title: Inhibition of CD28-mediated T cell costimulation by the phosphoinositide 3-kinase inhibitor wortmannin.
abstract: T lymphocyte activation requires at least two signals, one via the antigen-specific T cell receptor and a second via the surface molecule CD28 which provides signals critical to interleukin-2 (IL-2) production and T cell proliferation. We have previously shown (Ward S. G., Westwick, J., Hall N. and Sansom D. M. Eur. J. Immunol. 1993. 23: 2572) that CD28 stimulates phosphoinositide (PI) 3-kinase activity, indicating that D-3 phosphoinositides may act as mediators of CD28-induced T cell costimulation. Here, we report that immunoprecipitation of CD28 molecules from Jurkat cells stimulated with the CD28-ligand B7, results in a ligand-dependent association of CD28 with PI 3-kinase. This association correlates with the appearance of PI 3-kinase enzymatic activity in CD28 immunoprecipitates and the formation of D-3 phosphoinositides. Consistent with the hypothesis that D-3 phosphoinositides are important mediators of CD28 signaling, treatment of T cells with the PI 3-kinase inhibitor wortmannin, inhibited both T cell proliferation and production of IL-2, but not the response of T cells to exogenous IL-2. Hence, abrogation of PI 3-kinase activity by wortmannin, appears sufficient to disrupt the costimulatory pathway utilized by CD28, indicating a central role for this enzyme in the CD28 signaling pathway.
authors.affiliation: University of Bath, School of Pharmacy and Pharmacology, Clarerton Down.
authors.forename: S G
authors.initials: SG
authors.lastname: Ward
authors.forename: A
authors.initials: A
authors.lastname: Wilson
authors.forename: L
authors.initials: L
authors.lastname: Turner
authors.forename: J
authors.initials: J
authors.lastname: Westwick
authors.forename: D M
authors.initials: DM
authors.lastname: Sansom
mesh_terms: D000730:Androstadienes / Q000494:pharmacology*; D018106:CD28 Antigens / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors* / Q000502:physiology; D013601:T-Lymphocytes / Q000502:physiology*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D018106:CD28 Antigens; D007376:Interleukin-2; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D002118:Calcium; D000077191:Wortmannin