Biomedical subjects

Jonathan R Lamb

Publications and source records attributed to Jonathan R Lamb.

At least 19 recordsLinked to original sources

PubMed2006

Characterisation of the binding of amyloid imaging tracers to rodent Abeta fibrils and rodent-human Abeta co-polymers.

Despite the application of amyloid imaging agents such as PIB, SB13, and FDDNP in Alzheimer's disease (AD) patients, the successful use of these agents in transgenic mice models of AD has not been reported to date. As a first step in understanding the behaviour of these ligands in transgenic models of AD, we have investigated in a series of in vitro ligand binding assays the interaction of selected agents, including PIB, FDDNP, SB13, and BSB, with amyloid fibrils produced from rodent Abeta(1-40) (roAbeta) peptide. The data indicate that the ligand binding affinities together with the pattern and number of binding sites on the roAbeta fibrils are broadly conserved with that reported previously for human Abeta(1-40) (huAbeta) fibrils. However, characterisation of huAbeta fibrils formed in the presence of increasing amounts of roAbeta (1, 5, 10% w/w) demonstrated a dose-dependent reduction in the number of high affinity [(3)H]Me-BTA-1 binding sites such that at the highest amount of roAbeta the specific signal was reduced by approximately 95%. These studies suggest that (i) the presence of small amounts of roAbeta in huAbeta fibrils has the potential to cause subtle ultrastructural alterations in the polymers and (ii) the weak binding signal observed in vivo in the transgenic mouse models of AD may in part be due to the decreased number of high affinity binding sites on the Abeta fibrils.

Amyloid beta-Peptides↗

PubMed2005

Suppression of allergic airway inflammation by helminth-induced regulatory T cells.

Allergic diseases mediated by T helper type (Th) 2 cell immune responses are rising dramatically in most developed countries. Exaggerated Th2 cell reactivity could result, for example, from diminished exposure to Th1 cell-inducing microbial infections. Epidemiological studies, however, indicate that Th2 cell-stimulating helminth parasites may also counteract allergies, possibly by generating regulatory T cells which suppress both Th1 and Th2 arms of immunity. We therefore tested the ability of the Th2 cell-inducing gastrointestinal nematode Heligmosomoides polygyrus to influence experimentally induced airway allergy to ovalbumin and the house dust mite allergen Der p 1. Inflammatory cell infiltrates in the lung were suppressed in infected mice compared with uninfected controls. Suppression was reversed in mice treated with antibodies to CD25. Most notably, suppression was transferable with mesenteric lymph node cells (MLNC) from infected animals to uninfected sensitized mice, demonstrating that the effector phase was targeted. MLNC from infected animals contained elevated numbers of CD4(+)CD25(+)Foxp3(+) T cells, higher TGF-beta expression, and produced strong interleukin (IL)-10 responses to parasite antigen. However, MLNC from IL-10-deficient animals transferred suppression to sensitized hosts, indicating that IL-10 is not the primary modulator of the allergic response. Suppression was associated with CD4(+) T cells from MLNC, with the CD4(+)CD25(+) marker defining the most active population. These data support the contention that helminth infections elicit a regulatory T cell population able to down-regulate allergen induced lung pathology in vivo.

Animals↗

PubMed2005

Notch1 co-localizes with CD4 on activated T cells and Notch signaling is required for IL-10 production.

The effector function of activated CD4(+) T cells and secretion of cytokines are important in the establishment of productive immune responses and tolerance. We identified expression by CD4(+) T cells of Notch receptors and ligands and enhanced Notch signaling upon activation. Notch1 expression was up regulated and co-localized with CD4 upon T cell stimulation. Disruption of Notch signaling did not affect proliferation, but attenuated cytokine secretion following CD3 ligation in the absence of anti-CD28 antibody. Notch signaling was absolutely necessary for transcription of IL-10 by stimulated CD4(+) T cells. CD4(+) T cells transfected with constitutively active Notch1 failed to proliferate, but exhibited enhanced cytokine secretion upon stimulation. Our data indicates that Notch receptor signaling can influence both proliferative and cytokine responses of CD4(+) T cells. In addition, the finding that Notch signaling is required for production of IL-10 may allude to a role in immune regulation.

Animals↗

PubMed2005

FITC-induced murine pulmonary inflammation: CC10 up-regulation and concurrent Shh expression.

