CD9 and Alzheimer disease: During AD progression, microglia gradually switched from a homeostatic state to DAM, as evidenced by specific markers (e.g., Csf1, Itgax, Cd63, Ank, Axl, Igf1, Clec7a, Tyrobp, Ctsb, Ctsd, Ctsl, Cd9, Ctsz, Ccl6, Trem2, Spp1, Lpl, Cst7, Apoe).