According to published data [1, 6, 8–10, 33–35], we observed an accumulation of PD-1-expressing CD4+ T cells in blood samples of patients with CLL or DLBCL in comparison to healthy controls (HC) (Supplementary Fig. 1A–E), and subsequently aimed to characterize these cells. Here, PDCD1 is linked to B-cell chronic lymphocytic leukemia.