IL15 and B-cell chronic lymphocytic leukemia: At first, we evaluated the BPs direct cytotoxicity on leukemic B cells obtained ex-vivo from peripheral blood of CLL patients, either resting (as they are derived from the periphery) or stimulated in vitro by classical microenvironment-mimicking stimuli (CD40L + IL4, activating the CD40 pathway, or CpG + IL15, engaging the Toll-Like Receptor 9) [27].