Antifilaggrin antibodies in serum and synovial fluid samples of patients with rheumatoid arthritis show similar reactivity pattern towards citrulline containing peptides

Background

Antifilaggrin antibodies are highly specific serological markers of rheumatoid arthritis (RA). They have been shown to comprise a heterogeneous population of antibodies directed at citrullinated peptides. Recent studies suggest that the site of the initial antigenic trigger where these autoantibodies are produced can be localized to the synovial tissue.

Objective

The aim of this study was to compare the recognition patterns of antibodies in paired serum and synovial fluid samples of RA patients toward citrullinated peptide sequences to investigate whether or not they comprise the same antibody population.

Methods

Arginine-rich peptide sequence corresponding to human profilaggrin (amino acid residues 306–324) and sequences with citrulline substitution at different positions were synthesized by mutipin peptide synthesis on solid support. Completely citrullinated variant of the 19-mer peptide and shortened sequences were also produced. The reactivity of these peptides with paired sera and synovial fluid samples of RA patients were determined (n = 25). Results were evaluated statistically using the paired t test.

Results and Conclusion

The results (Table 1) show that the 12–19 amino acid long epitopes are recognized by homogeneous antibody population present in serum and synovial fluid, whereas the reactivities toward short citrullinated sequences differs significantly.

Table 1 Comparison of the reactivities of antibodies in paired serum and synovial fluid samples