Protein tyrosine-protein phosphatase required for T-cell activation through the antigen receptor. 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, recruits and dephosphorylates SKAP1 and FYN. Dephosphorylates LYN, and thereby modulates LYN activity (By similarity). (Microbial infection) Acts as a receptor for human cytomegalovirus protein UL11 and mediates binding of UL11 to T-cells, leading to reduced induction of tyrosine phosphorylation of multiple signaling proteins upon T-cell receptor stimulation and impaired T-cell proliferation. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Binds GANAB and PRKCSH (By similarity). Interacts with SKAP1 (PubMed:11909961). Interacts with DPP4; the interaction is enhanced in an interleukin-12-dependent manner in activated lymphocytes (PubMed:12676959). (Microbial infection) Interacts with human cytomegalovirus protein UL11; the interaction is required for binding of UL11 to T-cells. Colocalized with DPP4 in membrane rafts. Isoform 1: Detected in thymocytes. Isoform 2: Detected in thymocytes. Isoform 3: Detected in thymocytes. Isoform 4: Not detected in thymocytes. Isoform 5: Detected in thymocytes. Isoform 6: Not detected in thymocytes. Isoform 7: Detected in thymocytes. Isoform 8: Not detected in thymocytes. Isoform 1: During T-cell development, expressed at the CD3-CD4-CD8- and CD3+CD4+CD8- stages but barely detectable at the CD3-CD4+CD8+ stage. Isoform 2: During T-cell development, expressed at low levels at the CD3-CD4-CD8- and CD3-CD4+CD8- stages but up-regulated at the CD3+CD4+CD8+ and CD3+CD4+CD8- stages. Isoform 3: During T-cell development, expressed at the CD3-CD4-CD8- and CD3+CD4+CD8- stages but barely detectable at the CD3-CD4+CD8+ stage. Isoform 5: During T-cell development, expressed at the CD3-CD4-CD8- and CD3+CD4+CD8- stages but barely detectable at the CD3-CD4+CD8+ stage. Isoform 7: Consistently expressed at high levels at all stages of T-cell development. The first PTPase domain interacts with SKAP1. Heavily N- and O-glycosylated. The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility may be associated with variants affecting the gene represented in this entry. Belongs to the protein-tyrosine phosphatase family. Receptor class 1/6 subfamily. It is uncertain whether Met-1 or Met-3 is the initiator. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. PTPRC mutation db CD45 entry