Specific CD45 Isoforms Regulate T Cell Ontogeny and Are Functionally Distinct in Modifying Immune Activation

The antigen receptor complex on the cell surface of T lymphocytes is one of the most modular signal transduction systems yet defined. This characteristic emanates from various mechanisms that promote intermolecular associations between the αβ T cell receptor and the enzymes that transduce the intracellular biological signal cascade (reviewed in 1). Among the multiple proteins that regulate cellular responses following T cell receptor (TCR) stimulation, the CD45 tyrosine phosphatase is a crucial effector. T lymphocytes that lack CD45 expression at the cell surface are unable to transmit immunologic activation signals that initiate from TCR interaction with antigen and major histocompatibility (MHC) molecules (2).