PD-1 and PD-L expression in H8-cpCML and H8-bcCML mice. (A) PD-1 expression on purified p14 CD8⁺ T cells (CD45.1⁺CD8⁺Va2⁺) isolated from the spleen 5 days after transfer. One representative histogram from 3 to 5 mice per group is shown. One representative experiment of 2 is shown. (B) CTLA-4 expression on purified p14 CD8⁺ T cells (CD45.1⁺CD8⁺Vα2⁺) isolated from the spleen 7 days after transfer. (C) cpCML and bcCML were generated from C57BL/6 donors in p14 recipient mice. PD-1 expression on total CD8⁺ T cells and on unspecific CD8⁺ T cells (Vα2⁺) in the spleen was analyzed 20 days after bone marrow transplantation. One representative FACS plot of 3 is shown. (D) PD-L1 and PD-L2 expression in the spleen and bone marrow of H8-cpCML, H8-bcCML, and naive C57BL/6 mice. Cells were gated on GFP-positive granulocytes (CML) and granulocytes (naive C57BL/6) in the forward/side scatter. Shaded area, isotype control H8-cpCML or H8-bcCML; thin line, isotype control naive C57BL/6. One representative experiment of 3 is shown. (E) Purified p14 CD8⁺ T cells or p14 × PD-1^−/− CD8⁺ T cells were restimulated in vitro with granulocytes from H8-cpCML, H8-bcCML, or H8 mice. ³H-thymidine incorporation is shown as proliferation index (mean ± SEM of 3 mice per group).