T cell response pattern to glutamic acid decarboxylase 65 (GAD65) peptides of newly diagnosed type 1 diabetic patients sharing susceptible HLA haplotypes.
Autoantibodies and autoreactive T lymphocytes directed against several pancreatic beta cell proteins such as GAD65 have been identified in the circulation before and at the onset of clinical type 1 (insulin-dependent) diabetes. Using GAD65 synthetic peptides, we studied the proliferative response of peripheral blood mononuclear cells (PBMC) either from recently diagnosed type 1 diabetic patients, of whom the majority share the disease-associated HLA class II haplotype (DR4-DQB1*0201 or DR3-DQB1*0302), or from HLA-matched control subjects. We found that 67% (14/21) of the type 1 diabetic patients and 39% (9/23) of the control subjects exhibited a positive proliferative response. Compared with control subjects, however, PBMC from diabetic patients proliferated more frequently (P < 0.05) in the presence of peptide pools from the C-terminal region of GAD65 (amino acids 379-585). Diabetic patients with the same HLA-DQ or HLA-DR alleles showed partially identical T cell reactivity, but no clear correlation could be made between MHC class II specificity and T cell epitopes because of multiple combinations of class II alleles. In addition, by flow cytometry, we studied the direct binding of GAD65 peptides to MHC class II molecules of Epstein-Barr virus (EBV)-transformed B (EBV-B) cells obtained from a diabetic patient. We found that 11 GAD peptides were able to bind to the highly susceptible haplotype DRB1*0301/0401-DQA1*0301/0501-DQB1*0302/0201 on the surface of EBV-B cells in partial correlation with the results obtained in the proliferation assays.
Rharbaoui
F
F
CNRS-UMR9921, Faculté de Pharmacie, Montpellier, France.
Mayer
A
A
Granier
C
C
Bouanani
M
M
Thivolet
C
C
Pau
B
B
Orgiazzi
J
J
Madec
A M
AM
D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D001323:Autoantibodies / Q000276:immunology; D001324:Autoantigens / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology / Q000821:virology; D002455:Cell Division; D002461:Cell Line, Transformed; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics / Q000276:immunology*; D005260:Female; D020022:Genetic Predisposition to Disease; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006680:HLA Antigens / Q000235:genetics / Q000276:immunology*; D006239:Haplotypes / Q000235:genetics / Q000276:immunology; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D007223:Infant; D007515:Islets of Langerhans / Q000201:enzymology / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology; D020033:Protein Isoforms / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
D001323:Autoantibodies; D001324:Autoantigens; D006680:HLA Antigens; D010446:Peptide Fragments; D020033:Protein Isoforms; D005968:Glutamate Decarboxylase