Of note, the PD-1+ expression levels of the input samples were low (13.0-36.3% of CD4+; 3.1-14.7% of CD8+) but fell within the broad range reported for CLL PBMCs, which spans and encompasses the healthy donor range (Brusa et al., 2013; Gassner et al., 2014; Nunes et al., 2012; Riches et al., 2013; te Raa et al., 2014). This evidence concerns the gene PDCD1 and B-cell chronic lymphocytic leukemia.