There are 2 qualitatively different signals from the B-cell receptor (BCR; a constitutive one, and one associated with antigen stimulation), both transduced by the tyrosine kinase syk, eventually resulting in a robust calcium response. BCR signaling can be inhibited by removing the antigen (eg, Helicobacter pylori), directly targeting the BCR (eg, anti-idiotype antibodies), or by inhibition of the critical mediator, syk (eg, with the tyrosine kinase inhibitor R406).