Abnormal morphology of cerebral microvascular casts of IFN^High mice demonstrated by scanning electron microscopy. (A-C) Scanning electron micrograph of cerebral microvascular casts of wild-type mice at low (×25), medium (×80), and high power (×300). (D-F) Transgenic type I IFN production: Abnormal microvascular morphology in IFN^High mice, with variations in microvessel caliber (red arrows), ectatic vessels, and microaneurysms (blue arrows). Such microvascular abnormalities were observed in all IFN^High mice with highest levels of brain-restricted IFN-α1 production (n = 6) but not in WT mice.