CLEC2D (C-type lectin domain family 2 member D), also known as LLT1 (lectin-like transcript 1) or OCIL (Osteoclast inhibitory lectin), is a single-pass type II membrane protein expressed by hematopoietic cells and osteoblasts (PMID: 21930700; 14753741). Its expression was found to be tightly correlated with activation on T cells, NK cells, B cells, and DCs (PMID: 21930700). CLEC2D is a ligand for the human NKR-P1A (CD161) receptor and that their interaction differentially regulates NK- and T-cell functions (PMID: 16339513, 16339512). It inhibits the formation and function of osteoclasts and modulates the release of interferon-gamma by human NK cells (PMID:14753741; 20415786).