Non-receptor tyrosine kinase indispensable for B lymphocyte development, differentiation and signaling.Binding of antigen to the B-cell antigen receptor (BCR) triggers signaling that ultimately leads to B-cell activation.After BCR engagement and activation at the plasma membrane, phosphorylates PLCG2 at several sites, igniting the downstream signaling pathway through calcium mobilization, followed by activation of the protein kinase C (PKC) family members.