Cambier et al. show that the tyrosine phosphatase SHP-1 and the inositol phosphatase SHIP-1 are required to maintain B cell anergy.

, via SH2 binding, and activation of Lyn. Upon dual phosphorylation, ITAMs become docking sites for the kinase Syk that, in turn, is activated by phosphorylation, leading to phosphorylation of several downstream targets and culminating in B cell activation (Packard and Cambier, 2013). Whereas Lyn plays a role in B cell activation, it also propagates activity of regulatory signaling pathways by, for example, phosphor-