Biomedical subjects

Andreas Thiel

Publications and source records attributed to Andreas Thiel.

23 records · Page 2Linked to original sources

PubMed2004

The IkappaB kinase complex and NF-kappaB act as master regulators of lipopolysaccharide-induced gene expression and control subordinate activation of AP-1.

Toll-like receptors (TLRs) recognize conserved products of microbial pathogens to initiate the innate immune response. TLR4 signaling is triggered upon binding of lipopolysaccharides (LPS) from gram-negative bacteria. Using comparative gene expression profiling, we demonstrate a master regulatory role of IkappaB kinase (IKK)/NF-kappaB signaling for immediate-early gene induction after LPS engagement in precursor B cells. IKK/NF-kappaB signaling controls a large panel of gene products associated with signaling and transcriptional activation and repression. Intriguingly, the induction of AP-1 activity by LPS in precursor B cells and primary dendritic cells fully depends on the IKK/NF-kappaB pathway, which promotes expression of several AP-1 family members, including JunB, JunD, and B-ATF. In pre-B cells, AP-1 augments induction of a subset of primary NF-kappaB targets, as shown for chemokine receptor 7 (CCR7) and immunoglobulin kappa light chain. Thus, our data illustrate that NF-kappaB orchestrates immediate-early effects of LPS signaling and controls secondary AP-1 activation to mount an appropriate biological response.

B-Lymphocytes↗

PubMed2003

Substitution in position 3 of cyclosporin A abolishes the cyclophilin-mediated gain-of-function mechanism but not immunosuppression.

Binary complex formation between the immunosuppressive drug cyclosporin A (CsA) and cyclophilin 18 is the prerequisite for the ability of CsA to inhibit the protein phosphatase activity of calcineurin, a central mediator of antigen-receptor signaling. We show here that several CsA derivatives substituted in position 3 can inhibit calcineurin without prior formation of a complex with cyclophilin 18. [Methylsarcosine(3)]CsA was shown to inhibit calcineurin, either in its free form with an IC(50) value of 10 microm, or in its complex form with cyclophilin 18 with an IC(50) of 500 nm. [Dimethylaminoethylthiosarcosine(3)]CsA ([Dat-Sar(3)]CsA) was found to inhibit calcineurin on its own, with an IC(50) value of 1.0 microm, but was not able to inhibit calcineurin after forming the [Dat-Sar(3)]CsA-cyclophilin 18 binary complex. Despite their different inhibitory properties, both CsA and [Dat-Sar(3)]CsA suppressed T cell proliferation and cytokine production mainly through blocking NFAT activation and interleukin-2 gene expression. Furthermore, to demonstrate that [Dat-Sar(3)]CsA can inhibit calcineurin in a cyclophilin-independent manner in vivo, we tested its effect in a Saccharomyces cerevisiae strain (Delta12), in which all the 12 cyclophilins and FKBPs were deleted. [Dat-Sar(3)]CsA, but not CsA, bypassed the requirement for cellular cyclophilins and caused growth inhibition in the salt-stressed Delta12 strain.

Amino Acid Substitution↗

PubMed2003

Down-regulation of the nonspecific and antigen-specific T cell cytokine response in ankylosing spondylitis during treatment with infliximab.

