Analysis of the GAD65-GAD65 autoantibody interaction.
BACKGROUND
GAD(65)Ab are important markers of risk of development of type 1 DM.


METHODS
With the need to improve the disease specificity of GAD(65)Ab measurement in mind, we have analysed the interaction between recombinant human GAD(65) and GAD(65)Ab from different groups of subjects in terms of association and dissociation rate constants and equilibrium constants. In addition, binding of GAD(65)Ab from various groups of subjects to wild-type GAD(65) versus GAD(65) containing a mutation E517P was studied.


RESULTS
Affinity constants for serum GAD(65)Ab in 12 type 1 DM patients ranged from 0.9 x 10(10) L/mol to 11.2 x 10(10) L/mol and from 0.8 x 10(10) L/mol to 14.0 x 10(10) L/mol in sera from 11 individuals without type 1 DM. Serum GAD(65)Ab concentrations assessed by Scatchard analysis ranged from 0.04 to 24.8 microg/mL in type 1 DM patients (n=12) and from 0.04 to 141.8 microg/mL in individuals without type 1 DM (n=11).


CONCLUSIONS
Overall, our study indicated that GAD(65)Ab in different patients studied showed similar association and dissociation rate constants and similar affinity constants. However, GAD(65)Ab concentrations vary widely between different sera. There was a modest reduction of the median binding of GAD(65)Ab to GAD(65) E517P in the group of patients with type 1 DM compared to patients without type 1 DM.
Coco
Graziella
G
FIRS Laboratories, RSR Ltd., Parc Ty Glas, Llanishen, Cardiff, UK.
Chen
Shu
S
Powell
Michael
M
Brooking
Helen
H
Zanchetta
Renato
R
Betterle
Corrado
C
Smith
Bernard Rees
BR
Furmaniak
Jadwiga
J
D000293:Adolescent; D000328:Adult; D000915:Antibody Affinity; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis* / Q000201:enzymology / Q000276:immunology; D005260:Female; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011994:Recombinant Proteins / Q000276:immunology
D001323:Autoantibodies; D011994:Recombinant Proteins; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2