Lysosome-associated membrane protein 5 (LAMP5), also known as BAD-LAMP, UNC-43, and C20orf103, is a new member of LAMP family. It is a transmembrane glycosylated protein localized in the ER-Golgi intermediate compartment (ERGIC). LAMP5 shares sequence and structural homology with the canonical LAMP1 (CD107a) and LAMP2 (CD107b) molecules, harbors an endosomal addressing signal within its cytoplasmic tail, and contains several conserved cysteine residues that allow for the formation of particular structural loops known as LAMP folds. In mice, LAMP5 is expressed in postnatal cortical neurons of particular layers, where it is enriched in defined zones along neuronal projections. Human LAMP5, like its murine homolog, is principally expressed in brain; it is also specifically found in primary CD303 (BDCA-2)-positive pDCs (plasmacytoid dendritic cells). It represents a novel marker of human primary and transformed pDCs.