Biomedical subjects

B Ludewig

Publications and source records attributed to B Ludewig.

25 records · Page 2Linked to original sources

PubMed1998

Dendritic cells efficiently induce protective antiviral immunity.

Cytotoxic T lymphocytes (CTL) are essential for effective immunity to various viral infections. Because of the high speed of viral replication, control of viral infections imposes demanding functional and qualitative requirements on protective T-cell responses. Dendritic cells (DC) have been shown to efficiently acquire, transport, and present antigens to naive CTL in vitro and in vivo. In this study, we assessed the potential of DC, either pulsed with the lymphocytic choriomeningitis virus (LCMV)-specific peptide GP33-41 or constitutively expressing the respective epitope, to induce LCMV-specific antiviral immunity in vivo. Comparing different application routes, we found that only 100 to 1,000 DC had to reach the spleen to achieve protective levels of CTL activation. The DC-induced antiviral immune response developed rapidly and was long lasting. Already at day 2 after a single intravenous immunization with high doses of DC (1 x 10(5) to 5 x 10(5)), mice were fully protected against LCMV challenge infection, and direct ex vivo cytotoxicity was detectable at day 4 after DC immunization. At day 60, mice were still protected against LCMV challenge infection. Importantly, priming with DC also conferred protection against infections in which the homing of CTL into peripheral organs is essential: DC-immunized mice rapidly cleared an infection with recombinant vaccinia virus-LCMV from the ovaries and eliminated LCMV from the brain, thereby avoiding lethal choriomeningitis. A comparison of DC constitutively expressing the GP33-41 epitope with exogenously peptide-pulsed DC showed that in vivo CTL priming with peptide-loaded DC is not limited by turnover of peptide-major histocompatibility complex class I complexes. We conclude that the priming of antiviral CTL responses with DC is highly efficient, rapid, and long lasting. Therefore, the use of DC should be considered as an efficient means of immunization for antiviral vaccination strategies.

Animals↗

PubMed1997

Monocyte-derived dendritic cells represent a transient stage of differentiation in the myeloid lineage.

Cultivation of human peripheral blood monocytes with granulocyte/macrophage colony stimulating factor (GM-CSF) and IL-4 facilitates generation of strongly antigen-presenting dendritic cells (DC). These monocyte-derived DC (mdDC) were used here to further delineate differentiation pathways in the myeloid lineage. Incubation of mdDC with TNF or soluble CD40L led to enhanced MHC and accessory surface antigen expression with significantly elevated T cell stimulatory activity, indicative of DC maturation. In contrast, after cytokine withdrawal or incubation with M-CSF, mdDC differentiated to macrophages. Cells became adherent, monocyte/macrophage surface markers were upregulated, and MHC and accessory surface proteins were downregulated. Furthermore, the multilaminar MHC class II compartments (MIIC) were lost and the T cell stimulating capacity largely diminished. Thus, mdDC show a high developmental plasticity by retaining their ability to become macrophages or to continue their differentiation towards mature DC.

Antigen Presentation↗

PubMed1996

Transmission of HIV-1 from productively infected mature Langerhans cells to primary CD4+ T lymphocytes results in altered T cell responses with enhanced production of IFN-gamma and IL-10.

Mature Langerhans cells (mLC), the ex vivo correlates of interdigitating dendritic cells (IDC), are susceptible to infection with HIV-1. As IDC are important activators of T helper (Th) cells in vivo, we examined the interaction of HIV-1-infected mLC with CD4+ T lymphocytes. HIV-1-infected mLC readily formed clusters with the T cells and efficiently transmitted HIV-1 to the CD4+ Th cells. Formation of syncytia between mLC and T cells was initiated by HIV-1-infected mLC. In the clusters of HIV-1-infected mLC and activated T cells a massive HIV-1 production was observed leading to the subsequent elimination of the activated and infected T helper cells. Examination of the cytokine pattern produced during interaction of infected mLC with CD4+ T cells revealed an enhanced production of IFN-gamma and IL-10 in the cocultures. These results suggest that during antigen presentation-driven T cell activation by IDC in the lymphoid tissues, HIV-1-infected IDC might efficiently transmit the virus to Th cells, leading to altered Th cell responses.

CD4-Positive T-Lymphocytes↗

PubMed1996

Induction, regulation, and function of soluble TRAP (CD40 ligand) during interaction of primary CD4+ CD45RA+ T cells with dendritic cells.

