PDCD1 and neoplasm: Notably, immunofluorescence staining of NK1.1 showed that there was no significant change in infiltration of NK cells before and after treatment with anti–PD-1 plus anti–CTLA-4 in MC38 tumors (Supplemental Figure 10, A and B), which further confirmed that the changes in tumor uptake of 68Ga-grazytracer after ICI therapy was related to the secretion of granzyme B by CD8+ T cells.