CD4 (cluster of differentiation 4) is a glycoprotein expressed on the surface of T helper cells, regulatory T cells, and dendritic cells. On T cells, CD4 is the co-receptor for the T cell receptor (TCR) and recruits the tyrosine kinase lck. With its D₁-portion it attaches to the β₂-domain of MHC class II molecules.

CD4 is also a primary receptor for binding of HIV-1 through the gp120 envelope protein. This binding leads to a shift in the protein conformation allowing HIV-1 to bind to ccr5 or cxcr4 and fuse with the cell membrane.

HIV infection leads to a progressive reduction in the number of T cells with CD4 receptors and the CD4 count is used as a staging indicator to help decide when to begin treatment.

See also

• Lck gene
• List of human clusters of differentiation

External link

• NCBI gene info

Clusters of differentiation

CD4-Rezeptor | CD4 | CD4 | CD4 | CD4