HLA‐DR3 mediated CD4 T cell response against GAD65 in type 1 diabetes patients

Abstract

Aim We planned this study to identify diabetogenic glutamic acid decarboxylase (GAD65) peptides possibly responsible for human leucocyte antigen (HLA)‐DR3/DQ2‐mediated activation of GAD65‐specific CD4 T cells in type 1 diabetes (T1D). Methods Top 30 GAD65 peptides, found to strongly bind in silico with HLA‐DR3/DQ2 molecules, were selected and grouped into four pools. The peptides were used to stimulate CD4 T cells of study subjects in 16‐h peripheral blood mononuclear cell culture. CD4 T cells' stimulation in terms of interferon‐gamma (IFN‐γ), interleukin (IL)‐17, tumor necrosis factor‐alpha (TNF‐α), and IL‐10 expression was analyzed using flow cytometry. Results Although all four GAD65 peptide pools (PP1‐4) resulted in significantly higher expression of IFN‐γ by CD4 T cells (p = .003, p < .0001, p = .026, and p = .002, respectively), only pool 2 showed significant increase in IL‐17 expression (p < .0001) in T1D patients vs healthy controls. Interpeptide group comparison for immunogenicity revealed significantly higher IFN‐γ and IL‐17 expressions and significantly lower IL‐10 expression for PP2 compared to other groups (p < .0001, p = .02, and p = .04, respectively) in patients but not in controls. Further, group 2 peptides resulted in significant increase in CD4 T cells' expression of IFN‐γ and IL‐17 (p = .002 for both) and significant decrease in IL‐10 (p = .04) in HLA‐DRB1*03‐DQA1*05‐DQB1*02+ patients vs HLA‐DRB1*03‐DQA1*05‐DQB1*02+ controls. The CD4 T cells' expression of IL‐17 was significantly higher (p = .03) in recently diagnosed vs long‐standing HLA‐DRB1*03‐DQA1*05‐DQB1*02+ T1D patients. Conclusion GAD65 peptides, particularly those belonging to PP2, induced CD4 T cells to express IFN‐γ and IL‐17 cytokines in T1D patients, suggesting that group 2 peptides possibly presented by HLA‐DR3 molecule to CD4 T cells shift immune balance toward inflammatory phenotype in patients.

Important denominator between autoimmune comorbidities: a review of class II HLA, autoimmune disease, and the gut

“…As previously discussed, the age of T1D diagnosis and type of autoantibody first observed are also strongly associated HLA haplotype; autoantibodies, IAA and IA2A, are associated with DR4-DQ8 and early seroconversion, but glutamic acid decarboxylase autoantibodies (GADA) are found in individuals have later seroconversion and are strongly associated with DR3-DQ2.5 ( 12 , 52 – 55 ). Recent evidence suggests that GAD peptides bind to DR3-DQ2.5 molecules and in turn induce CD4+ T cell cytokine expression ( 59 ). In addition to the cis DR3-DQ2.5/DR4-DQ8 heterodimer, the heterozygote DR3-DQ2.5/DR4-DQ8 in trans heterodimer form encoded by DQA1 *05:01- DQB1 *03:02 is also very high risk for T1D ( 9 ).…”

Presence of Type 1 Diabetes-Related Autoantibodies in Pediatric Population in Bosnia and Herzegovina

“…The combined measurement of these autoantibodies raised the detection rate of diabetes autoimmunity to 98% at the onset of the disease, which resulted in the recognition of these markers in routine diagnostics. The presence of GAD and IA-2 are associated with older age, and GAD additionally with female gender ( 7 ). Autoantibodies can appear very early in life, and the order of appearance is related to genotype ( 8 ).…”