Goat polyclonal antibody to CD45. It is a 180-220 kDa type I transmembrane glycoprotein and a member of the protein tyrosine phosphatase (PTP) family. This PTP contains an extracellular domain, a single transmembrane segment and two tandem intracytoplasmic catalytic domains, and thus is classified as a receptor type PTP. It is expressed in all hematopoietic cells, but highest on lymphocytes. PTPs are known to be signalling molecules that regulate a variety of cellular processes including cell growth, differentiation, mitosis, and oncogenic transformation. It has intrinsic tyrosine phosphatase activity and it is essential for T and B cell antigen receptor-mediated activation. It functions through either direct interaction with components of the antigen receptor complexes, or by activating various Src family kinases required for the antigen receptor signalling. CD45 also suppresses JAK kinases, and thus functions as a regulator of cytokine receptor signalling. The cross-linking of CD45 induces apoptosis in lymphocytes.