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Georg Stingl

Publications and source records attributed to Georg Stingl.

At least 37 records · Page 2Linked to original sources
PubMed2004

Lipid raft-associated GTPase signaling controls morphology and CD8+ T cell stimulatory capacity of human dendritic cells.

Their eponymous morphology and unique ability to activate naive T cells are hallmark features of dendritic cells (DCs). Specific properties of the actin cytoskeleton may define both characteristics. In search for regulators that coordinate DC phenotype and function, we observed strongly increased expression of the actin-remodeling GTPases Cdc42 and Rac1 during DC development from human stem cells. Cdc42 and Rac1 are constitutively active in immature DCs, and their activity is further up-regulated by maturational stimuli such as LPS or CD40L. Activation of Rac1 is associated with its rapid recruitment into lipid rafts. Cdc42 is not recruited into rafts, but readily activated by raft-associated moieties. The functional interplay of rafts, GTPases, and cortical actin is further shown by GTPase activation and actin remodeling after pharmacological disruption of lipid rafts and by the loss of the actin-based DC morphology by transfection of dominant-negative Cdc42 and Rac1. Both Cdc42 and Rac1 also control the transport of essential immunostimulatory molecules to the DC surface. Transfection with dominant-negative GTPases led to reduced surface expression of MHC class I and CD86. Consecutively, DCs display a reduced stimulatory capacity for CD8(+) T cells, whereas MHC class II-dependent stimulation of CD4(+) T cells remains unperturbed. We conclude that Cdc42 and Rac1 signaling controls DC morphology and conditions DCs for efficient CD8(+) T cell stimulation.

Actins↗
PubMed2004

Autocrine IL-10 partially prevents differentiation of neonatal dendritic epidermal leukocytes into Langerhans cells.

To test whether reduced immune responsiveness in early life may be related to the immaturity of neonatal antigen-presenting cells, we comparatively assessed the phenotypic and functional characteristics of dendritic epidermal leukocytes (DEL) and epidermal Langerhans cells (LC) in newborn (NB) and adult mice, respectively. We report that purified, 3-day-cultured DEL do not acquire the morphology and phenotype typical of LC and are significantly weaker stimulators of naive, allogeneic CD4+ and CD8+ T cells than LC. Freshly isolated DEL are twice as efficient as LC in the uptake of fluorescein isothiocyanate-conjugated tracers but are not able to present these to antigen-specific T cell hybridomas. To clarify the underlying cause, cytokine expression of NB and adult epidermal cells (EC) was examined. We found that DEL express considerable amounts of interleukin (IL)-10, that IL-10 in NB EC supernatants partially inhibits LC maturation, and that DEL-enriched EC from IL-10-/- mice induce stronger primary T cell responses compared with those from IL-10+/+ mice. We conclude that IL-10 is one of the factors preventing maturation and differentiation of DEL into immunocompetent LC in intrauterine life and is at least partly responsible for the poor immune responsiveness of neonates.

Age Factors↗
PubMed2004

Inhaled dexamethasone differentially attenuates disease relapse and established allergic asthma in mice.

Inhaled glucocorticoids are effective in patients with chronic allergic asthma. We examined the effects of inhaled glucocorticoids on relapse (allergen challenge after disease remission) and established/overt allergic asthma (repeated allergen challenge in weekly intervals) in mice to establish a reference standard for novel treatments. BALB/c mice were treated before relapse or during overt disease with 1 h of nebulized PBS or 10 mg% dexamethasone twice daily for 5 days. Dexamethasone eliminated airway hyperresponsiveness before relapse and during overt disease. They more efficiently reduced airway inflammation, mucus production, and OVA-specific IgG1 and IgE during relapse compared to overt disease. However, during overt disease, parenchymal inflammatory infiltrates were more effectively eliminated compared to relapse, suggesting that activated infiltrating leukocytes have increased sensitivity to steroids. These data demonstrate that inhaled corticosteroids attenuate relapse and overt disease differentially and suggest that both airway and parenchymal inflammation need to be evaluated for treatment efficacy.

Administration, Inhalation↗
PubMed2004

Corticosteroids but not pimecrolimus affect viability, maturation and immune function of murine epidermal Langerhans cells.

