Background/Purpose:

Anti-cyclic citrullinated peptide (CCP) antibodies in juvenile idiopathic arthritis (JIA) have been identified as an important indicator for destructive disease, as is the case with rheumatoid arthritis (RA). Recently, studies have focused on identifying the target proteins of the citrulline modification in both RA and JIA. We found that both IgG anti-citrullinated fibrinogen and α-enolase antibodies were present in our JIA population. In this study, we evaluated serum from patients with various subtypes of JIA to further investigate the presence of isotypes (IgA, IgM) of anti-citrullinated fibrinogen and anti-citrullinated α-enolase, and their association with rheumatoid factor (RF) and anti-CCP antibody isotypes (IgA, IgM, IgG) and other clinical parameters.

Methods:

Sera were obtained from 93 JIA patients, 17 systemic lupus erythematosus (SLE) patients, and 10 healthy children. All sera were measured for antibodies against citrullinated and native fibrinogen and α-enolase IgA and IgM by ELISA. Results were compared to anti-CCP antibody isotypes and RF isotypes, in addition to previously measured IgG anti-citrullinated fibrinogen and α-enolase antibodies. All results were also correlated with various clinical parameters.

Results: 

IgA anti-citrullinated α-enolase antibodies were positive in 14, IgG in 9, and IgM in 11 JIA patients. IgA anti-citrullinated fibrinogen antibodies were positive in 16, IgG in 31, and IgM in 17 JIA patients. Overall, the isotypes of anti-citrullinated fibrinogen and α-enolase appeared more frequently in the polyarticular subset of JIA. One IgM RF-positive polyarticular JIA patient was positive for all 3 isotypes of anti-citrullinated fibrinogen antibodies. IgM anti-citrullinated α-enolase antibodies correlated significantly with IgM anti-citrullinated fibrinogen antibodies (r=0.479, p<0.001), and IgM anti-citrullinated α-enolase antibodies correlated significantly with IgM anti-CCP antibodies (p<0.005). IgM anti-citrullinated fibrinogen antibodies correlated significantly with erythrocyte sedimentation rate (p<0.05). IgA anti-citrullinated α-enolase antibodies correlated significantly with IgA anti-citrullinated fibrinogen antibodies (p<0.05). IgA anti-citrullinated α-enolase antibodies also correlated significantly with IgA RF and IgM RF (p<0.05), and IgA anti-citrullinated fibrinogen antibodies correlated significantly with IgA anti-CCP antibodies and IgM RF (p<0.05). No significant differences were noted the levels of citrullinated autoantibody isotypes when comparing patients with and without joint damage.

Conclusion:

Studies have suggested measuring anti-CCP antibody isotypes in both RA and JIA patients, and recent studies have identified target proteins of the citrulline modification. We found that isotypes of both anti-citrullinated fibrinogen and α-enolase antibodies are present in the serum of JIA patients. JIA patients with elevated isotypes of anti-citrullinated fibrinogen and α-enolase antibodies should be evaluated prospectively in comparison with JIA patients who exhibit a less diverse isotype pattern to further determine their role in the pathogenesis of JIA.

---

« Back to 2012 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/measurement-and-evaluation-of-isotypes-of-anti-citrullinated-fibrinogen-and-anti-citrullinated-alpha-enolase-antibodies-in-juvenile-idiopathic-arthritis-patients/