Early during an immune response, dendritic cells (DC) interact closely with CD4+ T cells, and cross-talk between these cells can come in the form of tumour necrosis factor (TNF) superfamily ligand-receptor interactions. These signals are critical for the maturation, function and survival of DC, and thereby dictate the capacity of DC to prime a robust T cell response. Among these cues, helper T cell-expressed CD40L interaction with DC-expressed CD40 is required to fully mature DC for cross-priming of help-dependent CD8+ T cell responses. The lymphotoxin-beta receptor (LTβR) is another TNF family receptor on DC, and it’s ligands LTα1β2 and LIGHT are expressed on activated T cells. Since abrogated LTβR signaling impairs T cell immunity, we have examined whether LTαβ represents another possible helper T cell-derived cue for full DC maturation. However the LT pathway controls lymphoid tissue organization and DC homeostasis, a second possible mechanism explaining the necessity of LTβR signaling for T cell immunity. Here we dissect the role of helper T cell-expressed LTβR ligands and DC-intrinsic LTβR signaling, independent of DC homeostasis or lymphoid organization, in DC function and T cell immunity. Absence of LTα1β2 and not LIGHT on helper T cells results in compromised T cell priming by DC ex vivo, and LTβ-/- CD4+ T cell responses are impaired in vivo. Ag-specific CD4+ T cell-expressed LTα1β2 and DC-intrinsic LTβR signaling are required for an optimal cytotoxic T lymphocyte (CTL) response in vivo. While CD40 induces IL-12 and is required for CTL function, DC-intrinsic LTβR signaling is necessary for CTL activation and expansion, early up-regulation of CD86 and IFNα/β production. Our results reveal non-redundant roles for distinct TNF family receptors in enabling DC to program different features in Ag-specific CD8+ T cells.

Early during an immune response, dendritic cells (DC) interact closely with CD4+ T cells, and cross-talk between these cells can come in the form of tumour necrosis factor (TNF) superfamily ligand-receptor interactions. These signals are critical for the maturation, function and survival of DC, and thereby dictate the capacity of DC to prime a robust T cell response. Among these cues, helper T cell-expressed CD40L interaction with DC-expressed CD40 is required to fully mature DC for cross-priming of help-dependent CD8+ T cell responses. The lymphotoxin-beta receptor (LTβR) is another TNF family receptor on DC, and it’s ligands LTα1β2 and LIGHT are expressed on activated T cells. Since abrogated LTβR signaling impairs T cell immunity, we have examined whether LTαβ represents another possible helper T cell-derived cue for full DC maturation. However the LT pathway controls lymphoid tissue organization and DC homeostasis, a second possible mechanism explaining the necessity of LTβR signaling for T cell immunity. Here we dissect the role of helper T cell-expressed LTβR ligands and DC-intrinsic LTβR signaling, independent of DC homeostasis or lymphoid organization, in DC function and T cell immunity. Absence of LTα1β2 and not LIGHT on helper T cells results in compromised T cell priming by DC ex vivo, and LTβ-/- CD4+ T cell responses are impaired in vivo. Ag-specific CD4+ T cell-expressed LTα1β2 and DC-intrinsic LTβR signaling are required for an optimal cytotoxic T lymphocyte (CTL) response in vivo. While CD40 induces IL-12 and is required for CTL function, DC-intrinsic LTβR signaling is necessary for CTL activation and expansion, early up-regulation of CD86 and IFNα/β production. Our results reveal non-redundant roles for distinct TNF family receptors in enabling DC to program different features in Ag-specific CD8+ T cells.

Dendritic cells (DC) constitute a heterogeneous leukocyte population having in common a unique capacity to induce primary T cell responses and are therefore most attractive candidates for immunomodulatory strategies. Two populations of blood DC (CD11c+ CD123dim and CD11c– CD123high) have been defined so far. However, their direct isolation for experimental purposes is hampered by their low frequency and by the lack of selective markers allowing large scale purification from blood. Here we describe the monoclonal antibody (mAb) M-DC8, which was generated by immunizing mice with highly enriched blood DC. This mAb specifically reacts with 0.2–1% of blood leukocytes and enables their direct isolation by a one-step immunomagnetic procedure from fresh mononuclear cells. These cells can be differentiated from T cells, B cells, NK cells and monocytes using lineage-specific antibodies. M-DC8+ cells express HLA class II molecules, CD33 and low levels of the costimulatory molecules CD86 and CD40. Upon in vitro culture M-DC8+ cells spontaneously mature into cells with the phenotype of highly stimulatory cells as documented by the upregulation of HLA-DR, CD86 and CD40; in parallel CD80 expression is induced. M-DC8+ cells display an outstanding capacity to present antigen. In particular, they proved to be excellent stimulators of autologous mixed leukocyte reaction and to activate T cells against primary antigens such as keyhole limpet hemocyanin. Furthermore, they induce differentiation of purified allogeneic cytotoxic T cells into alloantigen-specific cytotoxic effector cells. While the phenotypical analysis reveals similarities with the two known blood DC populations, the characteristic expression of Fc=γRIII (CD16) and the M-DC8 antigen clearly defines them as a novel population of blood DC. The mAb M-DC8 might thus be a valuable tool to determine circulating DC for diagnostic purposes and to isolate these cells for studies of antigen-specific T cell priming. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Dendritic cells (DC) constitute a heterogeneous leukocyte population having in common a unique capacity to induce primary T cell responses and are therefore most attractive candidates for immunomodulatory strategies. Two populations of blood DC (CD11c+ CD123dim and CD11c– CD123high) have been defined so far. However, their direct isolation for experimental purposes is hampered by their low frequency and by the lack of selective markers allowing large scale purification from blood. Here we describe the monoclonal antibody (mAb) M-DC8, which was generated by immunizing mice with highly enriched blood DC. This mAb specifically reacts with 0.2–1% of blood leukocytes and enables their direct isolation by a one-step immunomagnetic procedure from fresh mononuclear cells. These cells can be differentiated from T cells, B cells, NK cells and monocytes using lineage-specific antibodies. M-DC8+ cells express HLA class II molecules, CD33 and low levels of the costimulatory molecules CD86 and CD40. Upon in vitro culture M-DC8+ cells spontaneously mature into cells with the phenotype of highly stimulatory cells as documented by the upregulation of HLA-DR, CD86 and CD40; in parallel CD80 expression is induced. M-DC8+ cells display an outstanding capacity to present antigen. In particular, they proved to be excellent stimulators of autologous mixed leukocyte reaction and to activate T cells against primary antigens such as keyhole limpet hemocyanin. Furthermore, they induce differentiation of purified allogeneic cytotoxic T cells into alloantigen-specific cytotoxic effector cells. While the phenotypical analysis reveals similarities with the two known blood DC populations, the characteristic expression of Fc=γRIII (CD16) and the M-DC8 antigen clearly defines them as a novel population of blood DC. The mAb M-DC8 might thus be a valuable tool to determine circulating DC for diagnostic purposes and to isolate these cells for studies of antigen-specific T cell priming. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.