TMP-reactive autoantibodies in human SLE sera demonstrate thymine-dependent oligonucleotide specificity

Area of Science:

• Immunology
• Molecular Biology
• Rheumatology

Background:

• Autoantibodies against single-stranded DNA (ssDNA) are hallmarks of systemic lupus erythematosus (SLE).
• The heterogeneity of these autoantibodies complicates understanding their specific targets and pathogenic roles.
• Characterizing antibody specificity is crucial for diagnosing and treating lupus.

Purpose of the Study:

• To investigate the fine specificity of anti-ssDNA autoantibodies in lupus patients.
• To identify specific nucleotide or sequence preferences within the anti-ssDNA antibody repertoire.
• To determine if thymidine monophosphate (TMP) is a significant antigenic determinant for a subset of these antibodies.

Main Methods:

• Fractionation of serum autoantibodies from lupus patients using TMP-agarose affinity chromatography.
• Enzyme-linked immunosorbent assay (ELISA) to assess antibody binding to various nucleotide conjugates and DNA types (ssDNA, dsDNA).
• Competition-inhibition studies using TMP-enriched oligonucleotides and polynucleotides of varying sequences and lengths.

Main Results:

• Antibodies purified on TMP-agarose demonstrated specific binding to TMP-BSA and ssDNA, but not to other nucleotide conjugates or double-stranded DNA (dsDNA).
• Competition-inhibition assays confirmed that TMP-containing oligonucleotides and polynucleotides were preferred antigens.
• Antigenicity of TMP-based oligonucleotides increased with their size (length), indicating a size- and TMP-dependent specificity.

Conclusions:

• A distinct subset of autoantibodies in lupus patients exhibits specificity for TMP-dependent oligonucleotide sequences.
• These findings highlight the importance of nucleotide composition and size in defining the antigenic targets of anti-ssDNA autoantibodies.
• This TMP-specificity may represent a unique epitope targeted by pathogenic autoantibodies in SLE.