Korean Diabetes Journal 1999;23(3):269-277.
Published online January 1, 2001.
Measurement of Anti-Phogrin Antibody in Korean Autoimmune Deabetes; Comparison to Anti-IA-2 Antibody.
Moon kyu Lee, Yong Ki Min, Myung Shik Lee, Sung Hoon Kim, Byoung Joon Kim, Dong Jun Kim, Jong Ryeal Hahm, Dong Kyu Jin, Kyoung Ah Kim, Kwang Won Kim
1Division of Endocrinology & Metabolism, Samsung Medical Center, SungKyunKwan University School of Medicine, Seoul, Korea.
2Department of Medicine and Pediatrics, Samsung Medical Center, SungKyunKwan University School of Medicine, Seoul, Korea.
Since the discovery of IA-2 as a major autoantigen in type 1 diabetes, the question arose as to whether other PTPs (protein tyrosine phosphatases) could act as diabetic autoantigens as well. A novel PTP, designated IA-2 B (phogrin; phosphatase homologue in granules of insulinoma) was isolated that has a high sequence similarity to IA-2. Since some studies suggested that auto- immunity to phogrin, rather than IA-2 may be more closely associated with the development of type 1 diabetes, we measured the frequency of anti-phogrin antibody in Korean patients with type 1 diabetes and compared it with that of anti-IA-2 antibody/ anti-GAD antibody. METHODS: The anti-phogrin antibody and the anti-IA-2 antibody were measured by radioligand binding assays using in vitro transcribed and translated S-labeled phogrin and IA-2, respectively. Anti-GAD antibody was measured using a commercial radioimmunoassay kit (RSR, Cardiff, U.K.). The subjects in this study consisted of 41 patients with classical type 1 diabetes, 22 with slowly progressive type 1 diabetes, and 39 with type 2 diabetes. Their average mean age was 16.9 years, 37.9 years and 45.3 years respectively. RESULTS: The prevalence of anti-phogrin antibody, anti-IA-2 antibody and anti-GAD antibody in classical type 1 diabetes was 24.4%, 26.8% and 51.2% respectively. That, in slowly progressive type 1 diabetes was 0%, 9.1% and 40.9% respectively. When the anti-GAD antibody assay and the anti-IA-2 antibody assay were combined, the prevalence of autoantibodies was 58.5% in classical type 1 diabetes and 50% in slowly progressive type I diabetes. However, the addition of the anti-phogrin antibody to the anti-GAD antibody/anti-IA-2 antibody measurement did not significantly increase the prevalence of autoantibody. The level of the antiphogrin antibody was positively correlated with that of the anti-IA-2 antibody. The presence of the anti-phogrin antibody and the anti-IA-2 antibody was negatively correlated with the age at diagnosis. One patient with type 1 diabetes had the anti-phogrin antibody without the anti-IA-2 antibody. CONCLUSION: Combined measurement of the anti-phogrin antibody with the anti-IA-2 antibody/ anti-GAD antibody did not significantly increase the prevalence of autoantibodies in Korean patients with type 1 diabetes. In the majority of Korean type 1 diabetes patients, the anti-phogrin antibody appears to share epitopes with the anti-IA-2 antibody. However, a small proportion of type 1 diabetes patients may have a specific autoimmune response to phogrin.
Key Words: Key words, Autoimmune diabetes, Anti-phogrin antibody, Anti-IA-2 antibody, Anti- GAD antibody

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