CLEC4D (C-type lectin domain family 4 member D), also known as CLCSF8, CLEC-6, and MCL, is a 30kD type II transmembrane (TM) glycoprotein that belongs to the CLR (C-type Lectin Receptor) family of molecules. It is synthesized as a 215 amino acid (aa) protein that contains a 17 aa N-terminal cytoplasmic domain, a 21 aa TM segment, and a 177 aa C-terminal extracellular region. The extracellular region shows a short stalk and a 118 aa CRD (carbohydrate recognition domain). The nature of its carbohydrate ligand is unknown. CLEC4D is restricted to monocytes/macrophages and serves as an endocytic receptor. Homodimers and homotrimers form on the cell surface. The human CLEC4D extracellular region shares 63% aa sequence identity with the mouse extracellular region.