CD74
（重定向自Invariant chain）
![](/Images/godic/202501/20/Protein_CD74_PDB_1icf4730.png")
![](/Images/godic/202501/20/PBB_GE_CD74_209619_at_tn4730.png")
![](/Images/godic/202501/20/PDB_1icf_EBI4731.jpg")
![](/Images/godic/202501/20/PDB_1iie_EBI4731.jpg")
HLA class II histocompatibility antigen gamma chain also known as HLA-DR antigens-associated invariant chain or CD74 (Cluster of Differentiation 74), is a protein that in humans is encoded by the CD74 gene. The invariant chain (Abbreviated Ii) is a polypeptide involved in the formation and transport of MHC class II protein. The cell surface form of the invariant chain is known as CD74.