PDCD1 and B-cell chronic lymphocytic leukemia: Building on these findings, a comparative analysis of CD8+ T-cells of paired blood and lymph node samples of CLL patients showed an accumulation of PD-1+ CD8+ T-cells harboring all key features of exhaustion in lymph nodes but not blood samples, namely the expression of several inhibitory receptors and reduced cytokine production (Fig. 3) [25, 49].