It would be of particular interest to investigate the role of PD-1-expressing T cells in CLL, given the potential for treating multiple myeloma by targeting PD-1 (Atanackovic et al., 2014) and the promising clinical response of solid tumours to anti-PD-1 treatment (Topalian et al., 2012). Here, PDCD1 is linked to B-cell chronic lymphocytic leukemia.