Anti-CD4 Cytoplasmic Tail Antibody

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. {PubMed:16951326, PubMed:24942581, PubMed:2823150, PubMed:7604010}.; (Microbial infection) Primary receptor for human immunodeficiency virus-1 (HIV-1) (PubMed:2214026, PubMed:16331979, PubMed:9641677, PubMed:12089508). Down-regulated by HIV-1 Vpu (PubMed:17346169). Acts as a receptor for Human Herpes virus 7/HHV-7 (PubMed:7909607). {PubMed:12089508, PubMed:16331979, PubMed:17346169, PubMed:2214026, PubMed:7909607, PubMed:9641677}.

CD4 is a co-receptor of the T-cell receptor (TCR) and assists the TCR in communicating with antigen-presenting cells. The short cytoplasmic/intracellular tail of CD4 contains a special sequence of amino acids that allow it to recruit and interact with the tyrosine kinase Lck (lymphocyte-specific protein tyrosine kinase). When the TCR and CD4 bind to distinct regions of an antigen-presenting MHCII molecule, tyrosine kinase Lck bound to the cytoplasmic tail of CD4 tyrosine-phosphorylates immunoreceptor tyrosine activation motifs (ITAM) on the cytoplasmic domains of CD3 to amplify the signal generated by the TCR. Many functions have been assigned to the cytoplasmic tail of CD4 including anti-viral regulation (down/up regulation of CD4), T-cell maturation, activation and differentiation, and Lck signal transmission.