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) .