Biomedical subjects

Christine Heufler

Publications and source records attributed to Christine Heufler.

9 recordsLinked to original sources

PubMed2005

Dendritic cells regulate T-cell deattachment through the integrin-interacting protein CYTIP.

When T cells are primed by dendritic cells (DCs) to initiate antigen-specific immune responses screening for matching antigen receptor-MHC/peptide pairs takes place in DC-T-cell conjugates. For an immune response DC-T-cell conjugates formed during priming events need to dissolve. Although detailed knowledge on molecules involved in the conjugate formation is available, dissolving of them has not been considered to be an active process. Here, we identify CYTIP (cytohesin-interacting protein) to mediate DC-T-cell deattachment. CYTIP, which is induced during maturation of DCs, shortly accumulates to the contact zones with T cells within the first hour of coculture. Specific silencing of CYTIP results in stronger adhesion of DCs to T cells and to fibronectin. When a need for deattachment is created in a T-cell priming assay by only partially loading DCs with antigen, CYTIP silencing causes reduced priming capacity. Thus, CYTIP allows DCs to actively control DC-T-cell interactions.

Antigen Presentation↗

PubMed2005

Tetrahydro-4-aminobiopterin attenuates dendritic cell-induced T cell priming independently from inducible nitric oxide synthase.

Formation of NO by NO synthases (NOSs) strictly depends on tetrahydrobiopterin. Its structural analog, tetrahydro-4-aminobiopterin, is an inhibitor of all NOS isoenzymes, which prolongs allograft survival in acute murine cardiac rejection and prevents septic shock in the rat. In this study, we show that murine bone marrow-derived dendritic cells treated with tetrahydro-4-aminobiopterin had a reduced capacity to prime alloreactive murine T cells in oxidative mitogenesis. Checking for a possible influence on LPS-induced dendritic cell maturation, we found that tetrahydro-4-aminobiopterin down-regulated MHC class II expression and counteracted LPS-induced down-regulation of ICOS ligand, while expression of CD40, CD86, CD80, B7-H1, and B7-DC remained unchanged. Tetrahydro-4-aminobiopterin also reduced activation of CD4(+) T cells isolated from mice overexpressing an OVA-specific TCR by OVA-loaded murine bone marrow-derived dendritic cells, thus indicating that its effect on MHC class II expression is involved in attenuating T cell activation. In line with affecting dendritic cell function and T cell activation, tetrahydro-4-aminobiopterin impaired production of proinflammatory cytokines and the Th1 response. With regard to cell survival, tetrahydro-4-aminobiopterin induced efficient apoptosis of murine T cells but not of murine dendritic cells. Experiments with cells from inducible NOS (iNOS) knockout mice and with N(6)-(1-iminoethyl)-L-lysine, a specific inhibitor of iNOS, ruled out participation of iNOS in any of the observed effects. These findings characterize attenuation of T cell stimulatory capacity of murine bone marrow-derived dendritic cells as an immunosuppressive mechanism of tetrahydro-4-aminobiopterin that is not related to its iNOS-inhibiting properties.

Animals↗

PubMed2005

The immunomodulator FTY720 interferes with effector functions of human monocyte-derived dendritic cells.

The potent immunomodulator FTY720 elicits immunosuppression via acting on sphingosine 1-phosphate receptors (S1PR), thereby leading to an entrapment of lymphocytes in the secondary lymphoid tissue. To elucidate the potential in vitro effects of this drug on human monocyte-derived DC, we used low nanomolar therapeutic concentrations of FTY720 and phosphorylated FTY720 (FTY720-P) and investigated their influence on DC surface marker expression, protein levels of S1PR and DC effector functions: antigen uptake, chemotaxis, cytokine production, allostimulatory and Th-priming capacity. We report that both FTY720 and FTY720-P reduce chemotaxis of immature and mature DC. Mature DC generated in the presence of FTY720 or FTY720-P showed an impaired immunostimmulatory capacity and reduced IL-12 but increased IL-10 production. T cells cultured in the presence of FTY720- or FTY720-P-treated DC showed an altered cytokine production profile indicating a shift from Th1 toward Th2 differentiation. In treated immature and mature DC, expression levels for two S1PR proteins, S1P1 and S1P4, were reduced. We conclude that in vitro treatment with FTY720 affects DC features that are essential for serving their role as antigen-presenting cells. This might represent a new aspect of the overall immunosuppressive action of FTY720 and makes DC potential targets of further sphingolipid-derived drugs.

