CD274 and B-cell chronic lymphocytic leukemia: PD-L1, which is upregulated at the surface of CLL cells (Ramsay et al., 2012; Grzywnowicz et al., 2015), interacts with its receptor PD-1 whose expression, transiently enhanced during the physiological activation processes, is aberrantly upregulated on effector T cells in the stromal CLL niche (Riches et al., 2013), thus potentiating the PD1/PD-L1 signaling axis.