PDCD1 and B-cell chronic lymphocytic leukemia: Of note, while PD-1 expression was significantly higher in CD45RA−CXCR5+ Tfh from patients with CLL compared to HC, CD45RA−CXCR5+ Tfr, which were significantly increased among Treg in patients (Figure 3F), displayed significantly lower PD-1 expression compared to HC (Supplementary Figure S2A–C).