Actins↗

PubMed2005

Langerhans cells are strongly reduced in the skin of transgenic mice overexpressing follistatin in the epidermis.

Activins are members of the transforming growth factor-beta (TGF-beta) family and are important for skin morphogenesis and wound healing. TGF-beta1 is necessary for the population of the epidermis with Langerhans cells (LC). However, a role for activin in LC biology is not known. To address this question, we analyzed skin from transgenic mice overexpressing the activin antagonist follistatin in the epidermis. Using immunofluorescence, we observed a striking decrease in the number of LC in the epidermis of transgenic mice in comparison to wild-type mice. Nevertheless, these LC expressed normal levels of major histocompatibility complex (MHC)-class II and Langerin/ CD207 in situ. In explant cultures of whole ear skin the number of dendritic cells (DC), which migrated into the culture medium, was reduced. This reduction was even more pronounced in cultures of epidermal sheets. Virtually all emigrated cutaneous DC displayed typical morphology with cytoplasmic "veils", showed translocation of MHC-class II to the surface membrane, and expressed the maturation marker 2A1. Thus, cutaneous DC from transgenic mice seemed to mature normally. These results demonstrate that overexpression of follistatin in the epidermis affects LC trafficking but not maturation and suggest a novel role of the follistatin-binding partner activin in LC biology.

Activins↗

PubMed2004

In vitro treatment of dendritic cells with tacrolimus: impaired T-cell activation and IP-10 expression.

BACKGROUND: High doses (10(-6)-10(-8) M) of tacrolimus (FK506) were reported to induce a type-2 T-helper cell (Th2)-promoting function in developing dendritic cells (DC). We used a therapeutic dose (2.4 x 10(-9 )M) of tacrolimus to investigate its effect on human monocyte-derived DC. METHODS: Using untreated and treated immature and mature DC we compared T cell-activating capacity, surface marker expression, T cell and DC cytokine profile and transcription of genes coding for a panel of DC function-related molecules. RESULTS: Tacrolimus-treated mature DC had reduced T-cell stimulatory capacity. Although interleukin (IL)-12 production of DC was impaired, they did not promote Th2 development as T cells activated by tacrolimus-treated DC produced less interferon (IFN)-gamma, IL-4 and IL-10. The up-regulation of the T-cell activation marker CD69 and the production of IL-2 were impaired. In addition, tacrolimus-treated DC produced less IP-10 (CXCL10), which is known to be involved in allograft rejection. Other molecules related to DC function remained unchanged. CONCLUSIONS: Tacrolimus treatment reduces the ability of DC to stimulate T cells and the impaired production of DC-derived IP-10 (CXCL10) and IL-12 might play a role in the immunosuppressive action of tacrolimus.

Cell Culture Techniques↗

PubMed2003

Low tetrahydrobiopterin biosynthetic capacity of human monocytes is caused by exon skipping in 6-pyruvoyl tetrahydropterin synthase.

Biosynthesis of (6 R )-5,6,7,8-tetrahydro-L-biopterin (H(4)-biopterin), an essential cofactor for aromatic amino acid hydroxylases and NO synthases, is effectively induced by cytokines in most of the cell types. However, human monocytes/macrophages form only a little H(4)-biopterin, but release neopterin/7,8-dihydroneopterin instead. Whereas 6-pyruvoyl tetrahydropterin synthase (PTPS) activity, the second enzyme of H(4)-biopterin biosynthesis, is hardly detectable in these cells, PTPS mRNA levels were comparable with those of cell types containing intact PTPS activity. By screening a THP-1 cDNA library, we identified clones encoding the entire open reading frame (642 bp) as well as clones lacking the 23 bp exon 3, which results in a premature stop codon. Quantification of the two mRNA species in different cell types (blood-derived cells, fibroblasts and endothelial cells) and cell lines showed that the amount of exon-3-containing mRNA is correlated closely to PTPS activity. The ratio of exon-3-containing to exon-3-lacking PTPS mRNA is not affected by differential mRNA stability or nonsense-mediated mRNA decay. THP-1 cells transduced with wild-type PTPS cDNA produced H(4)-biopterin levels and expressed PTPS activities and protein amounts comparable with those of fibroblasts. We therefore conclude that exon 3 skipping in transcription rather than post-transcriptional mechanisms is a major cause of the low PTPS protein expression observed in human macrophages and related cell types.

