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Andreas Radbruch

Publications and source records attributed to Andreas Radbruch.

54 records · Page 3Linked to original sources
PubMed2003

Plasma cell survival is mediated by synergistic effects of cytokines and adhesion-dependent signals.

Recent results suggest that plasma cell longevity is not an intrinsic capacity, but depends on yet unknown factors produced in their environment. In this study, we show that the cytokines IL-5, IL-6, TNF-alpha, and stromal cell-derived factor-1alpha as well as signaling via CD44 support the survival of isolated bone marrow plasma cells. The cytokines IL-7 and stem cell factor, crucially important for early B cell development, do not mediate plasma cell survival, indicating that plasma cells and early B cells have different survival requirements. As shown in IL-6-deficient mice, IL-6 is required for a normal induction, but not for the maintenance of plasma cell responses in vivo, indicating that the effects of individual survival factors are redundant. Optimal survival of isolated plasma cells requires stimulation by a combination of factors acting synergistically. These results strongly support the concept that plasma cell survival depends on niches in which a combination of specific signals, including IL-5, IL-6, stromal cell-derived factor-1alpha, TNF-alpha, and ligands for CD44, provides an environment required to mediate plasma cell longevity.

Animals↗
PubMed2003

Monoclonal anti-equine IgE antibodies with specificity for different epitopes on the immunoglobulin heavy chain of native IgE.

In this study we describe the generation of monoclonal antibodies (mAbs), which recognize different epitopes of the equine IgE constant heavy chain. Equi-murine recombinant IgE (rIgE), composed of the murine V(H)186.2 heavy chain variable region, linked to the equine IgE constant heavy chain and expressed together with the murine lambda(1) chain in J558L cells was used to immunize BALB/C mice. A total of 17 different mAbs were obtained, which recognized the rIgE heavy chain constant region. None of the mAbs reacted with monoclonal equine isotypes IgM, IgG1 (IgGa), IgG3 (IgG(T)), IgG4 (IgGb) or isolated equine light chains, IgGc and IgA from horse serum, or the native mAb B1-8delta, expressing the same heavy chain variable regions and light chains. One of the mAbs (alphaIgE-132) recognized the recombinant equine IgE, but did not recognize any protein in equine serum, i.e. native IgE. A total of 16 mAbs detected a serum protein of approximately 210,000Da on Western blots, corresponding to the expected MW of native IgE. In addition, one of the mAbs (alphaIgE-176) detected a protein of 76,000Da under reducing conditions, most likely the equine IgE heavy chain. According to binding inhibition studies, the equine IgE specific mAbs recognize at least two different epitopes of the equine IgE. In an ELISA using two anti-IgE mAbs which recognized different epitopes, no significant differences in the concentration of total serum IgE could be detected between adult Icelandic horses with IgE-mediated type I allergy (summer eczema) and healthy control animals. In Icelandic horse foals, no serum IgE could be measured 6 months post partum. All anti-IgE mAbs recognized a small population (1.3+/-0.5%) of leukocytes from adult Icelandic horses by surface immunofluorescence, but no cells could be detected in foal blood. The stained leukocytes from adult horses could be enriched by magnetic cell sorting and contained 32% basophils, 53% monocytes and/or large lymphocytes, 13% small lymphocytes and 2% eosinophils.

Animals↗
PubMed2003

Expression of ICOS in vivo defines CD4+ effector T cells with high inflammatory potential and a strong bias for secretion of interleukin 10.

