CD4 and neoplasm: We found that after TDO2 inhibition, in the proximal region from the tumor nests (<20 μm), the proportions of Tregs (Foxp3+CD4+) in CD4+ T cells and exhausted CD8+ T cells (TIM-3+CD8+) in CD8+ T cells were significantly reduced (P < 0.05, Figure 8, I–L).