CD74

CD74, also known as the invariant chain that is associated with MHC class II molecules, is a non-polymorphic glycoprotein primarily expressed on antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells. It plays a crucial role in the synthesis and transport of MHC class II molecules, facilitating their movement from the endoplasmic reticulum to the cell surface. Within the endoplasmic reticulum, CD74 forms a trimeric complex with the α and β chains of MHC class II molecules, preventing premature binding of endogenous peptide fragments to MHC class II molecules intracellularly. Furthermore, CD74 participates in regulating immune responses by forming signalling complexes with molecules such as CD44 and CD91, thereby influencing cellular activation, proliferation, and inflammatory signalling pathways. In oncology, the abnormal expression of CD74 in various tumour cells correlates with tumour progression and prognosis.