Invitrogen™ CD8 Monoclonal Antibody (3B5), APC

CD8, also known as cluster of differentiation 8, is a type I transmembrane glycoprotein of the immunoglobulin family that plays a crucial role in T cell differentiation, activation, and signal transduction. It is expressed as either a heterodimer (CD8 alpha beta) or a homodimer (CD8 alpha alpha). The CD8 alpha beta form is predominantly found on the majority of thymocytes and a subpopulation of mature alpha beta TCR T cells, while the CD8 alpha alpha form is expressed on gamma delta TCR T cells, a subset of intestinal intraepithelial lymphocytes (IELs), and dendritic cells. CD8 functions as a co-receptor for major histocompatibility complex class I (MHC-I) molecules, working alongside the T cell receptor (TCR). The CD8 alpha chain is essential for binding to MHC-I. CD8 is also expressed on a subset of T cells, NK cells, monocytes, and dendritic cells as disulfide-linked homodimers of CD8 alpha. Upon ligation of MHC-I/peptide complexes presented by antigen-presenting cells (APCs), CD8 recruits lymphocyte-specific protein tyrosine kinase (Lck), leading to lymphokine production, increased motility, and activation of cytotoxic T lymphocytes (CTLs). Activated CTLs are vital for clearing pathogens and tumor cells. The differentiation of naive CD8+ T cells into CTLs is strongly enhanced by cytokines such as IL-2, IL-12, and TGF-beta1. Through its interactions with MHC-I and association with protein tyrosine kinase p56lck, CD8 plays a significant role in T cell development and the activation of mature T cells.