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.

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.

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.