CD45RO is also known as protein tyrosine phosphatase receptor type C (PTPRC). It is a protein tyrosine phosphatase required for T-cell activation through the antigen receptor. CD45RO acts as a positive regulator of T-cell coactivation upon binding to DPP4. The first PTPase domain has enzymatic activity, while the second one seems to affect the substrate specificity of the first one. Upon T-cell activation, CD45RO recruits and dephosphorylates SKAP1 and FYN. It also dephosphorylates LYN, and thereby modulates LYN activity (By similarity)[taken from UniProtKB (Entry: P08575)].