In support of this notion, adoptively transferred CD8+ cells purified from spleens of OT-1 mice that express a CLL-irrelevant TCR in our model showed enhanced PD-1 expression in Eμ-TCL1 mice with overt leukemia compared to wild-type mice (Supplementary Fig. 4). This evidence concerns the gene CD8A and B-cell chronic lymphocytic leukemia.