title: The role of CD40 in peripheral T cell tolerance and immunity.
abstract: CD40 and CD40 ligand (CD40L) have been implicated as important molecules for the transformation of nonactivated antigen-presenting cells (APC) into cells that are potent inducers of cytotoxic T lymphocyte (CTL) immunity. The onset of a successful immune response lies within the control of the CD4+ T helper cells which, after specific antigen recognition, can up-regulate CD40L and subsequently activate APC through CD40 signaling. Triggering of CD40 with antibodies in vivo can replace the need for CD40L-expressing CD4+ T helper cells for cross-priming of CTL. Blocking of CD40-CD40L interactions can also have profound effects on the generation of T cell immunity. Interestingly, differential involvement of CD40/CD40L in immune responses can be observed between various immunological sites in the body. In most sites of the periphery interruption of CD40-CD40L interactions can lead to the induction of T cell tolerance whereas in mucosal tissues this interruption can lead to abrogation of T cell tolerance. Furthermore, in vivo CD40 activation can convert specific T cell tolerance following peptide vaccination into efficient T cell priming. Thus intervention of CD40-CD40L interactions can result in enhancement or down-modulation of T cell reactivity and therefore modulation of these interactions may form the foundation of new treatment modalities directed against malignancies, allergies, organ rejections and autoimmunity.
authors.affiliation: Department of Immunohematology and Blood Transfusion, Medical Center, Leiden University, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Diehl
authors.forename: A T
authors.initials: AT
authors.lastname: Den Boer
authors.forename: E I
authors.initials: EI
authors.lastname: van der Voort
authors.forename: C J
authors.initials: CJ
authors.lastname: Melief
authors.forename: R
authors.initials: R
authors.lastname: Offringa
authors.forename: R E
authors.initials: RE
authors.lastname: Toes
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D019013:CD40 Antigens / Q000502:physiology*; D023201:CD40 Ligand / Q000502:physiology; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000502:physiology; D008213:Lymphocyte Activation; D008954:Models, Biological; D010455:Peptides / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D015854:Up-Regulation; D014612:Vaccines / Q000276:immunology
chemical_list: D019013:CD40 Antigens; D015395:Histocompatibility Antigens Class I; D010455:Peptides; D014612:Vaccines; D023201:CD40 Ligand