Given the importance of dendritic cells in the immune response, we investigated the effect of corticosteroids (CS) on the integrity, survival, and function of murine Langerhans cells (LC) in comparison with pimecrolimus, a novel anti-inflammatory drug for the topical treatment of atopic dermatitis. BALB/c mice were treated twice on one day with ethanolic solutions of the compounds. At 24-72 h after the last application, we observed fragmented DNA, caspase-3 activity, and an upregulation of CD95 expression in LC from mice treated with CS but not in LC of pimecrolimus- or vehicle-treated animals. CS-epidermal cell (EC) supernatants but not pimecrolimus-EC supernatants contained significantly lower amounts of soluble factors (GM-CSF, TNF-alpha, IL-1alpha) required for LC survival and maturation than EC supernatants from vehicle-treated mice. With regard to LC maturation, CS but not pimecrolimus inhibited the expression of CD25, CD205, and costimulatory molecules. In line with this, LC from pimecrolimus-treated mice were similar to LC from vehicle-treated mice in their capacity to stimulate antigen-presenting function and migration, whereas LC from CS-treated mice were greatly impaired in these abilities. In summary, our data show for the first time that CS but not pimecrolimus induce apoptosis in LC in situ, implying that the prolonged use of CS could have adverse effects on the skin immune system.

Administration, Topical↗
PubMed2004

CpG motifs are efficient adjuvants for DNA cancer vaccines.

DNA vaccines can induce impressive specific cellular immune response (IR) when taking advantage of their recognition as pathogen-associated molecular patterns (PAMP) through Toll-like receptors (TLR) expressed on/in cells of the innate immune system. Among the many types of PAMP, immunostimulatory DNA, so-called CpG motifs, was shown to interact specifically with TLR9, which is expressed in plasmacytoid dendritic cells (pDC), a key regulatory cell for the activation of innate and adaptive IR. We now report that CpG motifs, when introduced into the backbone, are a useful adjuvant for plasmid-based DNA (pDNA) vaccines to induce melanoma antigen-specific protective T cell responses in the Cloudman M3/DBA/2 model. The CpG-enriched pDNA vaccine induced protection against subsequent challenge with melanoma cells at significantly higher levels than its parental unmodified vector. Preferential induction of an antigen-specific, protective T cell response could be demonstrated by (i) induction of antigen-dependent tumor cell protection, (ii) complete loss of protection by in vivo CD4+/CD8+T cell- but not NK cell-depletion, and (iii) the detection of antigen-specific T cell responses but not of relevant NK cell activity in vitro. These results demonstrate that employing PAMP in pDNA vaccines improves the induction of protective, antigen-specific, T cell-mediated IR.

Adjuvants, Immunologic↗
PubMed2003

Repeated aerosol allergen exposure suppresses inflammation in B-cell-deficient mice with established allergic asthma.

BACKGROUND: Repeated allergen administration is a well-established therapeutic strategy for desensitizing patients with allergic disease. Similarly, repeated inhalation of antigen by mice with established allergen-induced asthma suppresses allergic inflammation. The mechanisms underlying antigen-dependent suppression of allergic immune responses remain unknown. In previous studies, we found that repeated aerosol antigen challenges in sensitized mice reduced eosinophils while increasing plasma cells and antibody in the lungs. We sought to test whether plasma cells and antibody played a role in suppression of allergic disease. METHODS: We primed wild-type and B-cell-deficient (microMT) mice with 25 microg ovalbumin (OVA) precipitated in alum on days 0 and 5, nebulized weekly with 1% OVA, 1 h, twice daily, for up to 6 weeks, and assessed lung inflammation, mucus hypersecretion, and IgE/IgG1. RESULTS: Kinetic studies revealed that initial aerosol exposure induced high numbers of eosinophils, lymphocytes, and macrophages within lung infiltrates and increased mucus production in wild-type mice. After 3-4 weeks of antigen exposure, eosinophils diminished while lymphocytes, plasma cells, and macrophages and mucus hypersecretion increased. However, by 6 weeks, lung inflammation and mucus hypersecretion were dramatically reduced. In contrast, repeated aerosol challenges maintained OVA-specific IgG1 and IgE production. Repeated aerosol antigen challenges in microMT mice resulted in reduced lung inflammation and mucus hypersecretion and the development of smooth muscle hypertrophy of the pulmonary microvasculature. CONCLUSIONS: B cells and antibody do not appear to play a role in antigen-dependent suppression of allergic responses in mice.

Aerosols↗
PubMed2003

Granulocyte-macrophage colony-stimulating factor-based melanoma cell vaccines immunize syngeneic and allogeneic recipients via host dendritic cells.

