CD206

CD206, also known as the mannose receptor C-type 1 (MRC1) or simply the mannose receptor, is a type I transmembrane protein in humans that belongs to the C-type lectin receptor family. It is predominantly expressed on macrophages and dendritic cells and plays a key role in carbohydrate recognition and endocytic uptake.

The extracellular portion of CD206 contains a C-type lectin domain that binds terminal mannose, fucose, and N-acetylglucosamine on glycoproteins and microbial surfaces. It also includes a fibronectin type II domain and a series of collagen-like repeats, forming a stalk that extends the carbohydrate-binding region away from the cell surface. The protein is linked to a transmembrane segment and a short cytoplasmic tail that contains endocytic motifs, enabling rapid internalization of bound ligands.

Functionally, CD206 mediates endocytosis and phagocytosis of ligands with mannose-terminated glycans, contributing to clearance of glycoproteins and to pathogen recognition. By delivering internalized material to endosomal/lysosomal compartments, it supports antigen processing and presentation, thereby influencing adaptive immune responses. The receptor also participates in tissue homeostasis through uptake and processing of glycoproteins.

Expression of CD206 is associated with alternatively activated (M2) macrophages and certain dendritic cell subsets. It can be upregulated by Th2-type cytokines such as IL-4 and IL-13. Due to its specific carbohydrate recognition and efficient endocytosis, CD206 is explored as a target for glycan-directed vaccine delivery and other therapeutic strategies.