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Angus W Thomson

Publications and source records attributed to Angus W Thomson.

At least 55 records · Page 3Linked to original sources
PubMed2003

Dendritic cell subsets in blood and lymphoid tissue of rhesus monkeys and their mobilization with Flt3 ligand.

We provide phenotypic and functional evidence of premonocytoid dendritic cells (DCs) and preplasmacytoid DCs in blood and of corresponding DC subsets in secondary lymphoid tissue of rhesus monkeys. Subsets were identified and sorted by 4-color flow cytometry using antihuman monoclonal antibodies cross-reactive with rhesus monkey. To mobilize pre-DC subsets, fms-like tyrosine 3 kinase ligand (Flt3L; 100 microg/kg subcutaneously) was administered for 10 days. Presumptive pre-DC subsets were identified within the lineage- (Lin-) major histocompatibility complex (MHC) class II+ fraction of blood mononuclear cells. Premonocytoid DCs were CD11c+CD123- (interleukin-3Ralpha- [IL-3Ralpha-]). Preplasmacytoid DCs were characterized as CD11c-CD123++ Flt3L increased the CD11c+ pre-DC (7-fold) and CD123++ pre-DC subsets (3-fold) in blood. The freshly isolated CD11c+ pre-DC subset induced modest proliferation of naive allogeneic T cells. After overnight culture with granulocyte macro-phage-colony-stimulating factor (GMCSF) and CD40L, both subsets up-regulated surface costimulatory molecules, and CD11c+ pre-DCs became potent allostimulators. Freshly isolated CD123++ pre-DCs showed typical plasmacytoid morphology and, when cultured with IL-3 and CD40L for 72 hours, developed mature DC morphology. Following stimulation with CD40L, CD11c+ pre-DCs secreted increased levels of IL-12p40. Importantly, herpes simplex virus-stimulated CD123++ pre-DCs, but not CD11c+ pre-DCs, secreted interferon-alpha (IFN-alpha). Corresponding DC subsets were identified by flow analysis and immunohistochemistry in lymph nodes wherein both populations were increased 2- to 3-fold by Flt3L administration. CD123+ pre-DCs produced IFN-alpha in response to in vivo viral infection. Thus, rhesus monkeys exhibit 2 distinct DC precursor populations that closely resemble those of humans. Both are mobilized into blood and lymphoid tissue by Flt3L, offering potential for their further characterization and possible therapeutic application.

Animals↗
PubMed2003

Pharmacologic, biologic, and genetic engineering approaches to potentiation of donor-derived dendritic cell tolerogenicity.

There are various approaches to the enhancement of dendritic cell (DC) tolerogenicity for the promotion of cell or organ allograft survival. Both pharmacologic and biologic agents, including several commonly used immunosuppressive drugs, and specific anti-inflammatory cytokines inhibit DC maturation, whereas co-stimulation-blocking agents can also promote the induction of antigen-specific T-cell unresponsiveness by DC. Delivery of genes encoding molecules that subvert T-cell responses by various mechanisms, and targeting of DC migration by selective manipulation of chemokine and chemokine receptor expression, represent additional promising strategies. In this short review, the authors consider those approaches that have been used to promote the tolerogenicity of donor-derived DC in experimental models. Whereas most work to date has focused on myeloid DC, manipulation of other DC subsets may also offer potential for improving the outcome of transplantation and enhancing tolerance induction.

Animals↗
PubMed2003

Rapamycin inhibits IL-4--induced dendritic cell maturation in vitro and dendritic cell mobilization and function in vivo.

Rapamycin (RAPA) is a potent immunosuppressive macrolide hitherto believed to mediate its action primarily via suppression of lymphocyte responses to interleukin 2 (IL-2) and other growth factors. We show here that this view is incomplete and provide evidence that RAPA suppresses the functional activation of dendritic cells (DCs) both in vitro and in vivo. In vitro, RAPA inhibits IL-4-dependent maturation and T-cell stimulatory activity of murine bone marrow-derived DCs. These effects are associated with posttranscriptional down-regulation of both subunits of the IL-4 receptor complex (CD124, CD132) and are mediated via binding of RAPA to its intracellular receptor FK506-binding protein 12 (FKBP12). In vivo, RAPA impairs steady-state DC generation and fms-like tyrosine 3 kinase ligand (Flt3L)-induced DC mobilization. In addition, in vivo administration of RAPA impairs DC costimulatory molecule up-regulation, production of proinflammatory cytokines, and T-cell allostimulatory capacity. These novel findings have implications for RAPA-based therapy of chronic DC-triggered autoimmune diseases, transplant rejection, and hematologic malignancies with activating Flt3 mutations.

