(a,b and d) H8 CML mice were either left untreated (Ø, n=7) or treated with 5 × 106 MACS-purified IFNγ–competent (p14, n=7) or –deficient (p14xIFNγ−/−, n=3) effector CTLs 17 days after CML induction. Two days later, PD-L1 expression in lin−BCR-ABL1-GFP+ BM CMPs (c-kithiCD127−CD34+FcγR−), GMPs (c-kithiCD127−CD34+FcγR+), MPP2s (c-kithiCD135−CD48+CD150−), MPP1s (c-kithiCD135−CD48+CD150+), ST-LSCs (c-kithiCD135−CD48−CD150−) and LT-LSCs (c-kithiCD135−CD48−CD150+) was determined by FACS. (a) Representative FACS plot of PD-L1 expression on ST- and LT-LSCs from untreated or p14-treated H8 CML mice. (b) Fold change of MFIs of PD-L1 on LSC subsets versus no treatment (n=3–7 mice per group). Dotted line represents untreated H8 CML mice. (c) IFNγRα chain on CML progenitors (lin−c-kit+Sca-1−) and LSCs (lin−c-kithiSca-1+) of n=6 mice is shown. (d) Primary H8 CML mice were treated with p14 CTLs as described in a starting 17 days after transplantation. Two days later the expression of indicated inhibitory markers on CD8+ T cells in the BM was analyzed. Values represent the fold change in MFI versus untreated controls (n=4–5 mice per group). (e) Spleen weights and numbers of (f) CMPs, (g) GMPs and (h) LSCs were determined in lin−BCR-ABL1-GFP+ BM of H8 CML mice treated with rat-IgG (Veh, 200 μg intraperitoneally every third day), 3 × 106 FACS-purified p14 effector CTLs (p14), PD-1-deficient p14 effector CTLs (p14xPD-1−/−), anti-PD-1 mAb (αPD-1, 200 μg intraperitoneally every third day, clone: RMP1–14) alone or in combination with effector p14 T cells (αPD-1/p14) starting 17 days after CML induction. (i) Equal numbers of lin− cells were plated in methylcellulose and BCR-ABL1-GFP+ colonies were enumerated 7 days later by inverted fluorescence microscopy. (j) 5 × 106 BM cells from H8 CML mice were transplanted into lethally irradiated (2 × 6.5 Gy) recipient mice and survival was monitored. Pooled data from two independent experiments with n=6–9 mice per group are shown. (k) Kaplan–Meier survival curves of H8 CML mice treated as described in e–h. Pooled data from two independent experiments with n=4–7 mice per group are shown. (l) Frequency of BCR-ABL1-GFP+ granulocytes in peripheral blood and (m) BCR-ABL1-GFP+ colonies in lin− BM from H8 CML mice that were alive 90 days after CML induction. (n) Survival of lethally irradiated (2 × 6.5 Gy) secondary recipients that were injected with 1 × 107 BM cells from surviving αPD-1/p14- and p14xPD-1−/−-treated primary CML mice (n=4–6 mice per group). (k, n) Numbers of mice that succumbed to CML of total transplanted mice are indicated. Data are displayed as mean±s.e.m. Statistics: (c) Student’s t-test, (e– i) one-way analysis of variance, (j and k) log-rank test. *P<0.05, **P<0.01, ***P<0.001.