OBJECTIVE—Although most patients with type 1 diabetes are considered to have T-cell–mediated autoimmune disease, a method of measuring of pancreatic β-cell–specific T-cell function in cases of type 1 diabetes has yet to be established. Here, we focused on interferon-inducible protein-10 (IP-10), a chemokine that promotes the migration of activated T-helper 1 (Th1) cells and measured serum IP-10 levels in patients with human type 1 diabetes, which is regarded as a Th1-mediated disease.
RESEARCH DESIGN AND METHODS—Serum samples were obtained from diabetic patients, and the levels of autoantibodies (GAD and insulinoma-associated protein-2 [IA-2]) and IP-10 were measured. Diabetic patients positive for either or both of the autoantibodies were classified as Ab+ type 1, and those negative for both were classified as Ab− type 1. To evaluate islet antigen–specific responses, peripheral blood from patients stimulated with or without GAD was used, and intracellular cytokine staining for flowcytometry was performed.
RESULTS—The Ab+ and Ab− type 1 groups both showed a significantly higher serum IP-10 level than the healthy subjects (P < 0.001 and P < 0.05, respectively), and the IP-10 level in the recent-onset Ab+ subgroup was significantly higher than that in the established (longstanding) Ab+ subgroup (P < 0.002). Furthermore, there was a significant positive correlation between the serum IP-10 level and the number of GAD-reactive γ-interferon–producing CD4+ cells in the Ab+ type 1 group (P < 0.007).
CONCLUSIONS—Our findings demonstrate that measurement of serum IP-10 concentrations is useful in patients with type 1 diabetes.
It is well known that lymphocytic infiltration of pancreatic islets, a condition referred to as "insulitis," is seen in acute-onset type 1 diabetes at autopsy and in biopsy specimens. However, there have been no proven cases of insulitis in type 1 diabetes with residual beta-cell function. We believe that this is the first type 1 diabetic patient with residual beta-cell function who was proven to have T-cell insulitis. This novel evidence will contribute to the proper classification and treatment of diabetes and to a better understanding of the pathophysiology of type 1 diabetes.
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