title: Phosphotyrosine phosphatases are involved in reversion of T lymphoblastic proliferation.
abstract: Resting T lymphocytes can be activated by mitogens or antigens to become T blasts, which revert spontaneously both in vivo and in vitro in extended cultures to secondary, memory T lymphocytes. We have studied the role of phosphotyrosine phosphatases (PTPase) in the reversion of lymphoblasts in extended, phyto-hemagglutinin-stimulated cultures of human T lymphocytes. Membrane-associated PTPase activity is high in resting T cells, but decreased during mitogen-induced blast transformation. When the blasts were reverting to lymphocytes, the PTPase activity increased more than twofold concomitantly with an elevated surface expression of CD45. When T blasts from phytohemagglutinin-activated cultures were kept in the presence of sodium orthovanadate, an inhibitor of PTPase, they maintained their lymphoblastic proliferation and did not revert to resting lymphocytes. This was accompanied by retention of a 48-kDa phosphotyrosine-containing protein. Our data indicate an important role for PTPase in the transition of lymphocytes from an activated to a resting stage.
authors.affiliation: Department of Pathology, University of Helsinki, Finland.
authors.forename: A V
authors.initials: AV
authors.lastname: Iivanainen
authors.forename: C
authors.initials: C
authors.lastname: Lindqvist
authors.forename: T
authors.initials: T
authors.lastname: Mustelin
authors.forename: L C
authors.initials: LC
authors.lastname: Andersson
mesh_terms: D000943:Antigens, Differentiation / Q000032:analysis; D006649:Histocompatibility Antigens / Q000032:analysis; D006801:Humans; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D017027:Protein Tyrosine Phosphatases; D013601:T-Lymphocytes / Q000276:immunology*; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000943:Antigens, Differentiation; D006649:Histocompatibility Antigens; D014638:Vanadates; D010749:Phosphoprotein Phosphatases; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases