Autoantibodies to DEK oncoprotein in human inflammatory disease

Objective To evaluate the specificity of anti‐DEK antibodies for juvenile rheumatoid arthritis (JRA). Methods Anti‐DEK autoantibodies were measured by enzyme‐linked immunosorbent assay (ELISA) using affinity‐purified his6‐DEK fusion protein. Sera from 639 subjects (417 patients with systemic autoimmune disease, 13 with sarcoidosis, 44 with pulmonary tuberculosis, 125 with uveitis, and 6 with scleritis, and 34 healthy control subjects) were screened. Reactivity was verified by immunoblotting and immunoprecipitation studies using baculovirus‐expressed human DEK. Results Anti‐DEK activity was found at the following frequencies: JRA 39.4% (n = 71), systemic lupus erythematosus (SLE) 25.1% (n = 216), sarcoidosis 46.2% (n = 13), rheumatoid arthritis 15.5% (n = 71), systemic sclerosis 36.0% (n = 22), polymyositis 6.2% (n = 16), and adult Still's disease 0% (n = 21). Autoantibodies also were detected in 9.1% of tuberculosis sera (n = 44), but were undetectable in sera from the 34 healthy controls. Western blot and immunoprecipitation assay results correlated well with the ELISA findings. In general, levels of anti‐DEK autoantibodies were higher in SLE than in other patient subsets, including JRA. Conclusion Anti‐DEK autoantibodies are less specific for JRA than previously believed. They are produced in association with a variety of inflammatory conditions, many of which are associated with granuloma formation and/or predominant Th1 cytokine production. Anti‐DEK antibodies may be a marker for a subset of autoimmunity associated with interferon‐γ production rather than a particular disease subset.