To further verify the aging-associated change in the cell ratio, we performed single-cell analysis at the protein level. Similar to the cell clusters and subsets in scRNA-seq results, in CyTOF analysis, we identified 21 sub-clusters with nine subsets of TCs (CD4 Naive, CD4 Tcm, CD4 Tem, CD4 Treg, CD8 Naive, CD8 Tem, CD8 CTL, CD4+ CD8+, CD4− CD8−), three subsets of NKs (CD56bright NK1, CD16+CD57− NK2 and CD16+CD57+ NK3), four subsets of BCs (Naive BC, Memory BC, ASCs, and ABCs), three subsets of MCs (CD14high MCs, CD16high MCs and intermediate MCs), and two subsets of DCs (pDCs and cDCs) (Fig. S4A–K, see Table S3B for the details).