Heterogeneity of Ly6G+Ly6C+ myeloid-derived suppressor cell (MDSC) infiltrates during S. aureus biofilm infection

The two immune cell populations Myeloid-derived suppressor cells (MDSCs), monocytes (MONO) and neutrophils (PMNs) are difficult to differentiate because of shared surface marker expression. Here we utilize the integrin receptor CD11b combined with conventional Ly6G and Ly6C expression to more accurately separate cellular populations via FACS. Then we apply high-throughput RNA Sequencing to Ly6G+Ly6C+CD11bhigh MDSC, Ly6G+Ly6C+CD11blow PMN and Ly6G-Ly6C+ monocyte populations. A total of 6,466 genes were significantly differentially expressed in MDSCs vs. monocytes, whereas only 297 genes were significantly different between MDSCs and PMNs. A number of genes implicated in cell cycle regulation were identified, and in vivo EdU labeling revealed that over 75% of MDSCs proliferated locally at the site of S. aureus biofilm infection. RNA-Seq of myeloid-derived suppressor cells (MDSCs), neutrophils (PMNs), and monocytes during S. aureus biofilm infection in mice