CD6 is a type I transmembrane glycoprotein that belongs to the scavenger receptor cysteine-rich superfamily (PMID: 21880988). It is composed of an extracellular region, which consists of three tandem SRCR domains, a transmembrane region, and a cytoplasmic tail devoid of intrinsic catalytic activity but harboring several phosphorylatable residues suitable for intracellular signal transduction (PMID: 38139340; 23711376). CD6 is expressed by T cells, medullary thymocytes, a subset of B cells and NK cells, and in some cells of the brain (PMID: 1919444; 21178331). CD6 plays a role in lymphocyte activation, proliferation, and survival processes via interaction with its endogenous ligands.