CD4 and melanoma: Similarly, anti-CTLA-4 increased the expression of T cell activation marker PD-1 on both CD8+ (Fig. 2d) and CD4+ TILs (Supplementary Fig. 2e) and concurrently reduced CD73 expression, an immunosuppressive ectoenzyme that catalyzes immunostimulatory ATP to potent immunosuppressive adenosine19, only in scrambled control melanoma.