IDO1 and melanoma: GrB+ lymphocytes associated positively with PD-L1+ tumor and stromal immune cells (p-values 0.009 and 0.027, respectively) (Table 6), IDO+ melanoma cells (p < 0.001), and tumor nest CD68+ and CD163+ macrophages (p-values 0.002 and 0.003, respectively) (data not shown).