title: A role for CD9 molecules in T cell activation.
abstract: Costimulation mediated by the CD28 molecule plays an important role in optimal activation of T cells. However, CD28-deficient mice can mount effective T cell-dependent immune responses, suggesting the existence of other costimulatory systems. In a search for other costimulatory molecules on T cells, we have developed a monoclonal antibody (mAb) that can costimulate T cells in the absence of antigen-presenting cells (APC). The molecule recognized by this mAb, 9D3, was found to be expressed on almost all mature T cells and to be a protein of approximately 24 kD molecular mass. By expression cloning, this molecule was identified as CD9, 9D3 (anti-CD9) synergized with suboptimal doses of anti-CD3 mAb in inducing proliferation by virgin T cells. Costimulation was induced by independent ligation of CD3 and CD9, suggesting that colocalization of these two molecules is not required for T cell activation. The costimulation by anti-CD9 was as potent as that by anti-CD28. Moreover, anti-CD9 costimulated in a CD28-independent way because anti-CD9 equally costimulated T cells from the CD28-deficient as well as wild-type mice. Thus, these results indicate that CD9 serves as a molecule on T cells that can deliver a potent CD28-independent costimulatory signal.
authors: Biomedical Research Center, Osaka University Medical School, Japan.
authors: X G
authors: XG
authors: Tai
authors: Y
authors: Y
authors: Yashiro
authors: R
authors: R
authors: Abe
authors: K
authors: K
authors: Toyooka
authors: C R
authors: CR
authors: Wood
authors: J
authors: J
authors: Morris
authors: A
authors: A
authors: Long
authors: S
authors: S
authors: Ono
authors: M
authors: M
authors: Kobayashi
authors: T
authors: T
authors: Hamaoka
authors: S
authors: S
authors: Neben
authors: H
authors: H
authors: Fujiwara
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000502:physiology*; D018106:CD28 Antigens / Q000502:physiology; D017252:CD3 Complex / Q000276:immunology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D013601:T-Lymphocytes / Q000276:immunology*; D060245:Tetraspanin 29
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018106:CD28 Antigens; D017252:CD3 Complex; C554870:Cd9 protein, mouse; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D060245:Tetraspanin 29