Abstract

BACKGROUND
Type 1 diabetes mellitus is attributable to progressive autoimmune destruction of insulin-producing pancreatic islet cells, which result in absolute deficiency of insulin. Serum antibodies against islet antigens in patients with type 1 diabetes mellitus have been recognized. These include insulin autoantibodies, islet cell cytoplasmic antibodies(ICA) and glutamic acid decarboxylase(GAD) antibodies. Although, indirect immunofluorescence assay for measuring ICA have been studied as a marker for the loss of beta cell function and for monitoring the effects of immunosuppressive treatment at onset of type 1 diabetes mellitus, problem with reproducibility and standardization between laboratories still exist. Further, because the classic assays of glutamic acid decarboxylase(GAD) are still rather time-cansuming, a more simple and reproducible radioligand assay is widely used currently. Thus, this study was performed to evaluate the prevalence of cytoplasmic islet cell antibodies and glutamic acid decarboxylase antibodies in Korean patients with type 1 diabetes mellitus and to observe the associations of glutamic acid decarboxylase antibodies with islet cell cytoplasmic antibodies. METHODS: Patients with type 1 diabetes(n=26) and control(n=20) sera were used to develop quantitative antibody assays with in vitro synthesized recombinant S-methionine-labelled GAD, and protein A-sepharose to separate free from antibody-bound ligand. Also the sera were screened for conventional ICA-IgG by means of indirect immunotluorescence on section of blood group 0 human pancreas. Then, Positive sample were titered by doubling dilution. RESULTS: The overall prevalences of islet cell cytoplasmic antibodies and glutamic acid decarboxylase (GAD) antibodies in Korean patients with type 1 diabetes mellitus were 46%(12 of 26) and 39%(10 of 26) respectively. In a subset of these patients with recent onset type 1 diabetes mellitus(<1 year), the prevalence of islet cell cytoplasmic antibodies(ICA) and glutamic acid decarboxylase (GAD) antibodies were all 75%(3 of 4). The prevelances of islet cell cytoplasmic antibodies(ICA) and glutamic acid decarboxylase(GAD) antibodies were dereased in patients with long standing diabetes at 41%(9 of 22) and 32%(7 of 22) respectively. The frequency of glutamic acid decarboxylase(GAD) antibodies increased as the JDF units of islet cell cytoplasmic antibodies(ICA) increased. The frequency of islet cell cytoplasmic antibodies(ICA) increased as the GAD index increased. CONCLUSION: These results suggest that islet cell cytoplasmic antibodies(ICA) test by standard indirect immunofluorescence technique and glutamic acid decarboxylase(GAD) antibodies test by radioligand binding assay is useful for screening and diagnosis of Korean patient with type 1 diabetic children, But, long-term prospective studies on large cohorts of patients should be done to evaluate the predictive power and the prevalence of islet cell cytoplasmic antibodies and glutamic acid decarboxylase antibodies in Korean patients with type 1 diabetic children.

• Keywords: Type 1 diabetes;ICA;GAD antibody;Radioligand binding assay;