STAT1 and Alzheimer disease: While various heterozygous STAT1 mutations were described to be associated with impaired IFNγ responses (49, 66), an intriguing aspect of AD STAT1 heterozygous dominant MSMD is the apparent partial preservation of IFNα/IFNβ responses and lack of broad susceptibility to viruses, as might have been expected, given the central position of STAT1 downstream of the type I IFN receptor (29, 67, 68) (Figure 3).