CD160 (also BY55) is a 27 kDa member of the immunoglobulin superfamily of molecules.  It is expressed on select hematopoietic cell types, including CD56 ^dim CD16 ⁺ cytotoxic NK cells, CD8 ⁺ CD28 ^- effector T cells, δ/ gamma T cells, and restricted CD4 ⁺ T cells.  It is a receptor for HLA-C molecules, and its engagement induces CD160 ⁺ NK cells to both secrete IFN-gamma plus TNF-alpha and initiate a cytotoxic program.  Human CD160 was originally identified as a 155 amino acid (aa) proprotein (aa 27‑181).  It contains a 132 aa mature region (aa 27-159) and a C-terminal prosegment that is cleaved to create a GPI linkage. The mature region possesses one V‑type Ig-like domain (aa 27-122).  CD160 is found as a soluble, disulfide-linked 80 kDa multimer (likely trimer) that is generated by proteolysis of the GPI-linked form. This 80 kDa form, plus others, are highly resistant to reduction. There is also a 100-110 kDa multimeric transmembrane (TM) form that is associated with activated NK cells. It contains a 55 aa substitution for Gly180-Leu181, and shows a 20 aa TM segment between aa 163-182.  The TM form appears to have a splice variant that lacks aa 25-133.  Over aa 27-159, human CD160 shares 62% aa identity with mouse CD160.