S100A9 and Alzheimer disease: A total of 70391 sorted cells from 15 MCI/AD and 44 normal CSF samples were grouped into 12 clusters, and seven cell types were finally annotated, including T cells (n=55435) identified by the expression of CD3D, B cells (n=224), marked by MS4A1, DC (n=9749) which expressed the HLA-DRA, ILC (n=2406) marked by KLRD1, pDC (n=738) identified by LILRA4, macrophages (n=354) which were positive for C1QB, monocytes (n=1485) defined by their classical marker S100A9 (Figures 3A–C).