Monocyte/Macrophage/DC is the largest cell population in PBMCs
Monocyte/Macrophage/DC (Cluster 0, 4, 6, and 8) accounted for 50.7% (15186 cells), highest proportion of all cell types. After unsupervised clustering, six cell subgroups (M0–5) (Figure 2a) were identified from the Monocyte/Macrophage/DC population. M0 and M1 subgroups were found to highly express S100A8, S100A9, and S100A12, implying their role in antigen recognition and signal transduction, thus they were classified as classic CD14+ monocytes(20, 21) (Figure 2b, c) . Other evidence in M1 came from the highly expressed genes of chemokines and cytokines such as CXCL8, CCL3, IL1B, and CXCL2(20, 21) (Figure 2c) . M2 subgroup was found to express HES1, HES4, and ATF3 genes associated with regulation of transcription(22, 23) and were classified as non-classic CD16+ monocytes. M3 constituted fewer genes, mainly TAOK1, LINC01681, and SPATA22 with unspecified roles and requires further exploration. The significantly higher expression of FCGR3A(CD16) in M4 subgroup (Figure 2c) along with expression of IFN-related genes IFITM2 and IFITM3 suggests that M4 has genes with similar roles, as were found in subgroup M2 and were classified as CD16+ monocytes(20, 21) . M5 subgroup consisted of genes involved in HLA-type recognition genes and were classified as CD1C+ DC(21, 24) (Figure 2c) .