Animals↗
PubMed2003

Type-1 polarized nature of mouse liver CD8alpha- and CD8alpha+ dendritic cells: tissue-dependent differences offset CD8alpha-related dendritic cell heterogeneity.

Interleukin-12 p70 (IL-12p70) is a major dendritic cell (DC)-produced cytokine known to support type-1 T helper (Th1) cells and inflammatory-type immunity. While the ability of DC to produce bioactive IL-12p70 depends on both the DC subtype and the microenvironmental conditions of DC development, the relative contribution of each of these factors remains unclear. Here, we report that in contrast to spleen CD8alpha+ and CD8alpha- DC that show strong differences in their respective IL-12p70-producing capacities, CD8alpha+ and CD8alpha- DC isolated from the liver, a non-lymphoid organ, both efficiently produce IL-12p70 in amounts comparable to spleen CD8alpha+ DC. The IL-12p70-producing capacity CD8alpha+ and CD8alpha- DC from either location is greatly increased following their overnight culture in the presence of granulocyte-macrophage colony-stimulating factor. The elevated production of IL-12p70 by short-term cultured DC correlates with their enhanced expression of CD40 and other costimulatory molecules, and elevated T cell-stimulatory capacity. These data indicate that low IL-12-producing capacity is not an intrinsic property of the CDalpha8- DC subtype, and support the hypothesis that factors such as the site of DC development and maturation stage play a dominant role in defining DC function.

Animals↗
PubMed2003

Alloantigen presentation by ethylcarbodiimide-treated dendritic cells induces T cell hyporesponsiveness, and prolongs organ graft survival.

Ethylcarbodiimide (ECDI) couples soluble antigens (Ag) to lymphoid cells bestowing tolerizing potential. We examined whether ECDI-treated allogeneic dendritic cells (DC) could promote Ag-specific T cell unresponsiveness and prolong graft survival. Exposure of murine myeloid DC to ECDI did not affect surface immunophenotype but reduced their ability to cluster with T cells, enhanced their apoptotic death, and markedly reduced their allostimulatory activity. Anti-donor proliferative and cytotoxic T cell responses of mice primed with ECDI-treated DC were markedly inhibited. Secretion of both Th1 (IFNgamma) and Th2 cytokines (IL-5, IL-10) was suppressed. Cardiac allograft survival in mice preconditioned with a single injection of ECDI-DC was prolonged significantly. These results indicate that ECDI-treated DC promote T cell unresponsiveness to donor alloAgs and prolong transplant survival. The effects are not associated with sparing of Th2 responses, but may reflect inhibitory effects of apoptotic donor DC on host immune reactivity.

Animals↗
PubMed2003

Dendritic cell subset ratio in peripheral blood correlates with successful withdrawal of immunosuppression in liver transplant patients.

Human dendritic cell (DC) subsets appear to play distinct roles in the induction and regulation of immune responses. While monocytoid DC (DC1) induce T-helper (Th) 1-type responses, plasmacytoid DC (DC2) have been reported to selectively induce Th2 responses. In blood, their precursors (p) can be identified as HLA-DR+ lineage- cells that are further characterized as CD11c+ CD123-/lo (IL-3Ralpha-/lo) (pDC1) or as CD11c- CD123hi (pDC2) by rare event, flow cytometric analysis. We compared the incidences of pDC1 and pDC2 in peripheral blood mononuclear cell populations isolated from normal healthy controls and from 3 groups of clinically stable liver transplant patients. Group A had been successfully withdrawn from immunosuppression, whereas group B were undergoing prospective drug weaning and on minimal anti-rejection therapy. In group C, drug withdrawal had either failed or never been attempted and patients were on maintenance immunosuppression. Assessment of DC subsets and the pDC2 : pDC1 ratio showed good intra-and interassay reproducibility. Compared with patients in group C, those in groups A and B demonstrated a significantly higher relative incidence of pDC2 and a lower incidence of pDC1 - similar to those values observed in normal healthy controls. Moreover, the pDC2 : pDC1 ratio was significantly higher in patients undergoing (successful) weaning and in those off immunosuppression compared with patients on maintenance immunosuppression.

Adolescent↗
PubMed2003

Dendritic cells: regulators of alloimmunity and opportunities for tolerance induction.

