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?: (A) Antibody-mediated islet cell destruction, (B) Cell-mediated immunity, (C) Direct viral cytopathic effects, (D) Immune complex deposition
Answer is B. 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.