Infliximab, but not etanercept, induces IgM anti-double-stranded DNA autoantibodies as main antinuclear reactivity : biologic and clinical implications in autoimmune arthritis

Objective. To analyze the clinical and biologic correlates of autoantibody induction during longer-term tumor necrosis factor alpha (TNF alpha) blockade with either the monoclonal antibody infliximab or the soluble receptor etanercept. Methods. Thirty-four patients with spondylarthropathy (SpA) and 59 patients with rheumatoid arthritis (RA) were treated with infliximab for 2 years. Additionally, 20 patients with SpA were treated with etanercept for 1 year. Sera were blindly analyzed for antinuclear antibodies (ANAs), anti-double-stranded DNA (anti-dsDNA) antibodies, anti-extractable nuclear antigen (anti-ENA) antibodies, and antihistone, antinucleosome, and anticardiolipin antibodies (aCL). The anti-dsDNA antibodies were isotyped. Results. High numbers of infliximab-treated patients with SpA or RA had newly induced ANAs (61.8% and 40.7%, respectively) and anti-dsDNA antibodies (70.6% and 49.2%, respectively) after I year, but no further increase between year I and year 2 was observed. In contrast, induction of ANAs and anti-dsDNA antibodies was observed only occasionally in the etanercept-treated patients with SpA (10% of patients each). Iso-typing revealed almost exclusively IgM or IgM/IgA anti-dsDNA antibodies, which disappeared upon interruption of treatment. Neither infliximab nor etanercept induced other lupus-related reactivities such as anti-ENA antibodies, antihistone antibodies, or antinucleosome antibodies, and no clinically relevant lupus-like symptoms were observed. Similarly, infliximab but not etanercept selectively increased IgM but not IgG aCL titers. Conclusion. The prominent ANA and anti-dsDNA autoantibody response is not a pure class effect of TNF alpha blockers, is largely restricted to short-term IgM responses, and is not associated with other serologic or clinical signs of lupus. Similar findings with aCL suggest that modulation of humoral immunity may be a more general feature of infliximab treatment