A 10-year-old boy was diagnosed with a recent onset of diabetes mellitus and requires daily insulin therapy. Injury to pancreatic islet cells in this patient was most likely mediated by which of the following mechanisms of disease?

The patient is a case of type 1 diabetes mellitus (T1DM) T1DM is an autoimmune disease in which islet destruction is caused primarily by immune effector cells reacting against endogenous b-cell antigens. Cell-mediated immune mechanisms are fundamental to the pathogenesis of type 1 diabetes mellitus (T1DM), and cytotoxic T lymphocytes sensitized to b-cells in T1DM persist indefinitely. Circulating antibodies (choice A) against components of the b-cells of the islets, including insulin itself, are identified in most newly diagnosed patients with diabetes. However, these antibodies are regarded as a response to b-cell injury, rather than the initial cause of b-cell depletion. Evidence for viral causes of diabetes mellitus type 1 (choice C) remains controversial.