CD4 glycoprotein (CD4)

CD4 glycoprotein is a transmembrane protein comprising four extracellular immunoglobulin-like domains. It functions as a crucial co-receptor for T-cell receptor (TCR) recognition of antigen-presenting MHC class II on antigen-presenting cells, amplifying intracellular signaling via recruitment of the tyrosine kinase Lck, which phosphorylates immunoreceptor tyrosine activation motifs (ITAMs) on the CD3 complex. CD4 is also the primary cellular receptor for the HIV-1 envelope glycoprotein gp120. This interaction triggers conformational changes in the viral envelope that are necessary for the fusion of viral and host cell membranes. The receptor's extracellular domains are well-characterized structurally, with binding sites for MHC II as well as HIV gp120 located on the D1 domain. Therapeutically, CD4 is targeted to prevent HIV entry and is widely used as an immune biomarker, with CD4+ T-cell counts being a cornerstone for clinical monitoring in HIV/AIDS. CD4-targeted treatments must balance antiviral efficacy against the risk of immune suppression.

Other names

T-cell surface glycoprotein CD4Helper T-cell markerCluster of Differentiation 4

Blockade of HIV gp120 binding to CD4, preventing viral entry Modulation of immune activation via CD4–MHC II interaction