Insulin-dependent diabetes mellitus (IDDM) results from a T-cell-mediated destruction of the insulin-producing β-cells. In this study, we designed a sensitive assay to detect and identify islet cell-reactive T-cells in patients with newly diagnosed IDDM. The relation between T-cell recognition of β-cell antigens with IDDM and the pathogenesis of the disease (the β-cell destruction process) was tested in a large group of IDDM patients and compared with T-cell responses in nondiabetic children with other chronic inflammations and in immunologically normal, age-matched control subjects. The results demonstrate that peripheral blood T-cells reacting with a β-cell membrane preparation enriched for insulin-secretory granule antigen were detectable in the majority of newly diagnosed IDDM patients (27 of 40 [67%]; mean stimulation index [SI] 37.0). Such reactivity was reduced postonset in IDDM patients proportionally to the duration of the disease (11 of 30 [37%]; mean SI 8.7). Nondiabetic age-matched control subjects showed no responses or moderate responses to the granule preparation (4 of 48 [8%]; mean SI 3.4). The magnitude of the T-cell response was significantly greater in newly diagnosed IDDM patients than in IDDM patients tested at least 2 years postonset (P < 0.001). Two children in remission for insulin dependency (so-called honeymoon period) displayed exceptionally high proliferative responses to insulin-secretory granules (mean SI 86.7). These results imply that T-cell recognition of insulin-secretory granule antigens is associated with IDDM and in particular with the immune-mediated process of β-cell destruction.

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