Detection of autoantibodies to the 65-kD isoform of glutamate decarboxylase by radioimmunoassay.
Autoantibodies (AAb) to glutamate decarboxylase (GAD) occur with a high prevalence in sera of newly diagnosed type I (insulin-dependent) diabetic patients. The aim of this study was to establish a GAD-AAb radioimmunoassay using 125I-labelled GAD65 and to evaluate this assay in a cross-sectional study with newly diagnosed type I diabetic patients (diabetes duration < 6 weeks). Furthermore, subjects at high risk of developing type I diabetes and individuals suffering from other autoimmune diseases were examined in this assay. For GAD-AAb detection, 125I-labelled GAD65 was incubated with 10 microliters of human serum overnight on ice. Thirty of 51 (59%) type I diabetic patients but none of the 54 healthy blood donors tested were found to be positive. A displacement step using 100,000 g supernatant from rat brain containing or not containing GAD showed the specificity of the binding of 125I-GAD65. Concerning the individuals at high risk of developing diabetes. 9/12 (75%) islet cell antibody (ICA)-positive non-diabetic and 4/34 (12%) ICA-negative subjects with metabolic abnormalities were GAD-AAb positive. These results show the association between type I (insulin-dependent) diabetes mellitus and the occurrence of GAD65-AAb, which possibly predicts a risk of developing the disease.
Lühder
F
F
Gerhardt Katsch Institute of Diabetes Research, University of Greifswald, Germany.
Woltanski
K P
KP
Mauch
L
L
Haubruck
H
H
Kohnert
K D
KD
Rjasanowski
I
I
Michaelis
D
D
Ziegler
M
M
D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000201:enzymology / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology / Q000276:immunology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D011863:Radioimmunoassay; D011994:Recombinant Proteins / Q000276:immunology; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D011994:Recombinant Proteins; D005968:Glutamate Decarboxylase