Dendritic cells (DCs) are uniquely well-equipped antigen-presenting cells (APCs) regarded classically as sentinels of the immune response, which induce and regulate T-cell reactivity. They play critical roles in central tolerance and in the maintenance of peripheral tolerance in the normal steady state. Following cell or organ transplantation, DCs present antigen to T cells via the direct or indirect pathways of allorecognition. These functions of DCs set in train the rejection response, but they also serve as potential targets for suppression of alloimmune reactivity and promotion of tolerance induction. Much evidence from various model systems now indicates that DCs can induce specific T-cell tolerance. Although underlying mechanisms have not been fully elucidated, the capacity to induce T-regulatory cells may be an important property of tolerogenic or regulatory DCs. Efforts to generate "designer" DCs with tolerogenic properties in the laboratory using specific cytokines, immunologic or pharmacologic reagents, or genetic engineering approaches have already met with some success. Alternatively, targeting of DCs in vivo (e.g. by infusion of apoptotic allogeneic cells) to take advantage of their inherent tolerogenicity has also demonstrated exciting potential. The remarkable heterogeneity and plasticity of these important APCs present additional challenges to optimizing DC-based therapies that may lead to improved tolerance-enhancing strategies in the clinic.

Animals↗
PubMed2002

Differential modulation of CD4 and CD8 T-cell proliferation by induction of nitric oxide synthesis in antigen presenting cells.

BACKGROUND: On antigenic stimulation, CD4 T cells generally proliferate more readily than CD8 T cells. The purpose of the present experiments was to determine whether nitric oxide (NO) might differentially modulate CD4 vs. CD8 T-cell proliferation. METHODS: Various concentrations of C57BL/6 iNOS +/+ and -/- bone marrow (BM)-derived antigen presenting cells (APC) (obtained by culture in granulocyte-macrophage colony-stimulating factor [GM-CSF] and interleukin [IL]-4) were cultured with purified BALB/c CD4 or CD8 T cells. RESULTS: Proliferation of CD4 T cells was similar in the presence of both NO synthase (iNOS) +/+ and -/- APC, whereas CD8 T cell proliferation was inhibited at the higher concentrations of iNOS +/+ dendritic cells (DC), coincident with increased levels of NO in the culture supernatant. Analysis of cytokine levels revealed that more interferon (IFN)-gamma, a potent inducer of NO synthesis in many cell types, was present in CD8 T cell than in CD4 T-cell-APC cultures. Addition of IFN-gamma to CD4 T-cell-APC cultures resulted in induction of NO synthesis and inhibition of proliferation at higher levels of NO than that required to inhibit CD8 T cell proliferation. However, CD4 T-cell proliferation was moderately inhibited in the presence of lipopolysaccharide (LPS)-stimulated CD11c DC, coincident with production of IFN-gamma and induction of NO synthesis. CONCLUSIONS: These findings indicate that CD8 T-cell proliferation can be inhibited by lesser amounts of APC-derived NO than is necessary to inhibit CD4 T cell proliferation. NO synthesis was not initiated in CD4 T cell-DC cultures unless costimulatory molecules were up-regulated and IFN-gamma was produced.

Animals↗
PubMed2002

Marked prolongation of cardiac allograft survival by dendritic cells genetically engineered with NF-kappa B oligodeoxyribonucleotide decoys and adenoviral vectors encoding CTLA4-Ig.

Bone marrow-derived dendritic cells (DCs) can be genetically engineered using adenoviral (Ad) vectors to express immunosuppressive molecules that promote T cell unresponsiveness. The success of these DCs for therapy of allograft rejection has been limited in part by the potential of the adenovirus to promote DC maturation and the inherent ability of the DC to undergo maturation following in vivo administration. DC maturation occurs via NF-kappaB-dependent mechanisms, which can be blocked by double-stranded "decoy" oligodeoxyribonucleotides (ODNs) containing binding sites for NF-kappaB. Herein, we describe the combined use of NF-kappaB ODNs and rAd vectors encoding CTLA4-Ig (Ad CTLA4-Ig) to generate stably immature murine myeloid DCs that secrete the potent costimulation blocking agent. These Ad CTLA4-Ig-transduced ODN DCs exhibit markedly impaired allostimulatory ability and promote apoptosis of activated T cells. Furthermore, administration of Ad CTLA4-Ig ODN-treated donor DCs (C57BL10; B10(H-2b)) before transplant significantly prolongs MHC-mismatched (C3HHeJ; C3H(H-2k)) vascularized heart allograft survival, with long-term (>100 days) donor-specific graft survival in 40% of recipients. The mechanism(s) responsible for DC tolerogenicity, which may involve activation-induced apoptosis of alloreactive T cells, do not lead to skewing of intragraft Th cytokine responses. Use of NF-kappaB antisense decoys in conjunction with rAd encoding a potent costimulation blocking agent offers promise for therapy of allograft rejection or autoimmune disease with minimization of systemic immunosuppression.

