BTK and chronic graft versus host disease: A clinically-relevant example is the specific targeting of BCR-induced NF-κB signalling (see Figure 1D) in B-cells using inhibitors of Burton tyrosine kinase (BTK), such as Ibrutinib, which is approved for the treatment of refractory mantle cell lymphoma (MCL) [228] and marginal zone lymphoma (MZL) [229], chronic lymphomatic leukemia (CLL) [230], small lymphocytic lymphoma (SLL) [230], Waldenström’s macroglobulinemia [231] and chronic graft versus host disease [232] The highly-restricted pattern of BTK expression to B cells means that Ibrutinib has a generally well-tolerated safety profile.