Mouse CD301, also known as macrophage galactose-type C-type lectin, has two homologue genes, CD301a (MGL1) and CD301b (MGL2), while there is only one MGL in human and rat. Mouse CD301a and CD301b are ∼42 kD type II transmembrane glycoproteins containing a cytoplasmic domain, a transmembrane domain, a neck domain, and a carbohydrate recognition domain (CRD) within each molecule. CD301a is mainly expressed on a subset of macrophages and immature dendritic cells (DCs). CD301b is mainly found on conventional DCs. Although CD301a and CD301b share high amino acid sequence homology (92% for the intact sequence and 80% for the CRD), they display different carbohydrate specificities. CD301a was found to be highly specific for Lewis X and Lewis A structures, whereas CD301b, more similar to the human MGL, recognizes N-actetylgalactosamine (GalNAc) and galactose, including the O-linked Tn-antigen, TF-antigen, and core 2. So far, CD301a has been reported to be involved in recognition and endocytosis of glycoproteins with terminal Gal/GalNAc moieties. This contributes to defense against tumor cell metastasis, tissue remodeling, and clearance of apoptotic cells in embryos. CD301b is involved in the internalization of soluble polyacrylamide polymers (PAA) with alpha-GalNAc residues (GalNAc-PAA) in bone marrow derived dendritic cells.