Measurement and evaluation of isotypes of anti-citrullinated fibrinogen and anti-citrullinated alpha-enolase antibodies in juvenile idiopathic arthritis

Objective Our objective was to evaluate sera from juvenile idiopathic arthritis (JIA) patients to investigate the presence of isotypes (IgA, IgG, IgM) of anti-citrullinated fibrinogen and anti-alpha-enolase antibodies and their association with rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody isotypes. Methods Sera were obtained from 89 JIA patients and were measured for isotypes (IgA, IgM) of anti-citrullinated and native fibrinogen and anti-alpha-enolase antibodies by enzyme-linked immunosorbent assay. Results were compared to anti-CCP antibody isotypes and RF isotypes, in addition to previously measured IgG anti-citrullinated fibrinogen and alpha-enolase antibodies. Results IgA anti-citrullinated fibrinogen antibodies were positive in 20 JIA patients and IgM in 11 JIA patients. Two IgM RF-positive polyarthritis patients were positive for all 3 isotypes of anti-citrullinated fibrinogen antibodies. IgA anti-citrullinated alpha-enolase antibodies were positive in 7 JIA patients and IgM in 9 JIA patients. IgA and IgG anti-citrullinated fibrinogen antibodies were commonly found in JIA patients positive for IgG anti-CCP antibodies and IgM RF. IgG anti-CCP antibodies and IgM RF levels were significantly higher in JIA patients with 3 or more anti-citrullinated autoantibody isotypes present. Conclusion We have shown that isotypes of anti-citrullinated fibrinogen and alpha-enolase can be found in the serum of children with JIA of all onset types. Citrullinated autoantibody isotype diversity may indicate a more severe disease course in JIA patients.