Fig. 1.

IDO positive tumors show increased infiltration of CSF-1R expressing MDSCs. (a) B16-IDO and B16-WT tumors and spleens were harvested 2 weeks after tumor cell inoculation and analyzed for infiltration with MDSC subsets. Results are shown for total myeloid cells (CD11b⁺) as frequencies of CD45⁺ cells. (b) Frequencies of CD11b⁺ Gr1^high and CD11b⁺ Gr1^int subsets of total CD45⁺ TILs and CD45⁺ splenocytes. (c) In vitro suppressive activity of tumor-infiltrating CD11b⁺ Gr1^int cells purified from B16-IDO tumor-bearing mice. Percent CD8⁺ T cell proliferation (left panel) and representative histograms of CD8⁺ T cell proliferation in CD11b⁺ to CD8⁺ T cell ratio of 1:1 (right panel). (d) Long-term survival of anti-CTLA-4 + PD-1 treated B16-IDO and B16-WT tumor-bearing mice. (e) Expression of CSF-1R in Gr1^int and Gr1^high cells within the CD11b⁺ gated population of TILs and splenocytes of B16-IDO tumor-bearing mice. Data depicted are mean ± SEM from 3 independent experiments with 5–10 mice/group.