title: The roles of CD28 and CD40 ligand in T cell activation and tolerance.
abstract: Costimulation of T cell activation involves both the B7:CD28 as well as the CD40 ligand (CD40L):CD40 pathway. To determine the importance of these pathways to in vitro and in vivo T cell activation, a direct comparison was made of the responses of TCR transgenic T cells lacking either CD28 or CD40L. In vitro, CD28-/- T cells showed a greater reduction in proliferative responses to Ag than did CD40L-/- T cells. The absence of CD28 resulted in defective Th2 responses, whereas CD40L-/- T cells were defective in Th1 development. In vivo, CD28-/- T cells failed to expand upon immunization, whereas CD40L-/- T cells could not sustain a response. These results suggest that CD28 is critical for initiating T cell responses, whereas CD40L is required for sustained Th1 responses. The different functional roles of these costimulatory pathways may explain why blocking B7:CD28 and CD40L:CD40 interactions has an additive effect in inhibiting T cell responses.
authors.affiliation: Immunology Research Division, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Howland
authors.forename: L J
authors.initials: LJ
authors.lastname: Ausubel
authors.forename: C A
authors.initials: CA
authors.lastname: London
authors.forename: A K
authors.initials: AK
authors.lastname: Abbas
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D018106:CD28 Antigens / Q000235:genetics / Q000502:physiology*; D019013:CD40 Antigens / Q000378:metabolism*; D023201:CD40 Ligand; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D007108:Immune Tolerance / Q000235:genetics; D008024:Ligands; D008213:Lymphocyte Activation / Q000235:genetics; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008822:Mice, Transgenic; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism* / Q000637:transplantation; D018417:Th1 Cells / Q000166:cytology / Q000276:immunology; D018418:Th2 Cells / Q000166:cytology / Q000276:immunology
chemical_list: D018106:CD28 Antigens; D019013:CD40 Antigens; D008024:Ligands; D008562:Membrane Glycoproteins; D023201:CD40 Ligand