title: Endothelial cell co-stimulation through OX40 augments and prolongs T cell cytokine synthesis by stabilization of cytokine mRNA.
abstract: Human endothelial cells (ECs) constitutively express OX40L and co-stimulate memory CD4(+) T cell proliferation that is dependent upon OX40-OX40L interaction. In vivo, OX40 prolongs T cell survival; however, an unanswered question is whether it can also prolong synthesis of proliferation-sustaining cytokines such as IL-2. Here we show that EC co-stimulation results in the secretion of T cell IL-2, IL-3 and IFN-gamma and that in the absence of OX40 signals synthesis largely ceases by 12-18 h, but is prolonged up to 60 h in the presence of OX40 signaling. Blocking OX40-mediated cytokine expression at later times suppresses T cell proliferation and this can be overcome by addition of exogenous IL-2. We find that OX40 signaling has discrete effects on T cell activation as it does not affect expression of IL-10, CD25, CD69 or soluble IL-2R. Also, OX40 does not appear to alter IL-2 transcription, but rather acts to stabilize a subset of cytokine mRNAs, increasing their half-lives by 3-6-fold. We further show that OX40L induces activation of p38 mitogen-activated protein kinase (MAPK) and phosphotidyl-inositol-3-kinase (PI3K) in T cells, and using specific inhibitors, we find that increased mRNA half-life is dependent upon both these pathways but is independent of c-jun-N-terminal kinase (JNK). Thus, EC co-stimulation through OX40 leads to prolonged T cell cytokine synthesis and enhanced proliferation.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.
authors.forename: Javier
authors.initials: J
authors.lastname: Mestas
authors.forename: Steve P
authors.initials: SP
authors.lastname: Crampton
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Hori
authors.forename: Christopher C W
authors.initials: CC
authors.lastname: Hughes
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002450:Cell Communication / Q000276:immunology; D049109:Cell Proliferation; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis* / Q000276:immunology; D042783:Endothelial Cells / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism; D053278:OX40 Ligand; D010766:Phosphorylation; D020871:RNA Stability; D012333:RNA, Messenger / Q000276:immunology / Q000378:metabolism; D053262:Receptors, OX40; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D048069:Tumor Necrosis Factors / Q000276:immunology / Q000378:metabolism; D014471:Umbilical Veins / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism
chemical_list: D016207:Cytokines; D008562:Membrane Glycoproteins; D053278:OX40 Ligand; D012333:RNA, Messenger; D053262:Receptors, OX40; D018124:Receptors, Tumor Necrosis Factor; C505716:TNFRSF4 protein, human; C089251:TNFSF4 protein, human; D048069:Tumor Necrosis Factors; D048051:p38 Mitogen-Activated Protein Kinases