Since ibrutinib, an inhibitor of Bruton’s tyrosine kinase (iBTK), effectively blocks BCR signaling in vitro (47) and in patients (48), we assessed the BTK dependency of autonomous signaling using TKO cells expressing CLL IgM BCRs (Figure 5, A and B). The gene discussed is CD40LG; the disease is B-cell chronic lymphocytic leukemia.