Base Sequence↗

PubMed2003

Attenuation of cell adhesion in lymphocytes is regulated by CYTIP, a protein which mediates signal complex sequestration.

An important theme in molecular cell biology is the regulation of protein recruitment to the plasma membrane. Fundamental biological processes such as proliferation, differentiation or leukocyte functions are initiated and controlled through the reversible binding of signaling proteins to phosphorylated membrane components. This is mediated by specialized interaction modules, such as SH2 and PH domains. Cytohesin-1 is an intracellular guanine nucleotide exchange factor, which regulates leukocyte adhesion. The activity of cytohesin-1 is controlled by phospho inositide-dependent membrane recruitment. An interacting protein was identified, the expression of which is upregulated by cytokines in hematopoietic cells. This molecule, CYTIP, is also recruited to the cell cortex by integrin signaling via its PDZ domain. However, stimulation of Jurkat cells with phorbol ester results in re-localization of CYTIP to the cytoplasm, and membrane detachment of cytohesin-1 strictly requires co-expression of CYTIP. Consequently, stimulated adhesion of Jurkat cells to intracellular adhesion molecule-1 is repressed by CYTIP. These findings outline a novel mechanism of signal chain abrogation through sequestration of a limiting component by specific protein-protein interactions.

Adenosine Triphosphate↗

PubMed2003

Adenosine slows migration of dendritic cells but does not affect other aspects of dendritic cell maturation.

We report the induction and reduction of adenosine receptor A2a and A3 mRNAs, respectively, during maturation of human monocyte-derived dendritic cells. Adenosine, an immunomodulatory molecule, is unstable in vitro; therefore we tested a stable agonist, 5'-(N-ethylcarboxamido)-adenosine, to explore the effect of adenosine receptor activation on dendritic cell function. We clearly show that adenosine receptor engagement affects the migratory activity of dendritic cells in three distinct settings. In human skin explant culture experiments the emigration of epidermal and dermal dendritic cells was diminished by the addition of 5'-(N-ethylcarboxamido)-adenosine. In a murine contact hypersensitivity assay 5'-(N-ethylcarboxamido)-adenosine caused a reduction in the numbers of epidermal and dermal dendritic cells arriving in the draining lymph node. In a chemotaxis assay of human dendritic cells in response to macrophage inflammatory protein 3beta (MIP-3beta)/CCL19, adenosine caused a delay in transmigration. Expression of a number of molecules involved in dendritic cell migration (CCR5, MIP-3beta/CCL19, and MDR-1) was reduced. Importantly, all other features of dendritic cells tested--phenotype, antigen uptake, cytokine production, T cell activation, and the T cell subset induction--remained unchanged. Dendritic cells carry antigens from the periphery to secondary lymphoid organs, where initiation of immune responses occurs. Increased adenosine release may modulate immune responses by delaying the encounter of antigen-loaded dendritic cells with T cells.

Adenosine↗

PubMed2002

A novel role for IL-3: human monocytes cultured in the presence of IL-3 and IL-4 differentiate into dendritic cells that produce less IL-12 and shift Th cell responses toward a Th2 cytokine pattern.

Dendritic cells (DC) derived from plasmacytoid precursors depend on IL-3 for survival and proliferation in culture, and they induce preferentially Th2 responses. Monocytes express not only GM-CSF receptors, but also IL-3Rs. Therefore, we examined whether IL-3 had an effect on the functional plasticity of human monocyte-derived DC generated in a cell culture system that is widely used in immunotherapy. DC were generated with IL-3 (instead of GM-CSF) and IL-4. Yields, maturation, phenotype (surface markers and Toll-like receptors), morphology, and immunostimulatory capacity were similar. Only CD1a was differentially expressed, being absent on IL-3-treated DC. In response to CD40 ligation DC generated in the presence of IL-3 secreted significantly less IL-12 p70 and more IL-10 compared with DC grown with GM-CSF. Coculture of naive allogeneic CD4(+) T cells with DC generated in the presence of IL-3 induced T cells to produce significantly more IL-5 and IL-4 and less IFN-gamma compared with stimulation with DC generated with GM-CSF. These data extend the evidence that different cytokine environments during differentiation of monocyte-derived DC can modify their Th cell-inducing properties. A hitherto unrecognized effect of IL-3 on DC was defined, namely suppression of IL-12 secretion and a resulting shift from Th1 toward Th2.

Adjuvants, Immunologic↗