GCA and Alzheimer disease: To determine which circulating immune cells contributed to the increased GCA level, we further leveraged a single‐cell RNA sequencing dataset (GSE181279) that have analyzed circulating immune cells in healthy and AD patients.[12] Notably, we found that GCA was most abundantly expressed in macrophages (Figure 1C; Figure S1A, Supporting Information), which was consistent with our previous results.[11] The expression of GCA was even higher in macrophages from AD patients than in healthy individuals (Figure 1C).