PDCD1 and neoplasm: In view of the reshaped tumor immune microenvironment, such as the enrichment of CD8+ T cells, the downregulation of the immunosuppressive cells, the upregulated PD-L1 expression (Supplementary Fig. 35), and the enhanced tumor accumulation and penetration of anti-PD-1 antibody by Met@Man-MPs, the effects of Met@Man-MPs on the anticancer activity of anti-PD-1 antibody were first evaluated in H22 tumor-bearing mice (Fig. 8a–i).