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CD74
CD74 Full Name
CD74 molecule, major histocompatibility complex, class II invariant chain
CD74 Introduction
CD74, also known as the invariant chain or HLA class II histocompatibility antigen gamma chain, is a non-polymorphic type II transmembrane glycoprotein that plays a central role in immune system function. It is encoded by the CD74 gene and is predominantly expressed on antigen-presenting cells (APCs) such as B cells, macrophages, and dendritic cells, although it can also be found on other cell types under certain conditions. In its classical role, CD74 acts as a molecular chaperone for major histocompatibility complex class II (MHC II) proteins, where it stabilizes newly synthesized MHC II α/β heterodimers in the endoplasmic reticulum (ER), prevents premature peptide loading, and directs their trafficking through endosomal/lysosomal compartments for antigen processing and presentation to CD4+ T cells. This antigen presentation function is critical for initiating and regulating adaptive immune responses. Additionally, CD74 serves as a high-affinity cell surface receptor for cytokines such as macrophage migration inhibitory factor (MIF) and D-dopachrome tautomerase (MIF-2), engaging co-receptors like CD44 or CXCR4 to activate intracellular signaling pathways—including ERK1/2 MAPK, PI3K/Akt, NF-κB, and AMPK—that influence cell survival, proliferation, and inflammation.
Figure 1.Primary functions of leukocyte differentiation antigen 74 (CD74).(Sources: Li QL, et al.; 2023)
Beyond its well-established immunological functions, CD74 has increasingly been recognized for its broader biological roles. Its interactions extend to non-MHC II partners such as the amyloid precursor protein (APP), where CD74 binding can modulate amyloid-beta production, suggesting potential relevance beyond classical antigen presentation. CD74 also impacts the development and function of immune cells, including B-cell maturation, T-cell selection in the thymus, and dendritic cell motility, and regulates trafficking of other membrane proteins like the angiotensin II type I receptor. Moreover, CD74 expression is not strictly limited to professional APCs; it can be upregulated in epithelial and other cell types during inflammation or tissue injury, where it may contribute to immune modulation and cellular stress responses.
Clinically, aberrant expression or dysregulation of CD74 is implicated in a range of diseases, making it a significant focus for research and therapeutic development. High CD74 expression is observed in various hematologic malignancies such as non-Hodgkin's lymphoma, multiple myeloma, and subsets of acute myeloid leukemia, where it supports tumor cell survival and proliferation and serves as a promising target for immunotherapy, including monoclonal antibodies and antibody-drug conjugates due to its rapid internalization upon binding. CD74 is also associated with solid tumors, and its expression correlates with immune cell infiltration and antigen presentation signatures in the tumor microenvironment, suggesting roles in immunotherapy response. Beyond cancer, CD74 is involved in inflammatory and autoimmune conditions and has been linked to cardiovascular diseases and inflammatory cytokine production after ischemia-reperfusion injury, highlighting its multifaceted contributions to pathology. Research tools such as CD74 antibodies, functional assays, and gene-editing models are widely used to investigate these roles and to support biomarker discovery and therapeutic strategy development.
Alternate Names for CD74
CD74; CD74 molecule; major histocompatibility complex; class II invariant chain; II; DHLAG; HLADG; Ia-GAMMA; HLA class II histocompatibility antigen gamma chain; p33; HLA-DR-gamma; MHC HLA-DR gamma chain; Ia-associated invariant chain; gamma chain of class II antigens; HLA-DR antigens-associated invariant chain; CD74 antigen (invariant polypeptide of major histocompatibility complex; class II antigen-associated); HuMax-CD74
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