We describe an immunohistochemical study of the acute and chronic effects of fluorescein isothiocyanate (FITC) on Sonic hedgehog (Shh) expression and Clara cell secretory protein (CC10) up-regulation in murine lung. FITC was dissolved in PBS and instilled non-surgically into adult mouse lungs via the trachea. During the acute phase (120h) of the FITC response, CC10 staining within Clara cells increased markedly but the protein did not leak into the tissue spaces or the airways, and no fibrosis was apparent. An immune response was evident, characterised by infiltrating T and B lymphocytes. There was no concomitant expression of Shh. During the chronic phase (6 months post-instillation), significant tissue degeneration was observed in the airways. There was moderate to severe fibrosis in the lung fields that stained positively for FITC and significant inflammatory cell infiltrate was observed. Shh was expressed, and CC10 showed multiple sites of diffuse staining consistent with release from Clara cells into alveolar air spaces. PBS controls showed no fibrosis after 6 months, but there was positive Shh staining below the airway epithelia and minimal extracellular CC10 staining. The results may throw some light on the role of CC10 in pulmonary inflammation. The relationship of Shh expression and CC10 leakage to lung damage and repair is discussed.

Acute Disease↗

PubMed2005

Notch: control of lymphocyte differentiation in the periphery.

The complexity of the Notch signalling pathway has impeded progress in understanding its precise role in differentiation processes of the mature peripheral immune system. Nevertheless, both B and T lymphocyte responses are undoubtedly influenced by Notch ligation, and defining the mechanisms by which this is achieved remains a challenge. How the innate-adaptive interface and interactions between lymphocytes can be affected, together with the potential of this pathway for therapeutic intervention remain important and stimulating issues.

Animals↗

PubMed2004

Acceleration of apoptosis in CD4+CD8+ thymocytes by rapamycin accompanied by increased CD4+CD25+ T cells in the periphery.

BACKGROUND: Rapamycin (Rapa) is an immunosuppressant that is used in patients and animal models to control allograft rejection. Its mechanisms of action are not fully understood. In this article, the authors have investigated the effects of therapeutic doses of Rapa on both thymic and peripheral T-cell populations in the adult rat. METHODS: The therapeutic dosage of Rapa was optimized using cardiac transplantation between LEW and DA rats. Thymic morphology was assessed by hematoxylin-eosin staining. Flow cytometric analysis was performed to analyze T-cell phenotype and apoptosis. T-cell receptor (TCR)-mediated T-cell responsiveness was evaluated by 3[H]-thymidine deoxyribose incorporation. RESULTS: Rapa induced atrophy in the thymus but not in peripheral lymphoid organs. Moreover, fibrosis occurred in thymus that was long-lasting after Rapa withdrawal. In animals treated with Rapa, there was a significant reduction in CD4+CD8+ thymocytes caused by accelerated apoptosis, whereas CD4-CD8-, CD4+CD8-, and CD8+CD4- populations remained unaffected. In contrast, the cellularity of the periphery lymphoid organs was not altered. Within the CD4+ thymocyte population, CD4+CD25+ thymocytes were resistant to Rapa-accelerated apoptosis, and in the periphery, the ratio of CD4+CD25+ to CD4+CD25- T cells was increased. Notably, the peripheral CD4+CD25+ T cells were hyporesponsive to TCR-mediated activation. CONCLUSIONS: The resistance of the peripheral CD4+CD25+ T cells to Rapa treatment might contribute to its immunosuppressive action. The long-term effects of Rapa on thymus atrophy and thymocyte development requires consideration with respect to its clinical application.

Animals↗

PubMed2004

The Notch and Sonic hedgehog signalling pathways in immunity.

There is an increasing body of knowledge demonstrating that genes involved in cell fate decisions during development also play a role in the continuous cell fate decisions made by the mature immune system in response to foreign antigen. This review concentrates on the role of the Notch and Sonic hedgehog (Shh) signalling pathways in the development and function of CD4+ T lymphocytes.

Animals↗

PubMed2004

Reversal of established CD4+ type 2 T helper-mediated allergic airway inflammation and eosinophilia by therapeutic treatment with DNA vaccines limits progression towards chronic inflammation and remodelling.

