PDCD1 and neoplasm: Silent signal-regulated protein α (SIRP-α) was found to counteract the effects of CD47, thereby activating inflammatory pathways in CAR-M cells and inducing M1 polarization, which exhibited significant anti-HER2+ tumor effects [55] Tumor-associated macrophages (TAMs) also express Programmed Cell Death Protein 1 (PD-1), which binds to its cognate ligand, PD-L1, expressed on tumor cells, thereby contributing to cancer progression.