C-type lectin (CLEC) family is a type of carbohydrate-binding protein domain named lectin. C-type lectins are the most diverse and prevalent lectin family in immunity with its requirement for calcium for binding. Proteins including a C-type lectin domain have diverse range of functions including cell-cell adhesion, immune response to pathogens and apoptosis. There are at least 14 types of C-type lectins: typeⅠto typeⅩⅣ. CLEC4D(CLECSF8) is a typeⅡ membrane glycoprotein belonging to the C-type lectin family, with restricted expression in the monocyte/macrophage lineage. It plays important roles in the function of macrophages.