401. Demonstration of GAD-65 as the main immunogenic isoform of glutamate decarboxylase in type 1 diabetes and determination of autoantibodies using a radioligand produced by eukaryotic expression
- Author
-
Olle Kämpe, F A Karlsson, Christer Betsholtz, L Christmanson, Licio A. Velloso, and Anders Hallberg
- Subjects
Adult ,Male ,endocrine system ,endocrine system diseases ,Adolescent ,Glutamate decarboxylase ,Immunoblotting ,Immunofluorescence ,Kidney ,Transfection ,Epitope ,law.invention ,Cell Line ,Islets of Langerhans ,Antigen ,law ,Reference Values ,Chlorocebus aethiops ,medicine ,Animals ,Humans ,Cloning, Molecular ,Child ,Aged ,Autoantibodies ,geography ,geography.geographical_feature_category ,medicine.diagnostic_test ,biology ,Glutamate Decarboxylase ,Autoantibody ,nutritional and metabolic diseases ,General Medicine ,DNA ,Middle Aged ,Islet ,Molecular biology ,Rats ,Isoenzymes ,Molecular Weight ,Diabetes Mellitus, Type 1 ,Immunology ,Recombinant DNA ,biology.protein ,Electrophoresis, Polyacrylamide Gel ,Female ,Antibody ,Research Article - Abstract
Plasmids containing cDNA for the rat 67- and 65-kD isoforms of glutamate decarboxylase (GAD-67 and GAD-65) were expressed in COS-cells, and lysates of [35S]methionine-labeled cells were used for immunoprecipitations. Sera from 38 patients with type 1 (insulin-dependent) diabetes mellitus, which precipitated a 64-kD antigen from rat islets, reacted with recombinant GAD-65 in relation to their anti-64-kD titers. The eight strongest sera also precipitated recombinant GAD-67, suggesting that certain epitopes are common to both isoforms. Subsequently, [35S]methionine-labeled GAD-65 was purified from COS cell lysates and employed in a binding assay with 50 sera of patients with recent onset of type 1 diabetes mellitus. 38 sera (76%) precipitated labeled GAD-65 with titers that correlated with islet cell antibodies (ICA), determined in a standard immunofluorescence assay. 2 sera were GAD positive but ICA negative, 4 were positive only for ICA, and 6 were negative for both GAD and ICA, as were the sera of 20 controls. The data illustrate that antibodies against GAD-65 are present in a majority of patients with type 1 diabetes mellitus and that autoantibodies against other islet cell antigens also exist. The radioligand-binding assay, which is convenient and sensitive for detecting GAD antibodies, will facilitate the screening of individuals with autoimmune islet cell disease.
- Published
- 1993