Cell-mediated immunity was evaluated in patients with diabetes mellitus by delayed hypersensitivity skin tests and in vitro lymphocyte transformations. Only 44% of diabetic patients had skin test reactivity to Candida antigen, compared with 88% of normal controls (P < 0.001). Insulin-dependent diabetic (IDD) patients had abnormally low lymphocyte transformation responses to phytohemagglutinin, ...