Subcutaneous injection of GM-CSF-expressing cancer cells into experimental animals results in protective cancer immunity. To delineate the mode of action of such vaccines, we used trinitrophenyl, the antigenic moiety of the contact allergen trinitrochlorobenzene, as surrogate Ag. Trinitrophenyl-derivatized bone marrow-derived dendritic cells were found to elicit a contact hypersensitivity response in syngeneic, but not in allogeneic recipients, compatible with their expected mode of direct Ag presentation. When expressing GM-CSF, haptenized M3 melanoma cells were also able to induce a contact hypersensitivity response but, in contrast to bone marrow-derived dendritic cells, not only in syngeneic but also in allogeneic recipients. This argues for a critical role of host APC. To identify their nature, we introduced the beta-galactosidase (betagal) gene into M3-GM cells. Their administration activated betagal-specific, L(d)-restricted CTL in syngeneic BALB/c mice. Evaluation of lymph nodes draining M3-GM-betagal injection sites revealed the presence of cells presenting the respective L(d)-binding betagal peptide epitope. Based on their capacity to activate betagal-specific CTL, they were identified as being CD11c(+) dendritic cells. These experiments provide a rational basis for the use of GM-CSF-based melanoma cell vaccines in an allogeneic setting.

Administration, Cutaneous↗
PubMed2003

Definition of TCR epitopes for CTL-mediated attack of cutaneous T cell lymphoma.

Therapeutic vaccination against cutaneous T cell lymphoma (CTCL) requires the characterization of cancer cell-specific CTL epitopes. Despite reported evidence for tumor-reactive cytotoxicity in CTCL patients, the nature of the recognized determinants remains elusive. The clonotypic TCR of CTCL cells is a promising candidate tumor-specific Ag. In this study, we report that the clonotypic and framework regions of the TCRs expressed in the malignant T cell clones of six CTCL patients contain multiple peptides with anchor residues fitting the patients' MHC class I molecules. We demonstrate that TCR peptide-specific T cells from the blood of healthy donors and patients can be induced to become cytotoxic effectors after repeated stimulation with 6 of 11 selected peptides with experimentally proven affinity for HLA-A*0201. Importantly, 4 of these 6 CTL lines reproducibly recognize and lyse autologous primary CTCL cells in MHC class I/CD8-dependent fashion. These tumoricidal CTL lines are directed against epitopes from V, hypervariable, and C regions of TCRalpha. We therefore conclude that recombined as well as V framework regions of the tumor cell TCRs contain predictable epitopes for CTL-mediated attack of CTCL cells. Our data further suggest that such peptides represent valuable tools for future anti-CTCL vaccination approaches.

Amino Acid Sequence↗
PubMed2003

IL-23 production by cosecretion of endogenous p19 and transgenic p40 in keratin 14/p40 transgenic mice: evidence for enhanced cutaneous immunity.

p40, the common subunit of the proinflammatory cytokines IL-12 and IL-23, is produced by resident skin cells. Whereas the in vivo effects of IL-12 are well established, little is known about the role of IL-23 in cutaneous immune responses. In this study we show that p40 transgenic (TG) mice constitutively produce IL-23 (p19/p40), but not IL-12 (p35/p40), in basal keratinocytes by cosecretion of TG p40 with endogenous p19. Repeated injections of rIL-23 in littermate (LM) mice result in an inflammatory skin disease similar to that of p40 TG mice, confirming the proinflammatory activity of IL-23. Furthermore, IL-23 secretion by p40 TG keratinocytes induces elevated numbers of Langerhans cells (LC) with a marked up-regulation of costimulatory molecules, indicating advanced maturation of keratin 14 (K14)/p40 LC when compared with LM LC. At the functional level, freshly isolated K14/p40 LC greatly exceeded LC from LM animals in their capacity to stimulate allogeneic T cell proliferation. To assess whether IL-23 regulates cutaneous immune responses in vivo, we used an allogeneic skin transplantation model. Full thickness skin grafts from K14/p40 donors (H-2(q)) transplanted across a MHC class I and class II barrier onto BALB/c (H-2(d)) recipients were rejected in a significantly accelerated fashion (mean survival time: 8.8 days) when compared with skin grafts from non-TG LM (H-2(q)) (mean survival time: 10.7 days, p < 0.01). Based on these results we propose that IL-23-induced changes of LC may be an important mechanism in directing the outcome of cutaneous immune responses.