The studies performed to date analyzed the overall participation of the inducible costimulator (ICOS) in model diseases, but did not yield information on the nature and function of ICOS-expressing T cells in vivo. We examined ICOS(+) T cells in the secondary lymphoid organs of nonmanipulated mice, in the context of an "unbiased" immune system shaped by environmental antigens. Using single cell analysis, ICOS(low) cells were found to be loosely associated with the early cytokines interleukin (IL)-2, IL-3, IL-6, and interferon (IFN)-gamma. ICOS(medium) cells, the large majority of ICOS(+) T cells in vivo, were very tightly associated with the synthesis of the T helper type 2 (Th2) cytokines IL-4, IL-5, and IL-13, and these cells exhibited potent inflammatory effects in vivo. In contrast, ICOS(high) T cells were highly and selectively linked to the anti-inflammatory cytokine IL-10. Overall, these data seem to indicate that ICOS cell surface density serves as a regulatory mechanism for the release of cytokines with different immunological properties. Further in vivo functional experiments with in vitro-activated T cells strongly suggested that the ICOS(+) population, although representing in vivo only around 10% of T cells bearing early or late activation markers, nevertheless encompasses virtually all effector T cells, a finding with major diagnostic and therapeutic implications.

Adoptive Transfer↗
PubMed2003

Identification and characterization of SmD183-119-reactive T cells that provide T cell help for pathogenic anti-double-stranded DNA antibodies.

OBJECTIVE: The C-terminal peptide of amino acids 83-119 of the SmD1 protein is a target of the autoimmune response in human and murine lupus. This study was undertaken to test the hypothesis that SmD1(83-119)-reactive T cells play a crucial role in the generation of pathogenic anti-double-stranded DNA (anti-dsDNA) antibodies. METHODS: Splenic or lymph node T cells derived from unmanipulated as well as SmD1(83-119)-immunized NZB/NZW mice were analyzed in vitro by enzyme-linked immunospot (ELISpot) assay to determine T cell help for anti-dsDNA generation induced by the SmD1(83-119) peptide. Cytokines expressed by these T cells were measured by ELISpot assay, enzyme-linked immunosorbent assay, and flow cytometry. SmD1(83-119)- and ovalbumin-specific T cell lines were generated and characterized. RESULTS: The SmD1(83-119) peptide, but not the control peptides, significantly increased the in vitro generation of anti-dsDNA antibodies in cultures from unmanipulated NZB/NZW mice. Interferon-gamma (IFNgamma), interleukin-2 (IL-2), IL-4, transforming growth factor beta, and IL-10 production increased in response to the peptide in young mice; only IFNgamma and IL-2 were increased in older, diseased mice. Activation of SmD1(83-119)-reactive T cells by immunization of NZB/NZW mice resulted in elevated anti-dsDNA synthesis and, later, increased antibodies to SmD1(83-119). Most cells in SmD1(83-119)-specific CD4+ T cell lines helping both antibodies had increased intracellular expression of IFNgamma, and most expressed both IFNgamma and IL-4. CONCLUSION: The SmD1(83-119) peptide plays an important role in generating T cell help for autoantibodies, including anti-dsDNA, and activates different subsets of T cells as defined by distinct cytokine expression. This peptide is an interesting target structure for the modulation of autoreactive T cells, and its characterization may contribute to our understanding of the role of autoantigen-reactive T cells in the pathogenesis of SLE.

Animals↗
PubMed2003

Correlation between circulating CD27high plasma cells and disease activity in patients with systemic lupus erythematosus.

OBJECTIVE: Disease activity in systemic lupus erythematosus (SLE) is usually assessed with complex disease activity scores comprising a variety of different parameters. In order to determine whether SLE disease activity correlates with abnormal B lymphocyte activity, B cell subsets were analyzed, and their relationship to clinical and humoral measures of disease activity was assessed. METHODS: The distribution of B cell subsets was determined by fluorescence-activated cell sorting analysis and assessed in relation to the autoantibody profile, disease activity measured by the SLE Disease Activity Index (SLEDAI) and the European Consensus Lupus Activity Measure scores, disease duration, and therapy. RESULTS: The number and frequency of CD27(high) plasma cells were significantly correlated with the SLE disease activity indices and with the titer of anti-double-stranded DNA (anti-dsDNA) autoantibodies. Circulating B cell subsets were not influenced by age or sex, but appeared to relate to the duration of disease and the therapeutic regimen, with the number and frequency of CD27(high) plasma cells increasing and those of CD27- naive B cells decreasing over time. Patients were divided into those with a SLEDAI score of 0-8 (low disease activity) and those with SLEDAI score >8 (high disease activity). Patients with high disease activity had an increased frequency of both CD19+ B cells and CD27(high) plasma cells. By using a nonparametric data sieving algorithm, we observed that these B cell abnormalities provided predictive values for nonactive and active disease of 78.0% and 78.9%, respectively. The predictive value of the B cell abnormalities (78.9%) was greater than that of the humoral/clinical data pattern (71.4%), including anti-dsDNA antibody levels, circulating immune complexes, increased erythrocyte sedimentation rate, mucocutaneous involvement, and acute renal involvement. CONCLUSION: Flow cytometric monitoring of B cell subsets in the peripheral blood provides new insights into abnormalities of B cell function in SLE and may also be a diagnostically valuable option for monitoring the activity of this autoimmune disease.

