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-1β, 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-1β. 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-1β, in addition to TIF-1γ. Since TIF-1 proteins have significant roles in oncogenesis, these antibodies may be produced during misdirected antitumor immunity.