To assess the induction, regulation, and the relative roles of cell surface tumor necrosis factor-related activation protein (TRAP; CD40 ligand) and the soluble form of TRAP (sTRAP) in the initial phase of T cell activation, primary CD4+ CD45RA+ (naive) T cells were co-cultured with mature Langerhans' cells (mLC) in the presence of superantigen. In this cell system, TRAP was very efficiently induced in T cells at both the mRNA and protein levels. After appearing on the cell surface, TRAP was rapidly down-regulated by a mechanism triggered through interaction of TRAP with CD40 on mLC. Co-culture of T cells with mLC led to the release of sTRAP, an 18-kDa protein capable of binding to CD40. Experimental data strongly suggest that sTRAP is not released by proteolytic cleavage of TRAP on the cell surface, but is generated in an intracellular compartment. Release of sTRAP and induction of TRAP cell surface expression were found to be regulated independently. In terms of function, sTRAP cannot compete with cell surface TRAP for ligation of CD40 on mLC, indicating that sTRAP release is not a mechanism for termination of the TRAP/CD40 interaction. However, sTRAP on its own rapidly down-regulates CD40 expression on mLC and has long-lasting anti-apoptotic effects on dendritic cells. Thus, we infer from our results obtained in vitro that primary activation of CD4+ T cells by dendritic cells in the lymphoid tissues leads to release of sTRAP, which may act on CD40+ bystander cells in a cytokine-like fashion.

Adult↗

PubMed1995

Spontaneous apoptosis of dendritic cells is efficiently inhibited by TRAP (CD40-ligand) and TNF-alpha, but strongly enhanced by interleukin-10.

In the lymphoid tissues, adaptive immune responses are initiated by the interaction of interdigitating dendritic cells (IDC) with naive T cells. To understand this interplay better, we used mature Langerhans cells (mLC), migrating from human epidermis, as the correlate of IDC ex vivo to evaluate the different effects of tumor necrosis factor (TNF)-alpha. TNF-related activation protein (TRAP; CD40-ligand) and interleukin-10 (IL-10) on induction or prevention of apoptotic cell death in these cells. Spontaneous decrease of mLC viability in culture was due to apoptosis, as determined by the appearance of typical morphological changes such as dilatation of the endoplasmic reticulum (ER), chromatin condensation and membrane blebbing. IL-10 strongly reduced mLC viability, whereas TRAP and TNF-alpha facilitated the survival of mLC. Spontaneous DNA fragmentation was detectable after 24 h in culture. IL-10 led to an earlier onset of DNA fragmentation, whereas TRAP and TNF-alpha delayed internucleosomal DNA cleavage. We found that IL-10-treated mLC were readily ingested and removed by macrophages. TNF-alpha and TRAP, in contrast, reduced engulfment of mLC by macrophages. Interestingly, IL-10, even at low concentrations, reverted the effects of TNF-alpha and TRAP in inhibiting mLC apoptosis. Furthermore, IL-10 led to the down-regulation of various surface antigens, especially of CD86 and CD54, whereas TNF-alpha and TRAP enhanced the expression of MHC class I and II antigens and of the accessory molecules CD40, CD54, CD80 and CD86. Taken together, these results show that mLC spontaneously undergo apoptosis in culture and that the progression of mLC to apoptosis is inhibited by TRAP and TNF-alpha, but accelerated by IL-10.

Apoptosis↗

PubMed1995

Replication pattern of human immunodeficiency virus type 1 in mature Langerhans cells.

Langerhans cells (LC), the dendritic antigen presenting cells of the skin, mature into potent immunostimulatory cells during migration to regional lymph nodes, where they are identified as interdigitating cells (IDC). Since mature Langerhans cells (mLC) resemble IDC in phenotype and immunostimulatory capacity, we examined whether these cells were susceptible to infection with macrophagetropic and lymphotropic strains of human immunodeficiency virus type 1 (HIV-1). Highly purified cell preparations of mLC migrating from human epidermis expressed high amounts of major histocompatibility complex (MHC) class I and II antigens and of the accessory molecules CD40, CD80 and CD86, indicative of the phenotype of potent immunostimulatory cells. CD4 expression was upregulated on mLC during cultivation, independent of the presence of tumour necrosis factor alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the culture medium. The macrophagetropic HIV-1 strain SF162 replicated to higher titres in mLC than the lymphotropic strain IIIB. Both strains induced syncytia, with SF162 showing a more rapid cytopathic effect. Addition of TNF-alpha enhanced virus production, due to better cell viability under TNF-alpha treatment, whereas GM-CSF did not significantly influence viability of cells and replication pattern of the virus. These findings suggest that in the infected individual IDC in lymph nodes may function as target cells for HIV-1.

Antibodies, Monoclonal↗

PubMed1993

Sequence specific binding of the transcription factor c-Ets1 to the human immunodeficiency virus type I long terminal repeat.

Human immunodeficiency virus type I (HIV-1) long terminal repeat (LTR) driven transcription is regulated by a variety of cellular transcription factors. Most work has focused on the two nuclear factor kappa B (NF-kB) elements indispensable for HIV-1 LTR enhancer function. We demonstrate here the specific binding of the transcription factor c-Ets1 to an U3 region of the HIV-1 LTR (nt -141 to -149) using electrophoretic mobility shift analysis with T-cell nuclear extract and in vitro translated protein. This previously not identified Ets binding site is highly conserved among different HIV-1 isolates and maps to an U3 region recently shown to be necessary for viral growth in vitro. The c-Ets proto-oncogene family of transcription factors has yet been associated with HTLV-I and HIV-2 transcription. Our present analysis suggests an important role of c-Ets proteins in HIV-1 transcription.

Base Sequence↗