Immunostimulatory DNA-based vaccines can prevent the induction of CD4(+) type 2 T helper (Th2) cell-mediated airway inflammation in experimental models, when administered before or at the time of allergen exposure. Here we demonstrate their efficacy in limiting the progression of an established response to chronic pulmonary inflammation and airway remodelling on subsequent allergen challenge. Mice exhibiting Th2-mediated airway inflammation induced following sensitization and challenge with group 1 allergen derived from Dermatophagoides pteronyssinus group species (Der p 1), a major allergen of house dust mite, were treated with pDNA vaccines. Their airways were rechallenged and the extent of inflammation assessed. In plasma DNA (pDNA)-vaccinated mice, infiltration of inflammatory cells, goblet cell hyperplasia and mucus production were reduced and subepithelial fibrosis attenuated. The reduction in eosinophil numbers correlated with a fall in levels of the profibrotic mediator transforming growth factor (TGF)-beta1 in bronchoalveolar lavage (BAL) and lung tissue. In addition to lung epithelial cells and resident alveolar macrophages, infiltrating eosinophils, the principle inflammatory cells recruited following allergen exposure, were a major source of TGF-beta1. Protection, conferred irrespective of the specificity of the pDNA construct, did not correlate with a sustained increase in systemic interferon (IFN)-gamma production but in a reduction in levels of the Th2 pro-inflammatory cytokines. Notably, there was a reduction in levels of interleukin (IL)-5 and IL-13 produced by systemic Der p 1 reactive CD4(+) Th2 cells on in vitro stimulation as well as in IL-4 and IL-5 levels in BAL fluid. These data suggest that suppression of CD4(+) Th2-mediated inflammation and eosinophilia were sufficient to attenuate progression towards airway remodelling. Immunostimulatory DNA may therefore have a therapeutic application in treatment of established allergic asthma in patients.

Allergens↗

PubMed2004

The role of vascular endothelial growth factor in the kidney in health and disease.

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen, angiogenic factor and enhancer of vascular permeability. Expressed in the epithelial cells of the developing glomerulus and tubular epithelium, VEGF plays an important role in the development and maintenance of the early vasculature of the kidney. Here, we review the available literature regarding the expression and function of VEGF both in the developing and healthy adult kidney. Furthermore, we highlight how VEGF expression is altered in the diseased kidney and how this modulated expression may impact on and reflect underlying functional changes occurring during the disease process. As discussed, many controversial issues remain, particularly concerning the role of VEGF in the diseased kidney. That VEGF has been proposed as a potential future therapeutic target for the management of some renal diseases requires first that the precise role of VEGF in the normal kidney and various renal pathologies be further and more clearly defined.

Animals↗

PubMed2003

Suppression of allergen reactive Th2 mediated responses and pulmonary eosinophilia by intranasal administration of an immunodominant peptide is linked to IL-10 production.

The potential to induce systemic tolerance following exposure of the airway mucosa to soluble antigen, may be applied therapeutically for the treatment of allergic disease. Since the use of allergen can trigger IgE mediated inflammation, we investigated whether mucosal delivery of a peptide, containing an immunodominant epitope of the Der p1 allergen of house dust mite, can lead to CD4(+) Th2 cell tolerance and thus protect against airway inflammatory responses to inhalant allergen. The administration of microencapsulated peptide to the nasal mucosa of mice, protected against airway inflammation, with significant reductions in eosinophil infiltration into the airways following allergen challenge. Der p1 specific antibody levels in sera were not modulated. Allergen reactive CD4(+) T cells expressed a tolerized phenotype, with reduction in levels of the cytokines, IL-5, IL-13 and IFN-gamma although IL-10 levels were increased. The mucosal administration of a peptide containing an immunodominant region of an allergen can protect against the induction of systemic and local inflammatory responses to allergen challenge.

Allergens↗

PubMed2003

Expression of the developmental Sonic hedgehog (Shh) signalling pathway is up-regulated in chronic lung fibrosis and the Shh receptor patched 1 is present in circulating T lymphocytes.

During pulmonary development, Sonic hedgehog (Shh) and transforming growth factor beta1 (TGF-beta1) signalling both contribute to branching morphogenesis. In interstitial lung disease, the complex alveolar structure of the lung is disrupted and remodelled, which leads to fibrosis, loss of respiratory surface, morbidity, and mortality. It is well documented that TGF-beta1 is involved in fibrosis. However, little is known about Shh signalling in damaged epithelia. This study examined whether or not components of the Shh signalling pathway, as well as TGF-beta1, are expressed in human fibrotic lung disease (cryptogenic fibrosing alveolitis and bronchiectasis) and in murine experimental models of fibrotic and non-fibrotic chronic pulmonary inflammation. Using immunohistochemistry, it was observed that Shh, like TGF-beta1, is up-regulated in epithelial cells at sites of fibrotic disease but not non-fibrotic inflammation. The Shh receptor patched was detected in infiltrating mononuclear cells and alveolar macrophages, as well as normal resting peripheral blood T lymphocytes. Neither Shh nor patched is expressed by hyperproliferative goblet cells in inflammatory epithelium. This study demonstrates that patched is present in human peripheral CD4 and CD8 lymphocytes at both protein and mRNA levels. Taken together, these results suggest that components of the highly conserved Shh signalling pathway may play a role in the remodelling of damaged pulmonary epithelium and that damaged epithelium and cells of the immune system may communicate via this pathway.

