title: CD40-CD40 ligand interaction between dendritic cells and CD8+ T cells is needed to stimulate maximal T cell responses in the absence of CD4+ T cell help.
abstract: Stimulation of CD40 on APCs through CD40L expressed on helper CD4+ T cells activates and "licenses" the APCs to prime CD8+ T cell responses. Although other stimuli, such as TLR agonists, can also activate APCs, it is unclear to what extent they can replace the signals provided by CD40-CD40L interactions. In this study, we used an adoptive transfer system to re-examine the role of CD40 in the priming of naive CD8+ T cells. We find an approximately 50% reduction in expansion and cytokine production in TCR-transgenic T cells in the absence of CD40 on all APCs, and on dendritic cells in particular. Moreover, CD40-deficient and CD40L-deficient mice fail to develop endogenous CTL responses after immunization. Surprisingly, the role for CD40 and CD40L are observed even in the absence of CD4+ T cells; in this situation, the CD8+ T cell itself provides CD40L. Furthermore, we show that although TLR stimulation improves T cell responses, it cannot fully substitute for CD40. Altogether, these results reveal a direct and unique role for CD40L on CD8+ T cells interacting with CD40 on APCs that affects the magnitude and quality of CD8+ T cell responses.
authors.affiliation: Department of Pathology and Program in Immunology and Virology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
authors.forename: Maria Genevive H
authors.initials: MG
authors.lastname: Hernandez
authors.forename: Lianjun
authors.initials: L
authors.lastname: Shen
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Rock
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D019013:CD40 Antigens / Q000172:deficiency / Q000276:immunology*; D023201:CD40 Ligand / Q000172:deficiency / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002450:Cell Communication / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D051193:Toll-Like Receptors / Q000819:agonists / Q000276:immunology
chemical_list: D019013:CD40 Antigens; D051193:Toll-Like Receptors; D023201:CD40 Ligand