PDCD1 and neoplasm: Of note, in contrast to knocking out PD-1 in CAR-T cells, combining CAR-T cell therapy with anti-PD-1 antibody therapy could restore the activity of not only the infused CAR-T cells but also other innate immune cells, including tumor-infiltrating lymphocytes, in the tumor microenvironment and may provide more effects to eradicate cancer cells.