BTLA expression was significantly increased on leukemic cells from patients with CLL compared to their healthy counterpart [mean fluorescence intensity (MFI) ± standard error of mean (SEM): 30,363.3 ± 1593 vs. 21,905 ± 1394, p < 0.0001] (Figure 1A,B). This evidence concerns the gene BTLA and B-cell chronic lymphocytic leukemia.