title: CD45-protein tyrosine phosphatase cross-linking inhibits T cell receptor CD3-mediated activation in human T cells.
abstract: Activation of peripheral blood T cells, and the leukemic T cell line Jurkat, as measured by mobilization of intracellular calcium, by an anti-TCR antibody is blocked by mAb (T191) to the leukocyte common Ag (CD45). T191 also blocked down-regulation of the CD3-TCR complex induced by an anti-CD3 mAb. Vanadate, a phosphotyrosine phosphatase inhibitor, partially blocks the effect of T191 and restored mobilization of intracellular calcium. Assays of the immunoprecipitates of T191 and CD45 from both Jurkat-BM1 and peripheral T cells showed that the immune complexes had intrinsic phosphatase activity. A parallel immunoprecipitate using a mAb (4-10) against HLA class I showed no such activity. Further analysis of the T191 immunocomplex revealed activity against phosphotyrosine, p-nitrophenylphosphate, and [32P-poly-glu-tyr, but not against phosphoserine. Phosphatase activity was inhibited by Vanadate, but not by Zn2+ or F-. These results show that CD45 is a phosphotyrosine phosphatase, and strongly suggest that tyrosine phosphorylation/dephosphorylation is critically involved in activation of T cells through the TCR-CD3 complex.
authors.affiliation: Bristol-Myers Company, Department of Immunology, Wallingford, CT 06492-7660.
authors.forename: P A
authors.initials: PA
authors.lastname: Kiener
authors.forename: R S
authors.initials: RS
authors.lastname: Mittler
mesh_terms: D000911:Antibodies, Monoclonal / Q000502:physiology; D000943:Antigens, Differentiation / Q000276:immunology / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D001667:Binding, Competitive; D017252:CD3 Complex; D002460:Cell Line; D003432:Cross-Linking Reagents; D006649:Histocompatibility Antigens / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation / Q000187:drug effects; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000276:immunology / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D003432:Cross-Linking Reagents; D006649:Histocompatibility Antigens; D011948:Receptors, Antigen, T-Cell; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; D017493:Leukocyte Common Antigens