Adult↗
PubMed2003

Sensitive visualization of peptide presentation in vitro and ex vivo.

BACKGROUND: The presentation of antigenic peptides to specific T cells is one of the key events for the induction of a T-cell-dependent immune response. The nature of the antigen-presenting cells which present distinct peptides has been difficult to analyze so far due to the low number of peptides presented in vivo by a single antigen-presenting cell. METHODS: We have used magnetofluorescent liposomes to identify and characterize antigen-presenting cells according to presentation of a hapten-labeled antigenic peptide in vitro and ex vivo. RESULTS: Magnetofluorescent liposomes allowed the identification and isolation of antigen-presenting cells according to the presentation of less than 100 peptides per cell, the physiological threshold for activation of specific T cells. Ex vivo, we could demonstrate peptide presentation by B lymphocytes and dendritic cells already 1 h after intravenous peptide injection; this rapidly declined to background level after 12-24 h. CONCLUSIONS: The sensitive visualization of peptide presentation allows the phenotypical and functional characterization of those antigen-presenting cells which present specific peptides at physiological relevant quantities. This technology will help to characterize the antigen-presenting cells (APC) which are responsible for the induction of distinct immune reactions in vivo, e.g., the generation of tolerance or immunity.

Animals↗
PubMed2003

Visualization of peptide presentation following oral application of antigen in normal and Peyer's patches-deficient mice.

Orally applied antigens generate systemic unresponsiveness by induction of anergy and deletion of specific T cells at high antigen doses, and induction of regulatory T cells at low doses of antigen. These different immune reactions have been attributed to different types of antigen-presenting cells (APC) and/or different secondary lymphoid organs participating in the induction of the immune response. We used high-sensitivity immunofluorescence to directly identify for the first time the cells presenting orally applied antigen in vivo. At low peptide doses (<1 mg) peptide presentation was exclusively detected on dendritic cells (DC) of the Peyer's patches (PP) and mesenteric lymph nodes (mLN). At high doses (>1 mg) peptides were presented systemically and by all types of APC but presentation was still maximal on DC of the PP (up to 65%). Nevertheless, at limiting antigen doses T cell activation in the gut-associated lymphoid tissue occurs preferentially in the mLN but not in PP. PP-deficient mice have the same frequencies of peptide-presenting cells in mLN, peripheral lymph nodes and spleen and activation of naive T cells in vivo is not affected. Therefore, PP are not critical for antigen presentation as well as for T cell activation in response to orally applied soluble antigens.

Administration, Oral↗
PubMed2002

Chemotactic responsiveness toward ligands for CXCR3 and CXCR4 is regulated on plasma blasts during the time course of a memory immune response.

Plasma blasts formed during memory immune responses emigrate from the spleen to migrate into the bone marrow and into chronically inflamed tissues where they differentiate into long-lived plasma cells. In this study, we analyze the chemokine responsiveness of plasma blasts formed after secondary immunization with OVA. Starting from day 4 and within approximately 48 h, OVA-specific plasma blasts emigrate from spleen and appear in the bone marrow. Although these migratory cells have lost their responsiveness to many B cell attracting chemokines, e.g., CXC chemokine ligand (CXCL)13 (B lymphocyte chemoattractant), they migrate toward CXCL12 (stromal cell-derived factor 1 alpha), and toward the inflammatory chemokines CXCL9 (monokine induced by IFN-gamma), CXCL10 (IFN-gamma-inducible protein 10), and CXCL11 (IFN-inducible T cell alpha chemoattractant). However, the responsiveness of plasma blasts to these chemokines is restricted to a few days after their emigration from the spleen, indicating a role for these molecules and their cognate receptors, i.e., CXCR3 and CXCR4, in the regulation of plasma blast migration into the bone marrow and/or inflamed tissues.

Animals↗
PubMed2002

Evolution of the six horse IGHG genes and corresponding immunoglobulin gamma heavy chains.

It is generally assumed that the different mammalian IgG isotypes have developed during evolution by duplications of a common ancestor gamma heavy chain constant region gene (IGHG). In contrast to other species studied so far, which express between one and four IGHG genes, the horse (Equus caballus) genome contains six IGHG genes, and it has been postulated that they all can be expressed. For determination of the evolutionary history of the six horse IGHG genes, genomic DNA and cDNA of the IGHG genes were sequenced. The structure of these genes with reference to exons and introns was determined. Comparison of the deduced amino acid sequences of the horse IGHG genes revealed the greatest divergences in the hinge regions, and in the proximal CH2 domains. A phylogenetic comparison of the amino acid sequences of the six horse IGHG genes to those of other species shows that the horse IGHG genes form a distinct cluster. This indicates that the mammalian species included in this study probably share only one common ancestor IGHG gene with the horse. The six horse IGHG genes probably then evolved by gene duplication after species separation. In addition, various segmental exchanges were found between the horse IGHG genes, which might be the result of unequal crossing over and/or gene conversion events during the evolution of the six horse IGHG genes.

Amino Acid Sequence↗
PubMed2002

GATA-3 transcriptional imprinting in Th2 lymphocytes: a mathematical model.

Immunological memory involves the fast recall of cytokine expression by T helper (Th) lymphocytes. Two distinct profiles of cytokine expression, Th1 and Th2, can be induced by antigen and polarizing signals during activation of naive Th cells and can subsequently be reexpressed on stimulation by antigen alone. The transcription factor GATA-3 induces Th2 development. GATA-3 is activated by the Th2-polarizing stimulus, IL-4, and has recently been observed to autoactivate its transcription. Based on these experimental data, we developed a mathematical model of GATA-3 expression that assumes independent activation of GATA-3 transcription by IL-4 and by GATA-3. Cooperativity of GATA-3 transcriptional activation is shown to create a threshold for autoactivation, resulting in the coexistence of two distinct GATA-3 expression states: a state of basal expression and a state of high expression sustained by autoactivation. Suprathreshold IL-4 signals induce a transition from basal to high GATA-3 expression. Thus, GATA-3 autoactivation creates a bistable system that can memorize a transient inductive signal. The model further predicts conditions under which the state of high GATA-3 expression can be abolished, which may extinguish the Th2 cytokine memory.

Animals↗
PubMed2002

MIP-1alpha, MIP-1beta, RANTES, and ATAC/lymphotactin function together with IFN-gamma as type 1 cytokines.

We analyzed for the first time the expression of chemokines in subpopulations of the murine immune system at the single-cell level. We demonstrate in vitro and in a model of murine listeriosis that macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, regulated on activation normal T cell expressed and secreted (RANTES), and activation-induced, T cell-derived, and chemokine-related cytokine (ATAC)/lymphotactin are cosecreted to a high degree with IFN-gamma by activated individual natural killer (NK), CD8(+) T, and CD4(+) T helper 1 (Th1) cells. Functionally, ATAC and the CC chemokines cooperate with IFN-gamma in the up-regulation of CD40, IL-12, and tumor necrosis factor-alpha, molecules playing a central role in the effector phase of macrophages. Our data indicate that (i) MIP-1alpha, MIP-1beta, RANTES, and ATAC are not only chemoattractants but also coactivators of macrophages, (ii) MIP-1alpha, MIP-1beta, RANTES, and ATAC constitute together with IFN-gamma a group of "type 1 cytokines," and (iii) these cytokines act together as a functional unit that is used by NK cells in the innate phase and then "handed over" to CD8(+) T cells in the antigen-specific phase of the immune defense, thus bridging the two components of a Th1 immune reaction.

