Scand J Rheumatol. 2003;32(6):337-42
Nissinen R, Paimela L, Julkunen H, Tienari PJ, Leirisalo-Repo M, Palosuo T, Vaarala O.
National Public Health Institute, Department of Molecular Medicine, Biomedicum, Helsinki, Finland.
Antibodies to citrulline-containing epitopes of filaggrin are highly specific for rheumatoid arthritis (RA).
We studied whether the enzyme peptidylarginine deiminase (PAD), responsible for the post-translational modification of peptide-bound arginine residues to citrulline, constitutes an antigen for patients with RA.
IgG antibodies to PAD were measured by enzyme-linked immunosorbent assay (ELISA) in sera from patients with RA, systemic lupus erythematosus (SLE), primary Sjogren syndrome (pSS), multiple sclerosis (MS) and healthy controls.
Compared to healthy controls, raised levels of IgG antibodies to PAD were found in 50 of 57 recent-onset RA patients (88%) and in 40 (70%) of the same 57 patients 3 years later (p<0.0001 for both comparisons).
Eleven of 51 (22%) patients with RA of long duration, 19/43 (44%) patients with SLE and 16/19 (84%) patients with pSS, but none of 20 patients with MS, had elevated anti-PAD levels.
The arginine-citrulline converting enzyme PAD was recognized as a new antigen against which patients with inflammatory rheumatic diseases frequently show IgG class antibodies.