Calcium-dependent (C-type) lectins are a family of lectins which share structural homology in their high-affinity carbohydrate-binding domain. Proteins of the CLEC superfamily function in a variety of biological processes, inclusing cell adhesion, cell-cell signalling, glycoprotein turnover, apoptosis, inflammation, and immune response to pathogens. CLEC4K/Langerin is a type II membrane-associated receptor expressed exclusively by Langerhans cells, in astrocytoma, malignant ependymoma, but not in normal brain tissues. It recognizes mannose residues, induces membrane superimposition and zippering leading to formation of Birbeck granules. Defects in CLEC4K cause Birbeck granule deficiency, a condition characterized by the absence of Birbeck granules in epidermal Langerhans cells.