title: Synergy between CD28 and CD9 costimulation for naive T-cell activation.
abstract: Our previous study demonstrated that CD9 is expressed on most mature naive T-cells and delivers a potent costimulatory signal that functions independently of CD28. Here, we investigated whether this CD9-mediated signal is different from the CD28-mediated signal in the mode of costimulation and whether both signals function synergistically for T-cell activation. Anti-CD9 or anti-CD28 monoclonal antibody (mAb) increased [3H]TdR incorporation of naive T-cells in the absence of antigen-presenting cells (APC) when coimmobilized with submitogenic doses of anti-CD3 mAb. The levels of costimulation induced by ligation of CD9 and CD28 were comparable. However, the costimulatory effect differed between soluble anti-CD9 and CD28 mAb. A soluble form of anti-CD28 mAb could costimulate anti-CD3-triggered T-cells, whereas soluble anti-CD9 mAb failed to costimulate. Although anti-CD28 costimulated naive T-cells treated with phorbol myristate acetate (PMA) instead of anti-CD3 mAb, a combination of PMA plus anti-CD9 mAb could not induce T-cell activation. The combined costimulation of anti-CD3-triggered T-cells with anti-CD9 and anti-CD28 mAbs resulted in strikingly enhanced [3H]TdR uptake and lymphokine (IL-2 and IFN-gamma) production when compared to those induced by each costimulation. These results suggest that CD9 and CD28 induce T-cell costimulation using different signaling pathways, thereby inducing synergy in T-cell activation.
authors.affiliation: Biomedical Research Center, Osaka University Medical School, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Toyo-oka
authors.forename: X G
authors.initials: XG
authors.lastname: Tai
authors.forename: Y
authors.initials: Y
authors.lastname: Yashiro
authors.forename: H J
authors.initials: HJ
authors.lastname: Ahn
authors.forename: R
authors.initials: R
authors.lastname: Abe
authors.forename: T
authors.initials: T
authors.lastname: Hamaoka
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Neben
authors.forename: H
authors.initials: H
authors.lastname: Fujiwara
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology*; D018106:CD28 Antigens / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D008198:Lymph Nodes / Q000166:cytology; D008213:Lymphocyte Activation / Q000276:immunology*; D008562:Membrane Glycoproteins; D051379:Mice; D008810:Mice, Inbred C57BL; D015398:Signal Transduction; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D060245:Tetraspanin 29
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018106:CD28 Antigens; D017252:CD3 Complex; C554870:Cd9 protein, mouse; D007376:Interleukin-2; D008562:Membrane Glycoproteins; D060245:Tetraspanin 29; D007371:Interferon-gamma; D013755:Tetradecanoylphorbol Acetate