(Ig)–like domains and whose cytoplasmic region contains immunoreceptor tyrosine-based inhibition motifs that mediate the binding and activation of the protein tyrosine phosphatases SHP-1 and SHP-2.(19,20) Tyrosine phosphorylation of SIRPα is triggered by various growth factors and cytokines as well as by integrin-mediated cell adhesion to extracellular matrix proteins.