CD4 and B-cell chronic lymphocytic leukemia: In line with our previous report [11], we observed an induction of PD1 expression in CD4 as well as CD8 T cells in peripheral blood samples during disease development in CLL-transplanted congenic WT recipient mice (mean CD4: preTx 11.7%, postTx 23.2%, p = 0.0091, n = 14; mean CD8: preTx 3.6%, postTx 16.8%, p = 0.0002, n = 14) (Figure 1B,C).