Animals↗

PubMed2003

Notch signalling in the regulation of peripheral T-cell function.

The Notch signalling pathway plays a highly-conserved role in regulating the cellular differentiation and proliferation events that characterise pattern formation in the embryo. As cells in the embryo respond to environmental signals, similarly T-cells in the peripheral immune system must monitor their environment for antigens and respond accordingly by entering one of several potential differentiation pathways. Recent studies have identified a role for the Notch pathway in regulating the responses of T-cells in the periphery. In this review, we discuss these findings in the context of the Notch signalling pathway's role as an orchestrator of cellular differentiation, and propose a central role for Notch as a regulator of immune system function.

Animals↗

PubMed2003

Notch ligation by Delta1 inhibits peripheral immune responses to transplantation antigens by a CD8+ cell-dependent mechanism.

Notch signaling plays a fundamental role in determining the outcome of differentiation processes in many tissues. Notch signaling has been implicated in T versus B cell lineage commitment, thymic differentiation, and bone marrow hematopoietic precursor renewal and differentiation. Notch receptors and their ligands are also expressed on the surface of mature lymphocytes and APCs, but the effects of Notch signaling in the peripheral immune system remain poorly defined. The aim of the studies reported here was to investigate the effects of signaling through the Notch receptor using a ligand of the Delta-like family. We show that Notch ligation in the mature immune system markedly decreases responses to transplantation antigens. Constitutive expression of Delta-like 1 on alloantigen-bearing cells renders them nonimmunogenic and able to induce specific unresponsiveness to a challenge with the same alloantigen, even in the form of a cardiac allograft. These effects could be reversed by depletion of CD8+ cells at the time of transplantation. Ligation of Notch on splenic CD8+ cells results in a dramatic decrease in IFN-gamma with a concomitant enhancement of IL-10 production, suggesting that Notch signaling can alter the differentiation potential of CD8+ cells. These data implicate Notch signaling in regulation of peripheral immunity and suggest a novel approach for manipulating deleterious immune responses.

Animals↗

PubMed2003

Notch signalling in the peripheral immune system.

Peripheral T cell tolerance is critical in the regulation of immune responses to self antigens, and has implications in the control of autoimmunity, allergic responses and transplant rejection. Here we discuss recent and unpublished data demonstrating that ligation of the cell surface receptor Notch on T cells inhibits immune responses and results in the generation of a regulatory T cell population. Using animal models, we show that prior exposure to antigen can inhibit the response to challenge in an antigen-specific fashion. This inhibition is accompanied by the generation of cells with apparent regulatory capacity and we further show that exposure of T cells to Notch and T cell receptor signals together enhances interleukin 10 production, at least in cell culture systems. We discuss how Notch signalling may integrate with other signals to induce tolerance.

Animals↗

PubMed2002

Sonic hedgehog signaling modulates activation of and cytokine production by human peripheral CD4+ T cells.

Sonic hedgehog (Shh) is important in the growth and differentiation of a variety of cell types, including the development of T cells in the thymus. This prompted us to investigate whether Shh signaling is a functional component of the physiological response of human mature CD4(+) T cells following Ag recognition. In this study, we demonstrate that Shh and its receptor Patched (Ptc) are expressed on resting and activated human peripheral CD4(+) T cells. In approximately one-half of the randomly selected, anonymous blood donors tested, exposure of anti-CD3/28 Ab-activated CD4(+) T cells to the biologically active N-terminal Shh peptide increased the transcription of ptc, thereby demonstrating that Shh signaling had occurred. Furthermore, the addition of exogenous Shh amplified the production of IL-2, IFN-gamma, and IL-10 by activated CD4(+) T cells. The synthesis of IL-2 and IFN-gamma, but not IL-10, by CD4(+) T cells was down-regulated by the addition of neutralizing anti-Shh Ab. Cell surface expression of CD25 and CD69 on activated T cells was up-regulated by exogenous Shh, whereas in the presence of the neutralizing anti-Shh Ab expression it was reduced. Collectively, our findings demonstrate that Shh-mediated signaling is a physiological component of T cell responses, which acts to modulate CD4(+) T cell effector function.

Adjuvants, Immunologic↗

PubMed2002

Sonic hedgehog promotes cell cycle progression in activated peripheral CD4(+) T lymphocytes.

