PDCD1 and neoplasm: To determine whether PD-1 deficient monocytes had the ability to develop trained immunity and lasting antitumor protection, CD45+CD11b+Ly6ChiLy6G− monocytes isolated from the bone marrow of Pdcd1fl/flLysMCre or Pdcd1f/f mice on day 9 post injection with MC17-51 tumor cells, when tumors had comparable size between the two groups, were mixed with an equal number of MC17-51 tumor cells and injected subcutaneously into naïve WT mice.