PTPRC is also known as CD45 antigen, which was originally called leukocyte common antigen (LCA). The encoded protein is 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 belongs to receptor type PTP, specifically expressed in hematopoietic cells. This PTP has been shown to be an essential regulator of T- and B-cell antigen receptor signaling. 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 signaling. It also suppresses JAK kinases and functions as a negative regulator of cytokine receptor signaling.