Autoantibody to scaffold attachment factor B (SAFB): A novel connective tissue disease-related autoantibody associated with interstitial lung disease.

OBJECTIVE: To identify and characterize a novel connective tissue disease (CTD)-related autoantibody (autoAb) directed against scaffold attachment factor B (SAFB). METHODS: AutoAb specificity was analyzed using RNA and protein-immunoprecipitation assays. Autoimmune targets were affinity purified using patients' sera and subjected to liquid chromatography mass spectrometry. RESULTS: By immunoprecipitation assay, 10 sera reacted with a protein with a molecular weight of approximately 160 kDa. Liquid chromatography mass spectrometry of the partially purified autoantigen and additional immunoblot-based analyses revealed that the Ab specifically recognized SAFB. Anti-SAFB Abs were detected in 2 of 646 patients with systemic sclerosis (SSc) (0.3%), 1 of 1570 patients with polymyositis/dermatomyositis (0.06%), 4 of 270 patients with interstitial lung disease (ILD) (1.5%), 1 of 43 patients with overlap syndrome (2.3%) and 2 patients with other diseases including primary Raynaud's disease and eosinophilic pneumonia. Five patients with anti-SAFB Abs had Raynaud's phenomenon and 3 had nail fold punctate hemorrhage. Of note, 8 of the 10 patients (80%) suffered from ILD. None of the patients with anti-SAFB Abs had pulmonary arterial hypertension, heart disease, or renal involvement. CONCLUSIONS: Anti-SAFB Ab is a novel CTD-related autoAb possibly associated with ILD.

Myositis-specific anti-155/140 autoantibodies target transcription intermediary factor 1 family proteins.

OBJECTIVE: To identify the 140-kd autoantigen recognized by anti-155/140 autoantibodies that are associated with adult cancer-associated dermatomyositis (DM) and juvenile DM and to determine the clinical relevance of anti-155/140 antibodies in a large cohort. METHODS: Sera from 456 DM patients were assessed for the presence of anti-155/140 antibodies by immunoprecipitation using K562 cell extracts as substrate. Using immunoprecipitation and Western blotting, we then examined whether anti-155/140-positive sera recognized transcription intermediary factor 1α (TIF-1α), TIF-1ß, and TIF-1γ. The clinical associations of antigen reactivity were also evaluated. RESULTS: Anti-155/140-positive sera reacted with 140-kd TIF-1α in addition to 155-kd TIF-1γ. Among sera from 456 DM patients, 52 were reactive with both TIF-1α and TIF-1γ, while another 25 were reactive with TIF-1γ alone. Additionally, 7 were reactive with TIF-1ß. Malignancy was more frequently found in adult patients with both anti-TIF-1α and anti-TIF-1γ antibodies than in those with anti-TIF-1γ antibodies alone (73% versus 50%; P < 0.05). In addition to juvenile DM patients and middle-aged and older DM patients with high percentages of malignancy, 8 "young adult" DM patients without malignancy had these autoantibodies. CONCLUSION: Anti-155/140 antibodies target TIF-1 family proteins, TIF-1α and TIF-1ß, in addition to TIF-1γ. Since TIF-1 proteins have significant roles in oncogenesis, these antibodies may be produced during misdirected antitumor immunity.

Clinical correlations with dermatomyositis-specific autoantibodies in adult Japanese patients with dermatomyositis: a multicenter cross-sectional study.

OBJECTIVE: To clarify the association of clinical and prognostic features with dermatomyositis (DM)-specific autoantibodies (Abs) in adult Japanese patients with DM. DESIGN: Retrospective study. SETTING: Kanazawa University Graduate School of Medical Science Department of Dermatology and collaborating medical centers. Patients A total of 376 consecutive adult Japanese patients with DM who visited our hospital or collaborating medical centers between 2003 and 2008. MAIN OUTCOME MEASURES: Clinical and laboratory characteristics of adult Japanese patients with DM and DM-specific Abs that include Abs against Mi-2, 155/140, and CADM-140. RESULTS: In patients with DM, anti-Mi-2, anti-155/140, and anti-CADM-140 were detected in 9 (2%), 25 (7%), and 43 (11%), respectively. These DM-specific Abs were mutually exclusive and were detected in none of 34 patients with polymyositis, 326 with systemic sclerosis, and 97 with systemic lupus erythematosus. Anti-Mi-2 was associated with classical DM without interstitial lung disease or malignancy, whereas anti-155/140 was associated with malignancy. Patients with anti-CADM-140 frequently had clinically amyopathic DM and rapidly progressive interstitial lung disease. Cumulative survival rates were more favorable in patients with anti-Mi-2 compared with those with anti-155/140 or anti-CADM-140 (P < .01 for both comparisons). Nearly all deaths occurred within 1 year after diagnosis in patients with anti-CADM-140. Conclusion Dermatomyositis-specific Abs define clinically distinct subsets and are useful for predicting clinical outcomes in patients with DM.