IFN-γ is required for diabetes in GM-CSF/IL-3–deficient mice. (A) Fasting blood sugar levels were determined for IFN-γ–deficient (n = 8) and GM-CSF/IL-3/IFN-γ–deficient (n = 10) mice and compared with GM-CSF/IL-3–deficient mice shown in Figure 2. GM-CSF/IL-3/IFN-γ–deficient animals showed significantly reduced fasting blood sugar levels compared with GM-CSF/IL-3–deficient mice (P < .001). (B) Glucose tolerance tests were performed on GM-CSF/IL-3/IFN-γ–deficient mice (n = 6). Peak glucose levels were significantly reduced compared with GM-CSF/IL-3–deficient animals shown in Figure 3 (P < .001). (C) Absence of insulitis in a GM-CSF/IL-3/IFN-γ–deficient mouse, original magnification ×200. (D) Islet cell adenomas in GM-CSF/IL-3/IFN-γ–deficient mouse, original magnification ×200. (E). Insulin (red) and somatostatin (brown) staining in adenoma in GM-CSF/IL-3/IFN-γ–deficient mouse, original magnification ×400.