CD28 and melanoma: To mimic the tumor microenvironment, B16-F10 melanoma cells and primary CD8+ T cells isolated from splenocytes were stimulated with interferon-gamma (IFN-γ) or anti-CD3/CD28 antibodies, and remarkable upregulation of PDL1 and PD1 was observed in B16-F10 cells and CD8+ T cells, respectively (Supplementary Fig. 7).