One example is IFN-γ signaling (resulting primarily from activation of Th1 cells), which was recently found to be crucial for maintaining beneficial immunity and proper brain functioning (e.g., clearance of misfolded proteins, modulation of neurotoxic inflammation, release of neurotrophic factors, and social performance) during aging and the progression of Alzheimer’s disease (9, 15, 21, 28, 29, 44). This evidence concerns the gene IFNG and early-onset autosomal dominant Alzheimer disease.