CLEC2D

CLEC2D, commonly known as LLT1 or OCIL, is the natural ligand of the NK-cell receptor CD161 (NKR-P1A). This type II transmembrane C-type lectin is expressed on dendritic cells, activated B cells, and some tumor cells, where it dampens NK-cell cytotoxicity and IFN-γ release through inhibitory CD161 signaling. Structurally related to the NKG2 family, LLT1 has been studied in viral infection, autoimmune disease, and tumor immune evasion, and blocking antibodies show promise for enhancing antitumor immunity. Within this receptor family it is distinctive for functioning mainly as a ligand for a lymphoid receptor rather than as a pathogen sensor. Recombinant CLEC2D is used to dissect CD161-mediated immune checkpoints.