CD28 and neoplasm: Tumor-derived CD11b+Gr-1− e-MDSCs suppressed T cells more potently, which was demonstrated by the significant higher inhibition of the anti-CD3/CD28 McAb-stimulated T cell proliferation (15.10 ± 2.50 vs. 23.90 ± 1.48 vs. 46.50 ± 3.34% P = 0.0017, P = 0.0386, Figure 4D), and induced more apoptotic T cells (26.90 ± 0.87 vs. 20.03 ± 0.97 vs. 3.33 ± 0.30%, P < 0.001, P = 0.0063, Figure 4E) when compared with the CD11b+Gr-1+ MDSCs or normal controls.