title: CD28-mediated activation of resting human T cells without costimulation of the CD3/TCR complex.
abstract: Stimulation of resting human T cells by crosslinked CD28 monoclonal antibodies (mAb) induces some early signaling events but does not lead to IL-2 secretion and proliferation. The induction of these functions usually requires the delivery of additional signals such as that provided by costimulation of the T cell receptor (TCR). We analyzed the capacity of a panel of different CD28 mAb to induce cellular functions in purified human T cells. Two patterns of reactivity were observed. "Costimulatory" CD28 mAb like 9.3 required coengagement of the CD3/TCR complex for the induction of IL-2 gene transcription and proliferation. On the other hand, a "stimulatory" pathway could be defined by the use of the CD28 mAb BW 828, which triggered IL-2 synthesis, IL-2R expression, and proliferation without further requirement for additional stimuli. BW 828-induced proliferation was sensitive to inhibition by cyclosporin A and was mainly found in the CD4+CD45R0+ ("memory") T cell subset. These data suggest that T cell stimulation with mAb BW 828 defines a CD28-associated signaling pathway which leads to the induction of effector functions without the need for CD3/TCR coengagement. This pathway might play a role in antigen-independent activation and expansion of T cells.
authors.affiliation: Klinik für Abdominal- und Transplantationschirurgie Medizinische Hochschule Hannover, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Siefken
authors.forename: R
authors.initials: R
authors.lastname: Kurrle
authors.forename: R
authors.initials: R
authors.lastname: Schwinzer
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D018106:CD28 Antigens / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology*; D016572:Cyclosporine / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D017252:CD3 Complex; D007376:Interleukin-2; D015375:Receptors, Interleukin-2; D016572:Cyclosporine