Fig. 2.

Tumor microenvironment induces PD-1 expression on MDSCs. Bone marrow cells were obtained from the femurs of Balb/c mice, and then CD11b⁺ cells were sorted. (A, B) The CD11b⁺ cells were cultured in fresh medium in the presence of 10 ng/ml GM-CSF, in the absence or presence of IL-6 or TCCM. The cells were collected on day 4 for cell analysis. (C, D) The CD11b⁺ cells were cultured in fresh medium in the presence of 10 ng/ml GM-CSF, in the absence or presence of indicated concentrations of TCCM. The cells were collected at 24 h and 96 h for cell analysis. (E, F) BM-MDSCs were co-cultured with 4T1 tumor cells (ratio of 10:1). After 96 h, non-adherent cells were collected for cell analysis. All experiments were independently repeated at least 3 times and a representative figure was shown in (A), (C), and (E). ^**p<0.01, ^***p<0.001.