Clone REA673 recognizes the human Lck antigen, phosphorylated at tyrosine 505. Lck is a non-receptor tyrosine-protein kinase that plays an essential role in the selection and maturation of developing T cells in the thymus and in the function of mature T cells. It is expressed at all stages of thymocyte development and is required for the regulation of maturation events that are governed by both pre-TCR and mature α/β TCR. Lck plays a key role in the T cell antigen receptor (TCR)–linked signal transduction pathways and is constitutively associated with the cytoplasmic portions of the CD4 and CD8 surface receptors. Association of the TCR with a peptide antigen-bound MHC complex facilitates the interaction of CD4 and CD8 with MHC class II and class I molecules, respectively, thereby recruiting the associated Lck protein to the vicinity of the TCR/CD3 complex. Lck then phosphorylates tyrosines residues within the immunoreceptor tyrosine-based activation motifs of the cytoplasmic tails of the TCR-γ chains and CD3 subunits, initiating the TCR/CD3 signaling pathway. Lck also contributes to signaling by other receptor molecules. It associates directly with the cytoplasmic tail of CD2, which leads to hyperphosphorylation and activation of Lck, and also plays a role in the IL-2 receptor-linked signaling pathway that controls the T cell proliferative response. Binding of IL-2 to its receptor results in increased activity of Lck. Phosphorylated Tyr-505 associates with the SH2 domain in the amino-terminal half of the protein.

Additional information: Clone REA673 displays negligible binding to Fc receptors.