Objectives. - Induction of antinuclear antibodies (ANA) has been reported in patients taking infliximab to treat refractory spondyloarthropathy, without concomitant methotrexate therapy. We investigated antibody induction in patients with spondyloarthropathy treated with both infliximab and methotrexate.

Methods. - In 33 patients meeting ESSG criteria for spondyloarthropathy, infliximab was given (infusions at weeks 0, 2, 6, 14, 22, and 30) in combination with methotrexate (10-25 mg/week). At baseline, 6 and 30 weeks after treatment initiation, the patients underwent indirect immunofluorescence testing for ANA and ELISAs for antibodies to double-stranded DNA, soluble nuclear antigens, and histones.

Results. - As compared to baseline, significant increases were found at week 30 in the number of patients with ANA (4% vs. 29%, P = 0.02), IgG antihistone antibodies (7% vs. 29%, P = 0.04), and IgM antihistone antibodies (29% vs. 57%, P = 0.03). No significant increases were noted for antibodies to double-stranded DNA or to soluble nuclear antigens. No cases of clinical lupus syndrome were recorded.

Conclusion. - Autoantibody induction was far less common in our patients than in the population studied by De Rycke et al. [Arthritis Rheum. 48 (2003) 1015], who found ANA in 88.6% and antibodies to double-stranded DNA in 17.1% of 35 patients taking infliximab without methotrexate. Methotrexate may reduce the risk of autoantibody induction and disimmunity associated with infliximab therapy.