Abatacept↗
PubMed2002

Internalization of circulating apoptotic cells by splenic marginal zone dendritic cells: dependence on complement receptors and effect on cytokine production.

Under steady-state conditions, internalization of self-antigens embodied in apoptotic cells by dendritic cells (DCs) resident in peripheral tissue followed by DC migration and presentation of self-peptides to T cells in secondary lymphoid organs are key steps for induction and maintenance of peripheral T-cell tolerance. We show here that, besides this traffic of apoptotic cells mediated by peripheral tissue-resident DCs, splenic marginal zone DCs rapidly ingest circulating apoptotic leukocytes, process apoptotic cell-derived peptides into major histocompatibility complex class II (MHC-II) molecules, and acquire CD8alpha during their mobilization to T-cell areas of splenic follicles. Because apoptotic cells activate complement and some complement factors are opsonins for phagocytosis and play roles in the maintenance of peripheral tolerance, we investigated the role of complement receptors (CRs) in relation to phagocytosis of apoptotic cells by DCs. Apoptotic cell uptake by marginal zone DCs was mediated in part via CR3 (CD11b/CD18) and, to a lesser extent, CR4 (CD11c/CD18) and was reduced significantly in vivo in hypocomplementemic animals. Following phagocytosis of apoptotic cells, DCs exhibited decreased levels of mRNA and secretion of the proinflammatory cytokines interleukin 1alpha (IL-1alpha), IL-1beta, IL-6, IL-12p70, and tumor necrosis factor alpha (TNF-alpha), without effect on the anti-inflammatory mediator transforming growth factor beta1 (TGF-beta1). This selective inhibitory effect was at least partially mediated through C3bi-CD11b/CD18 interaction. Characterization of apoptotic cell/DC interaction and its outcome provides insight into the mechanisms by which apoptotic cells affect DC function without disrupting peripheral tolerance.

Animals↗
PubMed2002

Promotion of skin graft tolerance across MHC barriers by mobilization of dendritic cells in donor hemopoietic cell infusions.

Flt3 ligand (FL) dramatically increases the number of immunostimulatory dendritic cells (DC) and their precursors in bone marrow (BM) and secondary lymphoid tissues. Herein we tested the ability of FL-mobilized donor hemopoietic cells to promote induction of skin graft tolerance across full MHC barriers. C57BL/10 (B10; H2(b), IE(-)) mice were given 10(8) spleen cells (SC) from normal or FL-treated, H-2-mismatched B10.D2 (H2(d), IE(+)) donors i.v. on day 0, 200 mg/kg i.p. cyclophosphamide on day 2, and 10(7) T cell-depleted BM cells from B10.D2 mice on day 3. B10.D2 skin grafting was performed on day 14. Indefinite allograft survival (100 days) was induced in recipients of FL-SC, but not in mice given normal SC. Tolerance was associated with blood macrochimerism and was confirmed by second-set skin grafting with donor skin 100 days after the first graft. In tolerant mice, peripheral donor-reactive T cells expressing TCR Vbeta11 were deleted selectively. Immunocompetence of tolerant FL-SC-treated mice was proven by rapid rejection of third-party skin grafts. To our knowledge this is the first report that mobilization of DC in donor cell infusions can be used to induce skin graft tolerance across MHC barriers, accompanied by specific deletion of donor-reactive T cells.

Adjuvants, Immunologic↗
PubMed2002

Rapamycin inhibits macropinocytosis and mannose receptor-mediated endocytosis by bone marrow-derived dendritic cells.

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that use 2 major pathways for antigen uptake: constitutive macropinocytosis and mannose receptor-mediated endocytosis. Efficient endocytosis is critical for DCs to fulfill their sentinel function in immunity. We investigated the influence of the immunosuppressive macrolide rapamycin on macropinocytosis of fluorescein isothiocyanate (FITC)-albumin and mannose receptor-mediated endocytosis of FITC-dextran by murine bone marrow-derived DCs by flow cytometry. The data show that (1) at a low, physiologically relevant concentration (1 ng/mL), rapamycin impairs macropinocytosis and mannose receptor-mediated endocytosis; (2) the effects are independent of DC maturation and can be demonstrated specifically in immature CD11c(+) major histocompatibility complex (MHC) class II(lo) DCs by 3-color flow cytometry; (3) inhibition of endocytosis is not related to apoptotic cell death; and (4) molar excess of the structurally related molecule FK506 inhibits the actions of rapamycin. The inhibitory effects of rapamycin on DC endocytosis were confirmed in vivo. To our knowledge, this is the first report that a clinically relevant immunosuppressant inhibits DC endocytosis.