Sonic hedgehog (Shh) signaling is important in the growth and differentiation of many cell types and recently has been reported to play a role in T cell development in the thymus. This prompted us to investigate whether or not Shh contributes to the clonal expansion of peripheral CD4(+) T cells. In this study, we demonstrate that Shh and other components of the signaling pathway patched, smoothened, and Gli1 (glioma-associated oncogene) are expressed in peripheral CD4(+) T cells. The addition of the biologically active amino-terminal Shh peptide had no effect on resting CD4(+) T cells, but significantly enhanced proliferation of anti-CD3/28 Ab-activated CD4(+) T cells. This was not due to antiapoptotic effects, but by promoting entry of T cells into the S-G(2) proliferative phase of the cell cycle. Neutralizing anti-Shh Ab reduced T cell proliferation by inhibiting cell transition into the S-G(2) phase, suggesting that endogenously produced Shh plays a physiological role in the clonal expansion of T cells. Furthermore, we have observed a significant up-regulation of Shh and Gli1 (glioma-associated oncogene) mRNA in activated CD4(+) T cells with or without addition of exogenous Shh, which corresponds with maximal CD4(+) T cell proliferation, whereas bcl-2 was only up-regulated in activated cells in the presence of Shh. Our findings suggest that endogenously produced Shh may play a role in sustaining normal CD4(+) T cell proliferation and exogenously added Shh enhances this response.

Animals↗

PubMed2002

Inhibition of TCR-mediated shedding of L-selectin (CD62L) on human and mouse CD4+ T cells by metalloproteinase inhibition: analysis of the regulation of Th1/Th2 function.

The generation of a productive primary immune response is dependent on the ability of naïve T lymphocytes to recirculate through peripheral lymph organs to encounter specific antigen. The process of naïve CD4(+) T cell entry into lymph nodes correlates with cell surface expression of L-selectin (CD62L), which mediates early tethering and rolling events to endothelium prior to entry. Here, we demonstrate that surface expression of CD62L enhances CD4(+) T cell activation in vitro. The synthetic hydroxamate metalloproteinase inhibitor (BB-3103), specifically inhibits activation-induced shedding of CD62L from CD4(+) T cells by TCR cross-linking and lowers proliferation in part by reducing rapid tyrosine phosphorylation of zeta-associated protein 70 kDa (ZAP-70) and by increasing cytosolic free Ca(2+) concentration mobilization. BB-3103 also inhibited the proliferative response of both murine CD4(+) Th1 and Th2 subsets in vitro but the inhibitory effects were sustained only in Th2-type cells. Similarly, BB-3103 mediated prolonged inhibition of allergen-dependent peripheral T cell proliferation in atopic dermatitis patients but not in healthy controls. Analysis of CD62L expression on murine CD4(+) T cell subsets revealed that surface expression was maintained on Th1 cells but not Th2 cells. The differential effects of BB-3103 on primed effector CD4(+) T cells may provide new insights into generating therapeutic agents capable of redressing the Th2/Th1 imbalance in allergic diseases.

Animals↗

PubMed2002

Different profile of CD8+ effector T cells induced in Der p 1-allergic and naïve mice by DNA vaccination.

DNA vaccination holds great promise in both prophylactic and therapeutic vaccines. Recent evidence suggests that DNA vaccines could be powerful therapies countering Th2-mediated disorders such as allergies. Here, we studied the allergen-specific CD4+ and CD8+ T cell populations induced following immunization of allergic and non-allergic mice with DNA vaccine vectors encoding discrete epitopes of the house dust mite (HDM) Dermatophagoides pteronyssinus group I (Der p 1) allergen. Specifically, mice were sensitized to Der p 1 and exhibited a strong Th2/allergic response. Sensitized and non-allergic mice were then compared for their responses to DNA immunization. Using Elispot analysis, we demonstrate that allergic/vaccinated mice generate a mixed Th1/Th2 response against the allergen with high numbers of allergen-specific CD4+ T cells secreting IFN-gamma or IL-4, whereas in non-allergic/vaccinated mice a polarized Th1 response was dominant. Allergen-specific CD8+ T cells secreting IFN-gamma were induced at equal frequencies in both allergic and non-allergic mice. However, the CD8+ T cells from allergic mice were markedly deficient in their cytotoxic potential when compared to their counterparts in non-allergic mice. These results indicate that during an ongoing Th2 response, DNA vaccination leads to the generation of a distinct population of non-cytotoxic/regulatory CD8+ T cells.

Allergens↗