PDCD1 and B-cell chronic lymphocytic leukemia: While there was no differences in PD-1 mRNA levels in CLL cells in both groups (2−ΔΔCt of 0.637 vs. 0.326, p = 0.34, Figure 3C), the ΔMFI of PD-1 was higher in the group who up-regulated CD38 after stimulation (ΔMFI of 6.240 vs. −6.670, p = 0.0093, Figure 3D).