title: Human CD14hi monocytes and myeloid dendritic cells provide a cell contact-dependent costimulatory signal for early CD40 ligand expression.
abstract: CD40L on CD4(+) T cells plays a vital role in the activation of antigen-presenting cells, thus catalyzing a positive feedback loop for T-cell activation. Despite the pivotal juxtaposition of CD40L between antigen-presenting cells and T-cell activation, only a T-cell receptor stimulus is thought to be required for early CD40L surface expression. We show, for the first time, that CD40L expression on peripheral blood CD4(+) T cells is highly dependent on a cell-cell interaction with CD14(hi)CD16(-) monocytes. Interactions with ICAM-1, LFA-3, and to a lesser extent CD80/CD86 contribute to this enhancement of CD40L expression but are not themselves sufficient. The contact-mediated increase in CD40L expression is dependent on new mRNA and protein synthesis. Circulating myeloid dendritic cells also possess this costimulatory activity. By contrast, CD14(lo)CD16(+) monocytes, plasmacytoid dendritic cells, B-cell lymphoma lines, and resting, activated, and Epstein-Barr virus-immortalized primary B cells all lack the capacity to up-regulate early CD40L. The latter indicates that a human B cell cannot activate its cognate T cell to deliver CD40L-mediated help. This finding has functional implications for the role of biphasic CD40L expression, suggesting that the early phase is associated with antigen-presenting cell activation, whereas the late phase is related to B-cell activation.
authors.affiliation: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Sagarika
authors.initials: S
authors.lastname: Chakrabarty
authors.forename: James T
authors.initials: JT
authors.lastname: Snyder
authors.forename: Jijia
authors.initials: J
authors.lastname: Shen
authors.forename: Hooman
authors.initials: H
authors.lastname: Azmi
authors.forename: Paul Q
authors.initials: PQ
authors.lastname: Hu
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.forename: Jack A
authors.initials: JA
authors.lastname: Ragheb
mesh_terms: D000938:Antigen-Presenting Cells; D015152:Blotting, Northern; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes; D019013:CD40 Antigens / Q000378:metabolism*; D023201:CD40 Ligand / Q000235:genetics / Q000378:metabolism*; D018968:CD58 Antigens / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion; D002450:Cell Communication; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism*; D008213:Lymphocyte Activation; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D022423:Myeloid Cells / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D019013:CD40 Antigens; D018968:CD58 Antigens; D018950:Lipopolysaccharide Receptors; D012333:RNA, Messenger; D018799:Intercellular Adhesion Molecule-1; D023201:CD40 Ligand