Restricted epitope recognition by precipitin-negative anti-La/SS-B-positive sera

Arthritis Rheum. 1992 Jun;35(6):663-6. doi: 10.1002/art.1780350609.


Objective: To determine whether anti-La/SS-B-positive sera that are precipitin negative show a distinct B cell epitope pattern.

Methods: Serum reactivity was tested with recombinant La/SS-B fusion proteins.

Results: Among the 18 precipitin-negative anti-La/SS-B-positive sera, reactivity was confined to the full-length recombinant protein (La33.3) in 8 (44%); 5 of 18 (28%) reacted only with La33.3 and with the first 107 N-terminal amino acids (LaA), and 4 (22%) reacted with La33.3, LaA, and the middle region of the La molecule (LaC; amino acids 111-242). One serum reacted with La33.3 and LaC. None of the 18 precipitin-negative sera was positive on a carboxy-terminal fragment (LaL2/3; amino acids 346-408). In contrast, all 26 precipitin-positive anti-La/SS-B-positive sera reacted with La33.3, LaA, and LaC, and 92% reacted with LaL2/3. Rheumatoid factor and serum IgG levels were significantly lower in the precipitin-negative group, providing further evidence of a distinct serologic subset.

Conclusion: The restricted epitope recognition by these sera may explain the lack of precipitin formation and may represent an early autoantibody response to La/SS-B.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autoantibodies / blood*
  • Autoantigens / immunology*
  • B-Lymphocytes / immunology
  • Enzyme-Linked Immunosorbent Assay
  • Epitopes
  • Humans
  • Immunoglobulin G / analysis
  • Precipitin Tests
  • Rheumatoid Factor / analysis
  • Ribonucleoproteins*


  • Autoantibodies
  • Autoantigens
  • Epitopes
  • Immunoglobulin G
  • Ribonucleoproteins
  • SS-B antigen
  • Rheumatoid Factor