CD3γ (F1D9A) Rabbit mAb #36193

When T cells encounter antigens via the T cell receptor (TCR), information about the quantity and quality of antigens is relayed to the intracellular signal transduction machinery (1). This activation process depends mainly on CD3 (Cluster of Differentiation 3), a multiunit protein complex that directly associates with the TCR. CD3 is composed of four polypeptides: ζ, γ, ε, and δ. Each of these polypeptides contains at least one immunoreceptor tyrosine-based activation motif (ITAM) (2). Engagement of the TCR complex with foreign antigens induces tyrosine phosphorylation in the ITAM motifs and phosphorylated ITAMs function as docking sites for signaling molecules such as ZAP-70 and the p85 subunit of PI-3 kinase (3,4). TCR ligation also induces a conformational change in CD3ε, such that a proline region is exposed and then associates with the adaptor protein Nck (5).

CD3γ is one of the invariant chains of the TCR signaling complex and is expressed at the cell surface as a type-I transmembrane glycoprotein, which forms a non-covalent heterodimer with CD3ε. Like other invariant chains of the TCR signaling complex, CD3γ contains a single ITAM with two embedded tyrosine residues that are likely directly phosphorylated by members of the Src family of tyrosine kinases to facilitate T cell activation (6,7). Research studies have demonstrated that CD3γ is also phosphorylated on serine residues, constituting a mechanism to downregulate TCR signaling through receptor internalization (8).