CD4 Antibody - #AF5341

Integral membrane glycoprotein that plays an essential role in the immune response and serves multiple functions in responses against both external and internal offenses. In T-cells, functions primarily as a coreceptor for MHC class II molecule:peptide complex. The antigens presented by class II peptides are derived from extracellular proteins while class I peptides are derived from cytosolic proteins. Interacts simultaneously with the T-cell receptor (TCR) and the MHC class II presented by antigen presenting cells (APCs). In turn, recruits the Src kinase LCK to the vicinity of the TCR-CD3 complex. LCK then initiates different intracellular signaling pathways by phosphorylating various substrates ultimately leading to lymphokine production, motility, adhesion and activation of T-helper cells. In other cells such as macrophages or NK cells, plays a role in differentiation/activation, cytokine expression and cell migration in a TCR/LCK-independent pathway. Participates in the development of T-helper cells in the thymus and triggers the differentiation of monocytes into functional mature macrophages.

(Microbial infection) Primary receptor for human immunodeficiency virus-1 (HIV-1). Down-regulated by HIV-1 Vpu. Acts as a receptor for Human Herpes virus 7/HHV-7.

Palmitoylation and association with LCK contribute to the enrichment of CD4 in lipid rafts.

Phosphorylated by PKC; phosphorylation at Ser-433 plays an important role for CD4 internalization.

Cell membrane>Single-pass type I membrane protein.
Note: Localizes to lipid rafts (PubMed:12517957, PubMed:9168119). Removed from plasma membrane by HIV-1 Nef protein that increases clathrin-dependent endocytosis of this antigen to target it to lysosomal degradation. Cell surface expression is also down-modulated by HIV-1 Envelope polyprotein gp160 that interacts with, and sequesters CD4 in the endoplasmic reticulum.

Highly expressed in T-helper cells. The presence of CD4 is a hallmark of T-helper cells which are specialized in the activation and growth of cytotoxic T-cells, regulation of B cells, or activation of phagocytes. CD4 is also present in other immune cells such as macrophages, dendritic cells or NK cells.

Forms disulfide-linked homodimers at the cell surface. Interacts with LCK. Interacts with PTK2/FAK1. Binds to P4HB/PDI. Interacts with IL16; this interaction induces a CD4-dependent signaling in lymphocytes.

(Microbial infection) Interacts with HIV-1 Envelope polyprotein gp160 and protein Vpu.

(Microbial infection) Interacts with Human Herpes virus 7 surface proteins.