BCR signalling regulates B-cell development and function. Coupling of the BCR with PKCβ results in up-regulated MAPK and NF-κB signalling, leading to apoptotic resistance. In addition, PKCβ has been shown to deactivate the non-receptor tyrosine kinase Btk, by phosphorylating Ser¹⁸⁰ and disrupting plasma membrane targeting. The PI3K-dependent PKCδ is activated by Syk, a tyrosine kinase proximal to the BCR. PKCδ activation is associated with elevated prosurvival signalling such as Notch2 and stabilization of anti-apoptotic factors such as Mcl-1 and XIAP. Ag, antigen; BLNK, B-cell linker; ERK, extracellular-signal-regulated kinase; GRB2L, Grb2 (growth-factor-receptor-bound protein 2)-like; IKK, inhibitor of NF-κB kinase; MEK, MAPK/ERK kinase; PLC, phospholipase C.