CD161: Proteins and Enzymes

CD161, also known as KLRB1, NK1.1, and NKR-P1A is a 40 kDa type II transmembrane glycoprotein that contains one C-type lectin domain in its extracellular region. CD161 is expressed as a disulfide-linked dimer on the surface of Th17 cells and NK cells as well as on subsets of CD1-restricted T cells, intestinal NT cells, peripheral memory T cells, monocytes, and dendritic cells. It binds to OCIL/CLEC2d, leading to an inhibition of NK cell-mediated cytotoxicity and IFN-gamma secretion. Alternatively, CD161 can enhance TCR activation to CD1d ligation. CD161+ cell populations are depleted in ulcerative colitis, Grave's disease, and AIDS, although CD161+ T cells are activated during asthmatic attacks. Additional related proteins are expressed in mouse but not human: the inhibitory NKR-P1B and D, and the stimulatory NKR-P1A, C, and F.