Initial work from our laboratory demonstrated MDSCs and TAMs constitute greater than 90% of the CD200R+ cells in the microenvironment of cutaneous squamous cell carcinoma (cSCC) and that production of critical microenvironment cues by these tumor-infiltrating myeloid lineages, including GM-CSF and G-CSF, was dependent on engagement of the Cd200-Cd200r axis [39]. This evidence concerns the gene CD200R1 and skin squamous cell carcinoma.