Enzyme-linked immunosorbent assays for detection of anti-transcriptional intermediary factor-1 gamma and anti-Mi-2 autoantibodies in dermatomyositis.
BACKGROUND
Autoantibodies against transcriptional intermediary factor 1 (TIF1) and Mi-2 are selectively detected in patients with dermatomyositis (DM). To measure these antibodies readily, the development of reliable ELISA systems has been needed.


OBJECTIVE
This study aimed to establish enzyme-linked immunosorbent assays (ELISAs) for anti-TIF1γ and anti-Mi-2β antibodies (Abs) and to assess their utility.


METHODS
Serum samples were obtained from 104 patients with classic DM, 68 with clinically amyopathic DM (CADM) and 70 with polymyositis, who were followed up at 8 medical centers across Japan. Serum samples from 190 patients with other connective tissue diseases (CTDs) and 123 healthy individuals were also assessed. Serum antibody levels were examined by ELISAs coated with full-length TIF1γ or Mi-2β proteins produced by a baculovirus expression system. To assess the cross-reactivity, partial-length Mi-2β proteins with or without mutations were produced and examined for reactivity.


RESULTS
When compared with immunoprecipitation assay, anti-TIF1γ Ab ELISA showed 100% sensitivity and 100% specificity, while anti-Mi-2β Ab ELISA showed 100% sensitivity and 99.6% specificity. Anti-TIF1γ Ab was positive in 30 (28.8%) with classic DM and 4 (5.9%) with CADM, whereas 14 (13.5%) with classic DM, but none with CADM, were positive for anti-Mi-2β Ab. Of 30 anti-TIF1γ Ab-positive DM patients, 23 (67.6%) had malignancy. Anti-Mi-2β Ab-positive serum samples exhibited modest cross-reactivity with the TIF1γ protein due to the homologous amino acid sequence containing cysteines in their plant homeodomains.


CONCLUSIONS
The current study demonstrates the utility of newly established ELISAs for anti-TIF1γ and anti-Mi-2β Abs, which can serve as easier detection systems for routine testing.
Department of Dermatology, School of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. Electronic address: mfujimoto@md.tsukuba.ac.jp.
Manabu
M
Fujimoto
Medical & Biological Laboratories Co., Ltd., 4-5-3 10F, Sakae, Naka-ku, Nagoya, Aichi 406-0008, Japan.
Akihiro
A
Murakami
Medical & Biological Laboratories Co., Ltd., 4-5-3 10F, Sakae, Naka-ku, Nagoya, Aichi 406-0008, Japan.
Shunsuke
S
Kurei
Department of Dermatology, School of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
Naoko
N
Okiyama
Unit of Translational Medicine, Department of Immunology and Rheumatology, Nagasaki University School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki City, Nagasaki 852-8501, Japan.
Atsushi
A
Kawakami
Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan.
Michiaki
M
Mishima
Division of Rheumatology, Department of Internal Medicine, Tokai University, School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.
Shinji
S
Sato
Department of Dermatology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu City, Gifu 501-1194, Japan.
Mariko
M
Seishima
Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi, Hamamatsu, Shizuoka 431-3192, Japan.
Takafumi
T
Suda
Department of Rheumatology and Clinical Immunology, Graduate School of Medicine, Kyoto University, Kyoto, Yoshida-Honmachi, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan.
Tsuneyo
T
Mimori
Department of Dermatology, School of Medicine, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa 920-8641, Japan.
Kazuhiko
K
Takehara
Department of Allergy and Rheumatology, Nippon Medical School Graduate School of Medicine, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.
Masataka
M
Kuwana
D000328:Adult; D000368:Aged; D001323:Autoantibodies; D003545:Cysteine / Q000737:chemistry; D003882:Dermatomyositis / Q000097:blood* / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011487:Protein Conformation; D000072417:Protein Domains; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014157:Transcription Factors / Q000276:immunology*
D001323:Autoantibodies; C045760:Mi-2 antibodies; C511956:TRIM33 protein, human; D014157:Transcription Factors; D003545:Cysteine
Autoantibody; Dermatomyositis; Enzyme-linked immunosorbent assay; Mi-2; Transcriptional intermediary factor 1