What precedes the initial tyrosine phosphorylation of the high affinity IgE receptor in antigen-activated mast cell?

An interaction of multivalent antigen with its IgE bound to the high-affinity IgE receptor (FcεRI) on the surface of mast cells or basophils initiates a series of signaling events leading to degranulation and release of inflammatory mediators. Earlier studies showed that the first biochemically defined step in this signaling cascade is tyrosine phosphorylation of the FcεRI β subunit by Src family kinase Lyn. However, the processes affecting this step remained elusive. In this review we critically evaluate three current models (transphosphorylation, lipid raft, and our preferential protein tyrosine kinase–protein tyrosine phosphatase interplay model) substantiating three different mechanisms of FcεRI phosphorylation.