Animals↗
PubMed2003

Pemphigoid gestationis: treatment with immunoapheresis.

BACKGROUND: Pemphigoid (herpes) gestationis is a rare blistering disease of pregnancy. Topical and systemic corticosteroids and antihistamines are usually sufficient for treatment. CASE REPORT: A patient suffering from severe, therapy-resistant pemphigoid gestationis was successfully treated with the additional use of six sessions of immunoapheresis. Systemic corticosteroids could be tapered and serum autoantibody levels to bullous pemphigoid antigen 2 (BPAG2 = BP180) significantly dropped during this treatment. CONCLUSION: Immunoapheresis represents a helpful therapeutic option with few side effects for severe cases of pemphigoid gestationis, unresponsive to conventional treatment.

Adrenal Cortex Hormones↗
PubMed2003

Immunopathologic features of allergic contact dermatitis in humans: participation of plasmacytoid dendritic cells in the pathogenesis of the disease?

Contrary to our abundant knowledge about the sensitization phase of human contact hypersensitivity, little is known about the cell types orchestrating the effector phase. In order to address this issue, we phenotypically analyzed biopsies from 72 h epicutaneous patch test reactions (n=10) and normal human skin (n=5) for the presence of various leukocyte differentiation antigens. The inflammatory infiltrate was dominated by CD3+/CD4+ T cells with approximately 30% of the cells coexpressing CD25 and CTLA-4, a phenotype consistent with either activated effector or regulatory T cells. In our search for professional antigen-presenting cells, we were surprised to find not only sizeable numbers of CD1a+ dendritic cells and CD1c+ dendritic cells, but also of CD123+, CD45RA+, BDCA-2+, CLA+, and CD62L+ plasmacytoid dendritic cells. Although virtually absent in normal human skin, these cells were detectable already 6 h after hapten challenge and were often found in close proximity to CD56+ natural killer cells, indicative of a functional interaction between these cell types. The detailed knowledge of the cellular composition of the inflammatory infiltrate in allergic contact dermatitis and its kinetics should form the basis for the investigation of the immunologic and molecular events operative in the perpetuation and resolution of the eczematous response.

Antigens, CD↗
PubMed2002

Long-lived Th2 memory in experimental allergic asthma.

Although life-long immunity against pathogens is beneficial, immunological memory responses directed against allergens are potentially harmful. Because there is a paucity of information about Th2 memory cells in allergic disease, we established a model of allergic asthma in BALB/c mice to explore the generation and maintenance of Th2 memory. We induced disease without the use of adjuvants, thus avoiding Ag depots, and found that unlike allergic asthma in mice immunized with adjuvant, immunizing with soluble and aerosol OVA resulted in pathological lung lesions resembling human disease. To test memory responses we allowed mice with acute disease to recover and then re-exposed them to aerosol OVA a second time. Over 400 days later these mice developed OVA-dependent eosinophilic lung inflammation, airway hyperresponsiveness, mucus hypersecretion, and IgE. Over 1 year after recuperating from acute disease, mice had persistent lymphocytic lung infiltrates, Ag-specific production of IL-4 and IL-5 from spleen and lung cells in vitro, and elevated IgG1. Moreover, when recuperated mice were briefly aerosol challenged, we detected early expression of Th2 cytokine RNA in lungs. Taken together, these data demonstrate the presence of long-lived Th2 memory cells in spleen and lungs involved in the generation of allergic asthma upon Ag re-exposure.

Acute Disease↗
PubMed2002

Induction of specific immune responses by polycation-based vaccines.

The s.c injection of tumor Ag-derived, MHC class I-binding peptides together with cationic poly-amino acids (e.g., poly-L-arginine; pR) has been shown to protect animals against a challenge with tumor cells expressing the respective peptide(s). Given our only restricted knowledge about immunogenic tumor-associated peptides, we sought to determine whether this pR-based vaccination protocol would also induce protective cancer immunity if large proteins were used instead of peptide epitopes. We found that the intracutaneous administration of the model Ag beta-galactosidase (beta-gal) together with pR (referred to as pR-based protein vaccine; pR-PV) was significantly more potent in protecting mice against the growth of beta-gal-expressing RENCA cells than the protein alone. Coadministration of pR enhanced both the beta-gal-induced specific humoral and CD8 response. The protective effect required CD8(+), but neither CD4(+) T lymphocytes nor beta-gal-specific Abs. beta-Gal priming of protective CD8(+) T lymphocytes was found to be CD4(+) T cell-independent, to take place within the draining lymph nodes, and to be accomplished by day 5 after vaccination. Ablation of the injection sites as early as 1.5 h after pR-PV administration still led to protection in a large proportion of the animals, indicating that certain protein Ags administered intradermally in the context of polycations are quickly transported to the draining nodes, where they induce molecular and cellular events resulting in the helper-independent priming and expansion of Tc1 cells. However, optimal protection required the prolonged presence of the injection site, suggesting that pR-PV injection facilitates the formation of a cutaneous depot of Ag-charged cells capable of migration and T cell activation.