OBJECTIVE: Treatment of active ankylosing spondylitis (AS) with the monoclonal tumor necrosis factor alpha (TNF alpha) antibody infliximab is highly clinically effective. This study was undertaken to investigate the precise mechanism of action of anti-TNF alpha treatment in AS. METHODS: Cytokine expression of CD4+ and CD8+ T cells was investigated before and 6 and 12 weeks after the start of treatment in 10 patients treated with infliximab, and before and after 6 weeks of treatment and 6 weeks after placebo was switched to infliximab in 10 patients treated initially with placebo. Peripheral blood mononuclear cells (PBMCs) were stimulated for 6 hours either nonspecifically with phorbol myristate acetate (PMA)/ionomycin or antigen specifically with a pool of 46 overlapping 18-mer peptides derived from the G1 domain of aggrecan. Cells were stained for T cell surface markers CD4 and CD8 and for the intracellular cytokines interferon-gamma (IFN gamma), TNF alpha, interleukin-4 (IL-4), and IL-10. Positive cells were quantified by flow cytometry. For monocyte-derived cytokines, PBMCs were stimulated with lipopolysaccharide (LPS) for 18 hours and TNF alpha and IL-10 in the supernatant were measured by enzyme-linked immunosorbent assay. RESULTS: Compared with baseline, infliximab treatment induced a significant decrease at 12 weeks in the number of CD4+ and CD8+ T cells that were positive for IFN gamma and TNF alpha upon PMA/ionomycin stimulation (P = 0.005). A significant reduction had already begun to occur at 6 weeks. No change in the percent IFN gamma or TNF alpha positivity among CD4+ and CD8+ subpopulations was observed after 6 weeks in patients treated with placebo. However, when these patients began infliximab treatment after 6 weeks of receiving placebo, there was a similar significant decrease in IFN gamma and TNF alpha production by CD4+ and CD8+ T cells (P < 0.05). Furthermore, infliximab treatment induced a significant reduction in the number of IFN gamma+ and TNF alpha+ CD8+ T cells (P = 0.005 at week 6 and week 12) after antigen-specific in vitro stimulation with G1-derived peptides. Between-group analysis showed that the change in the expression of IFN gamma and TNF alpha in both CD4+ and CD8+ T cells was significantly different between the infliximab and placebo groups (P = 0.001 for all variables). There was no change in the number of IL-10+ or IL-4+ T cells during treatment. No significant change in the production of TNFalpha and IL-10 upon in vitro stimulation of PBMCs with LPS was detectable during infliximab treatment. CONCLUSION: Infliximab down-regulates both IFN gamma and TNF alpha secreted by T cells but does not induce a change in cytokines produced by monocytes during 3 months of treatment. This is likely to be a relevant mechanism for the clinical efficacy of this therapy.

Antibodies, Monoclonal↗

PubMed2002

Two subsets of naive T helper cells with distinct T cell receptor excision circle content in human adult peripheral blood.

During ageing thymic function declines and is unable to meet the demand for peripheral T helper (Th) cell replenishment. Therefore, population maintenance of naive Th cells must be at least partly peripherally based. Such peripheral postthymic expansion of recent thymic emigrants (RTEs) during ageing consequently should lead to loss or dilution of T cell receptor excision circles (TRECs) from a subset of naive T cells. We have identified two subsets of naive Th cells in human adult peripheral blood characterized by a striking unequal content of TRECs, indicating different peripheral proliferative histories. TRECs are highly enriched in peripheral naive CD45RA(+) Th cells coexpressing CD31 compared with peripheral naive CD45RA(+) Th cells lacking CD31 expression, in which TRECs can hardly be detected. Furthermore we show that CD31(-)CD45RA(+) Th cells account for increasing percentages of the naive peripheral Th cell pool during ageing but retain phenotypic and functional features of naive Th cells. As CD31 is lost upon T cell receptor (TCR) engagement in vitro, we hypothesize that TCR triggering is a prerequisite for homeostatically driven peripheral postthymic expansion of human naive RTEs. We describe here the identification of peripherally expanded naive Th cells in human adult blood characterized by the loss of CD31 expression and a highly reduced TREC content.

Adult↗

PubMed2002

Simultaneous cytometric analysis of (auto)antigen-reactive T and B cell proliferation.

The detection and characterization of (auto)antigen-specific lymphocytes, both B and T cells, is essential to investigate immunopathologic mechanisms. Our aim was to perform a CFSE (Carboxyfluorescein diacetate succinimidyl ester)-based cytometric analysis of peripheral blood mononuclear cells (PBMC) proliferating in response to antigenic provocation. CFSE-labeled PBMC were stimulated with a superantigen (SEB), a recall antigen (tetanus toxoid), an allergen (grass pollen) and an autoantigen (nucleosomes) and stained after cultivation with CD4-, CD8- and CD19-antibodies. Proliferated cells were identified cytometrically by the decrease of the CFSE fluorescence intensity due to cell division. Antigen-reactive, proliferated B cells were further analysed phenotypically, antigen-specific proliferated Th cells were further characterized functionally regarding their cytokine secretion pattern after polyclonal restimulation. Using this technique, antigen-specific proliferated B and Th cells were detected even at low frequencies. Analyzing the cytokine secretion pattern of allergen-reactive proliferated Th cells after polyclonal restimulation we found differences in the expression of IL-13 and IL-4 between an atopic and a healthy donor. After stimulation of PBMC from TT-vaccinated donors TT-specific proliferated B cells were detected in high frequencies and showed a plasmablast-typical CD20(low) CD27(high) phenotype with only low frequencies expressing CD138 (= Syndecan-1). Proliferation of nucleosome-reactive Th cells and B cells was observed in both patients and healthy controls. We have optimized here the cytometric analysis of reactive cell proliferation based on CFSE offering various facilities of application on the further characterization of both antigen-specific B and T cells.

Antigens, Bacterial↗