– Signal regulatory protein α (SIRPα) is a regulatory membrane glycoprotein from SIRP family expressed mainly by myeloid cells and also by stem cells or neurons.SIRPα acts as inhibitory receptor and interacts with a broadly expressed transmembrane protein CD47 also called the “don´t eat me” signal.Cancer cells highly expressed CD47 that activate SIRP α and inhibit macrophage-mediated destruction. SIRP alpha V5 Protein, Human, Recombinant (His & Avi), Biotinylated is expressed in HEK293 mammalian cells with C-His-Avi tag. The predicted molecular weight is 40 kDa and the accession number is P78324 variant 5.