Human T-cell surface glycoprotein CD4 (CD4)

Human T-cell surface glycoprotein CD4 is a type I transmembrane glycoprotein of approximately 58 kDa, primarily expressed on the surface of immune cells such as helper T cells (CD4+), monocytes, macrophages, and dendritic cells[3][8]. Structurally, it consists of four extracellular immunoglobulin-like domains (D1–D4), a single transmembrane region, and a cytoplasmic tail that interacts with key signaling molecules, notably the tyrosine kinase Lck[1][3][5]. CD4 acts as a co-receptor for the T-cell receptor (TCR), binding to non-polymorphic regions of the MHC class II molecule presented by antigen-presenting cells, thereby enhancing TCR-mediated signal transduction and facilitating T cell activation[3][5]. CD4 is the principal receptor for the HIV-1 envelope glycoprotein gp120, mediating the entry of the virus into host cells and resulting in CD4+ T cell depletion that characterizes AIDS[4][5]. Measurement of peripheral blood CD4+ T cell count is a standard biomarker for assessing immune status in HIV-infected patients and immune surveillance in various clinical contexts[3][8]. CD4 is a validated therapeutic target for drug development in HIV infection, transplantation immunomodulation, immune depletion strategies, and as a biomarker in certain malignancies and autoimmune disorders[6].

Other names

T-cell surface antigen T4Leu-3T4 antigenOKT4Cluster of differentiation 4

HIV entry inhibition (by blocking gp120-CD4 interaction); Immune modulation (depleting or stimulating CD4+ T cells); Antibody-dependent cellular cytotoxicity (ADCC, by mAbs targeting CD4)