Rat CD172a, also known as a signal-regulatory protein alpha (SIRPalpha), is a 75-110 kD transmembrane glycoprotein involved in the receptor tyrosine kinase coupled signaling pathway. It belongs to the Ig superfamily primarily expressed on monocytes/macrophages, granulocytes, dendritic cells and neurons. CD172a serves as a substrate of activated receptor ttyrosine kinases (RTKs). The interaction of the CD172a intracellular domain with SHP-1 and SHP-2 displays negative signaling in the regulation of leukocyte adhesion and transmigration, T cell activation, macrophage fusion and phagocytosis. CD47 (IAP) is an extracellular ligand for CD172a.