Animals↗
PubMed2002

Differential surrogate light chain expression governs B-cell differentiation.

Surrogate light chain expression during B lineage differentiation was examined by using indicator fluorochrome-filled liposomes in an enhanced immunofluorescence assay. Pro-B cells bearing surrogate light chain components were found in mice, but not in humans. A limited subpopulation of relatively large pre-B cells in both species expressed pre-B cell receptors. These cells had reduced expression of the recombinase activating genes, RAG-1 and RAG-2. Their receptor-negative pre-B cell progeny were relatively small, expressed RAG-1 and RAG-2, and exhibited selective down-regulation of VpreB and lambda5 expression. Comparative analysis of the 2 pre-B cell subpopulations indicated that loss of the pre-B cell receptors from surrogate light chain gene silencing was linked with exit from the cell cycle and light chain gene rearrangement to achieve B-cell differentiation.

Animals↗
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

Plasma cells for a lifetime?

Antigen-specific serum antibodies are protective for long periods of time 1, 2. These serum antibodies, the "humoral memory", are secreted by plasma cells derived from activated, antigen-specific B lymphocytes. Given their crucial role in immunity, surprisingly little is known about the biology of plasma cells. One of the fundamental questions is whether persisting protective serum antibody responses are maintained by long-lived plasma cells, or by short-lived plasma cells generated continuously from activated memory B cells. Here, we review some recent experiments suggesting that plasma cells have the capacity to live for unlimited time if rescued by specific factors provided in a limited number of survival niches in the body.

Animals↗
PubMed2002

Cytokine memory of T helper lymphocytes.

Memory is one of the key features of the adaptive immune system. Specific T and B lymphocytes are primed for a particular antigen and upon challenge with it will react faster than naive lymphocytes. They also memorize the expression of key effector molecules, in particular cytokines, which determine the type and scale of an immune reaction. While in primary activations differential expression of cytokine genes is dependent on antigen-receptor signaling and differentiation signals, in later activations the expression is triggered by antigen-receptor signaling and dependent on the cytokine memory. The molecular basis of the cytokine memory implies differential expression of transcription factors and epigenetic modifications of cytokine genes and gene loci. GATA-3 for Th2 and T-bet for Th1 cells expressing interleukin-4 or interferon-gamma, respectively, are prime candidates for key transcription factors of cytokine memory. The essential role of epigenetic modifications is suggested by the requirement of DNA synthesis for the establishment of a cytokine memory in Th lymphocytes. At present the molecular link between transcription factors and epigenetic modifications of cytokine genes in the establishment and maintenance of cytokine memory is not clear. The initial cytokine memory is not stable against adverse differentiation signals, while in repeatedly stimulated lymphocytes it is stabilized by a variety of mechanisms.

Animals↗
PubMed2002

Humoral immunity and long-lived plasma cells.

A selected fraction of plasmablasts enters the compartment of nondividing, long-lived plasma cells to maintain humoral antibody memory. In accord with a current model for lymphocyte homeostasis, the lifetime of long-lived plasma cells is probably regulated by competition for a limited number of survival niches present in splenic red pulp, bone marrow and inflamed tissue. Plasma cells secreting autoantibodies specific for some, but not all, self-antigens are probably 'allowed' to enter the compartment of long-lived plasma cells and provide antibody-mediated 'autoimmune memory' that is resistant to conventional therapies.

Animals↗
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↗