Human HLA Class II Histocompatibility Antigen Gamma Chain (CD74) Protein

Background

CD74, also known as the invariant chain (Ii), is a type II transmembrane glycoprotein that plays a critical role in the immune system, particularly in antigen processing and presentation. CD74 is encoded by the CD74 gene and is primarily expressed on antigen-presenting cells (APCs) such as B cells, dendritic cells, and macrophages, although it is also found on some non-immune cells, including certain epithelial and cancer cells. One of its central functions is to act as a chaperone for major histocompatibility complex class II (MHC-II) molecules, ensuring the proper folding, trafficking, and peptide loading of MHC-II, which is essential for the presentation of antigens to CD4+ T cells. In addition to its role in antigen presentation, CD74 also functions as a receptor for macrophage migration inhibitory factor (MIF), which modulates inflammatory responses and cell survival pathways.