Adjuvants, Immunologic↗
PubMed2002

Recurrent aerosol antigen exposure induces distinct patterns of experimental allergic asthma in mice.

Patients with allergic asthma present clinically with chronic or intermittent disease caused by either persistent or periodic allergen exposure. We sought to generate clinically relevant disease in mice, which would reflect the relapsing, remitting, and constant nature of this syndrome. We generated and compared acute onset, remission, relapse, and overt phases of the disease and found that acute disease was characterized by airway hyperreactivity, eosinophilic lung inflammation, excessive mucus production, and antigen-specific antibody and was rapidly followed by a remission. Mice rechallenged with aerosol antigen during the remission or treated with repeated aerosol challenges developed relapse and overt disease, respectively. Recurrent antigen exposure induced a progressive increase in bronchoalveolar lavage fluid immunoglobulin, mucus production, and a change in inflammatory infiltrates indicating a transition from acute to chronic inflammation. These data demonstrate distinct phases of disease representing a clinical spectrum of experimental allergic asthma and may have important implications for new treatment strategies.

Allergens↗
PubMed2002

Systemic administration of antigen-pulsed dendritic cells induces experimental allergic asthma in mice upon aerosol antigen rechallenge.

Antigen-pulsed dendritic cells (DCs) have been used extensively as cellular vaccines to induce a myriad of protective immune responses. Adoptive transfer of antigen-pulsed DCs is especially effective at generating Th1 and CD8 immune responses. However, recently this strategy has been shown to induce Th2 cells when DCs are administered locally into the respiratory tract. We sought to address whether systemic rather than local antigen-pulsed DC administration could induce Th2 experimental allergic asthma. We found that OVA-pulsed splenic DCs injected intraperitoneally induced polarized Th2 allergic lung disease upon secondary OVA aerosol challenge. Disease was characterized by eosinophilic lung inflammation, excess mucus production, airway hyperresponsiveness, and OVA-specific IgG1 and IgE. In addition, unusual pathology characterized by macrophage alveolitis and multinucleated giant cells was observed. These data show that systemic administration of antigen-pulsed DCs and subsequent aeroantigen challenge induces Th2 immunity. These findings have important implications for the development of DC-based vaccines.

Adoptive Transfer↗
PubMed2002

Overexpression of IL-4 alters the homeostasis in the skin.

IL-4 has been implicated to play an important role in the pathogenesis of many inflammatory diseases including skin diseases such as atopic dermatitis. Because it is not clear which pathologic features of atopic dermatitis are dependent on IL-4, we assessed the consequences of IL-4 overexpression in the skin, using transgenic mice overexpressing IL-4 ubiquitously. Although transgenic mice display no clinical signs of skin inflammation, IL-4 induced a wide spectrum of pathologies including an increased number of mast cells and Langerhans cells in dermis and epidermis, respectively, focal deposition of collagen and a considerably reduced adipocyte layer in the dermis as well as an increased mitotic activity of keratinocytes, reflected in acanthosis and hyperkeratosis. The increase in Langerhans cell number may be explained in part by the substantially reduced Langerhans cell emigration from the epidermis in transgenic mice. The molecular mechanism behind this phenomenon remains to be clarified. Under in vitro culture conditions, Langerhans cells from transgenic mice undergo a maturation process similar to that of Langerhans cells from control mice, and their immunostimulatory capacity is also comparable. In contrast, transgenic Langerhans cells are superior to control Langerhans cells in their antigen-processing capacity. We conclude that the overexpression of IL-4 in the skin is, by itself, not sufficient for the induction of a full-blown atopic dermatitis phenotype, but several changes seen in the skin of transgenic mice mirror the cardinal pathologic manifestations of this disease.

Adipocytes↗