CD160, also known as BY55, is a 27 kD glycoprotein and member of the Ig superfamily. It is anchored to the cell membrane through glycosylphosphatidylinositol (GPI) and forms disulfide-linked multimers. A soluble form of CD160 is secreted by activated CD8+ T cells. Expressed by NK, NKT, gamma/delta T cells, intestinal intraepithelial T cells and a subset of memory CD8+ T cells, CD160 binds both classical and non-classical MHC class I molecules. It is also a ligand for HVEM. CD160 enhances proliferation of activated CD8+ T cells and triggers cell cytotoxicity in NK cells.