KLRK1 and neoplasm: Among them, the typical are PD-1/PD-L1 (Shi et al., 2021), CTLA-4 (Chen W. et al., 2023), NKG2D (Wang et al., 2020), TLRs (Behzadi et al., 2021), TGF-β (Gulley et al., 2022), etc. For example, antiprogrammed cell death receptor ligand 1 (aPD-L1) released by the hydrogel inhibited the PD-1/PD-L1 pathway and restored cytotoxic T cell killing function at the tumor site (Shi et al., 2021).