PDCD1 and neoplasm: The combination of SPN@Pro-Gem with PD-1 antibody resulted in further improvements in tumor suppression and, more importantly, in increased levels of T cells during immunotherapy: a decrease in the number of MDSCs in the blood (Fig. 6L); and an effective increase in the number of CD4+ T cells and CD8+ T cells in the tumor (Fig. 6M and N).