Rheumatoid Arthritis Research Today is a free monthly online journal that collates and summarizes the latest research about Rheumatoid Arthritis, including details on treatment, symptoms, causes, medication.

Serum IgG antibodies to peptidylarginine deiminase 4 in rheumatoid arthritis and associations with disease severity.

Halvorsen EH, Pollmann S, Gilboe IM, van der Heijde D, Landewé R, Ødegård S, Kvien TK, Molberg Ø

Institute of Immunology, University of Oslo, Rikshospitalet University Hospital, 0027 Oslo, Norway. eirikhha@medisin.uio.no

BACKGROUND: Antibodies targeting citrullinated antigens are specific for rheumatoid arthritis (RA). Citrullination is catalysed by the peptidylarginine deiminase (PAD) enzyme family. Critical enzymes are often targeted by disease-specific antibodies in complex immune-mediated diseases. Here, we have tested for autoantibodies against human recombinant PAD4 (hPAD4) in Caucasian RA patients. METHODS: A time-resolved fluorometric immunoassay based on hPAD4 was developed to analyse sera from two RA cohorts (n = 237 and n = 177), one systemic lupus erythaematosus (SLE) cohort (n = 84) and 148 healthy controls. Simple and multiple analyses were performed to examine possible associations between anti-hPAD4 and disease variables. RESULTS: Raised levels of anti-hPAD4 IgG were found in both RA cohorts compared to the controls, and 23% of the RA patients were anti-hPAD4 IgG positive. Anti-hPAD4 was associated with anti-cyclic citrullinated peptide (CCP) and rheumatoid factor (RF), as well as increased physical disability. Anti-hPAD4 was also associated with higher longitudinal radiographic damage scores and increased clinical joint pathology, but weaker than anti-CCP. No associations were found between anti-hPAD4 and selected Human leukocyte antigen (HLA)-DRB1 variants. CONCLUSIONS: Approximately 23% of Caucasian RA patients have serum IgG antibodies against hPAD4.The presence of serum anti-hPAD4 IgG was in simple analyses associated with a more severe disease phenotype, and the association with physical disability was maintained in multiple analyses.

Published 22 February 2008 in Ann Rheum Dis, 67(3): 414-7.
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