GAD‐Reactive T Cells Were Mainly Detected in Autoimmune‐Related Type 1 Diabetic Patients with HLA DR9

A bstract : Type 1 diabetes mellitus (T1DM) is considered to be a T cell‐mediated disease, and many reports suggest that some HLA types, especially HLA DR4 and DR9, convey susceptibility to T1DM in Japanese. We investigated the association between T cell reactivity against GAD and HLA types in “islet‐associated autoantibody‐positive” T1DM in Japanese. Blood samples were obtained from 36 “autoantibody‐positive” type 1 diabetic patients with HLA DR4 or DR9 and 23 type 2 diabetic patients with HLA DR4 or DR9 as controls. They were divided into three groups, DR4/9, DR4/X, and DR9/X groups. In each HLA type group, GAD‐reactive IFN‐γ‐producing CD4 + cells were assessed by means of intracellular cytokine staining for flow cytometry. Type 1 diabetic patients with HLA DR9/X had significantly higher numbers of GAD‐reactive IFN‐γ‐producing CD4 + cells as compared to type 1 diabetic patients with DR4/X or DR4/9 ( P < 0.05 ) and all type 2 diabetic patients. There was no significant difference in the number of GAD‐reactive IFN‐γ‐producing CD4 + cells between type 1 diabetic and type 2 diabetic patients belonging to the DR4/X and DR4/9 groups. There was an association between T cell reactivity against GAD and HLA DR9 in Japanese type 1 diabetes.