Fig. 2

Brain aging entails IFN-I activation in microglia and other cell types a, Schematic showing IFN-inducible reporter model based on spontaneous Mx1-Cre-driven recombination in the ROSA26^mT/mG reporter line. b, Representative images of Mx1-GFP⁺ cells appearing throughout the lifespan in the hippocampus. 3 months, n = 4 animals; 5 months, n = 4 animals; 10 months, n = 2 animals; 17 months, n = 4 animals; 24 months, n = 12 animals. Scale bar, 100 μm. c, Representative images of Mx1-GFP⁺Iba1⁺ microglia in gray matter (hippocampus and cortex) and white matter (corpus callosum) of 24-month-old animals (representative of n = 12 animals). Scale bar, 50 μm. Quantification of GFP⁺ percentages of all microglia by age and brain region (hippocampus, n = 3,650 cells across ages; cortex, n = 3,133 cells across ages; corpus callosum, n = 1,641 cells across ages. 3 months, n = 4 animals; 5 months, n = 4 animals; 10 months, n = 2 animals; 17 months, n = 4 animals; 24 months, n = 12 animals). Frequencies of GFP⁺ and GFP⁻ microglia were analyzed by chi-squared tests, and P values indicate comparisons of each time point with 3 months as a reference time point for each region. d, Examples of diverse, but less frequent, Mx1-GFP⁺ cell types observed in 24-month-old brains, including GFAP⁺ astrocytes, CC1⁺ oligodendrocytes (arrowheads), NeuN⁺ neurons, and blood vessels. Representative of n = 12 animals. Scale bars, 50 μm. See Fig. S2 for additional quantification