E, F. In vitro T cell suppression activity of CT26-tumor infiltrating CD11b+ myeloid cells collected at 2 weeks post-treatment with vehicle or 75 mg/kg TP-16. CD8+ T cells were labeled with CFSE and then stimulated with CD3/CD28 antibodies for 3 days in the absence or presence of tumor-infiltrating CD11b+ myeloid cells from vehicle- or 75 mg/kg TP-16-treated CT26 tumors. Representative flow cytometry histograms (E) and percentages (F) of proliferating CD8+ T cells when plated in a ratio of 2:1, 1:1, and 1:2 CD8+ T cells to CD11b+ myeloid cells (n = 3). 