proteins
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1
  • Protein Tyrosine Phosphatases
  • Ptprn protein, mouse
  • Receptor-Like Protein Tyrosine Phosphatases, Class 8