A novel epitope on the C-terminus of SmD1 is recognized by the majority of sera from patients with systemic lupus erythematosus

J Clin Invest. 1998 Aug 15;102(4):754-63. doi: 10.1172/JCI2749.


The SmD1 protein is a specific target for the autoantibody response in SLE. To further analyze this reactivity epitope, mapping was performed with cellulose-bound 13-mer peptides overlapping 10 amino acids (aa). In this initial approach, 4 out of 15 SLE sera recognized more than five overlapping peptides of the SmD1 C-terminus. Therefore, longer oligopeptides of up to 37 aa of this region were generated and probed for as antigens by ELISA. For the SmD1 aa 83-119 polypeptide, there was a striking increase of reactivity with 70.0% positive reactions out of 167 SLE sera. In contrast, 105 healthy control sera were negative, and only 8.3% of sera from patients with other inflammatory diseases (n = 267) exhibited a response, which was of low level only. The anti-SmD183-119 reactivity was significantly higher in anti-dsDNA antibody positive vs. negative sera (P < 0.001) and correlated with disease activity. Four of five human monoclonal anti-dsDNA antibodies also reacted with SmD183-119. The specificity for SmD1 was demonstrated by inhibition experiments and immunization of rabbits with SmD183-119 inducing SmD1-specific antibodies. In conclusion, the SmD183-119 peptide was demonstrated to be an important and highly specific target of the autoimmune response in SLE. The high sensitivity of this ELISA probably depends on a conformational epitope, which appears not to be accessible in the full-size SmD1 protein.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antibody Specificity*
  • Autoantibodies / blood*
  • Autoantigens / chemistry
  • Autoantigens / immunology*
  • Autoimmunity
  • DNA / immunology
  • Enzyme-Linked Immunosorbent Assay
  • Epitopes*
  • Humans
  • Immunoblotting
  • Lupus Erythematosus, Systemic / immunology*
  • Molecular Sequence Data
  • Oligopeptides / chemistry
  • Oligopeptides / immunology
  • Peptide Fragments / chemistry
  • Peptide Fragments / immunology*
  • Protein Conformation
  • Ribonucleoproteins, Small Nuclear*
  • Sensitivity and Specificity
  • snRNP Core Proteins


  • Autoantibodies
  • Autoantigens
  • Epitopes
  • Oligopeptides
  • Peptide Fragments
  • Ribonucleoproteins, Small Nuclear
  • SNRPD1 protein, human
  • snRNP Core Proteins
  • DNA