CTRL and graft versus host disease: To determine whether hPBMCs were still able to reduce leukaemia cells when PTCy combined with TOC is given as a treatment for GVHD, engraftment of THP‐1 leukaemia cells and human leukocytes in the liver (Figure 7) and spleen (Supplementary figure 5) of hPBMC only, Ctrl Ab, PTCy + TOC, hPBMC + Ctrl Ab and hPBMC + PTCy + TOC mice was assessed by flow cytometry using the above gating strategy (Figure 2a).