PDCD1 and neoplasm: Combined blockade of the IL33/ST2 and PD-1/PD-L1 pathways can promote the accumulation of CD4+ and CD8+ T lymphocytes [73], enhance the activity of NK cells, and have better anti-tumor efficacy than treatments that block the IL33/ST2 or PD-1/PD-L1 pathway alone (p < 0.05) [74], indicating that it is also a potential new approach for immunotherapy.