Animals↗
PubMed2002

Chemokines, their receptors, and transplant outcome.

Organ transplant rejection is mediated largely by circulating peripheral leukocytes induced to infiltrate the graft by various inflammatory stimuli. Of these, chemotactic cytokines called chemokines, expressed by inflamed graft tissues, as well as by early innate-responding leukocytes that infiltrate the graft, are responsible for the recruitment of alloreactive leukocytes. This report discusses the impact of these leukocyte-directing proteins on transplant outcome and novel therapeutic approaches for antirejection therapy based on targeting of chemokines and/or their receptors.

Animals↗
PubMed2002

Retroviral delivery of transforming growth factor-beta1 to myeloid dendritic cells: inhibition of T-cell priming ability and influence on allograft survival.

BACKGROUND: Transforming growth factor (TGF)-beta inhibits the maturation and function of antigen-presenting cells. Our purpose was to evaluate the impact of retroviral delivery of human TGF-beta1 to murine myeloid dendritic cell (DC) progenitors on (i) their in vitro properties, (ii) their in vivo function, and (iii) their influence on organ allograft survival. METHODS: C57BL10 (B10; H2b) bone marrow cells were lineage depleted and stimulated with granulocyte-macrophage colony-stimulating factor for 6 days. Replicating DC progenitors were transduced on days 2, 3, and 4 of culture by ecotropic retrovirus encoding human TGF-beta1 using centrifugal enhancement. Secretion of TGF-beta1 and other cytokines was quantified by enzyme immunoassay. Allogeneic C3H/HeJ (C3H; H2k) T-cell proliferative responses and generation of cytotoxic T lymphocytes in mixed leukocyte reaction were determined by [3H]thymidine incorporation and 51Cr release assays, respectively. DC migration was analyzed by immunohistochemistry, and their impact on survival of intra-abdominal heart transplants was determined. RESULTS: Maximal TGF-beta1 transduction efficiency was 60%. The TGF-beta-transduced DC showed pronounced impairment (>80%) of T-cell allostimulatory activity in vitro. After their IV injection, B10 TGF-beta-transduced DC (IAb+) were detected in T-cell areas of spleens of allogeneic C3H recipients. Splenic T-cell responses to donor alloantigens of mice that received TGF-beta-transduced DC were severely impaired. This was accompanied by marked inhibition of interleukin-2 and interferon-gamma production in response to restimulation with donor alloantigen. Survival of B10 cardiac allografts in C3H mice given B10 TGF-beta-transduced DC (2x106 IV, 7 days before transplantation), was extended modestly but significantly. CONCLUSION: Retroviral transduction of myeloid DC progenitors to overexpress TGF-beta is associated with marked impairment of their T-cell allostimulatory activity but with only modest prolongation of organ allograft survival.

Animals↗
PubMed2002

Cytokine gene polymorphisms in children successfully withdrawn from immunosuppression after liver transplantation.

BACKGROUND: Cytokine genetic polymorphisms have been associated with transplant outcome in some experimental and clinical studies, but the cytokine profile of patients who are clinically tolerant has not been investigated. AIM: Allelic variations in tumor necrosis factor (TNF)-alpha, interferon (INF)-gamma, transforming growth factor (TGF)-beta1, interleukin (IL)-6, and IL-10 were evaluated in patients successfully withdrawn from immunosuppression. METHODS: Pediatric liver transplant recipients who were successfully withdrawn from immunosuppression (n=12) or who are on minimal immunosuppression (n=7) were genotyped. A control group of liver recipients who required maintenance immunosuppression served as a control group (n=37). RESULTS: Compared to the control group, low TNF- alpha and high/intermediate IL-10 profiles were seen in all 12 children maintained off immunosuppression and in 6 of 7 children requiring minimal immunosuppression. CONCLUSION: Children successfully maintained off immunosuppression are more likely to have a genetic predisposition toward low TNF-alpha and high/intermediate IL-10 production. Children maintained on minimal immunosuppression exhibit a similar cytokine profile to those successfully weaned.

Adolescent↗
PubMed2002

Manipulation of dendritic cells as an approach to improved outcomes in transplantation.

At the time of organ transplantation, a variety of non-parenchymal cells are transplanted simultaneously with the allograft. Recognition of the importance of these cells as potential immunostimulatory cells lead to the concept of 'passenger leukocytes' as the principal instigators of rejection. Passenger leukocytes include interstitial dendritic cells (DCs) and blood-derived monocytes/macrophages. As investigators have discovered the significance of DCs in influencing graft outcome, so have they begun to determine the best ways to influence DCs themselves. This review discusses the role of DCs in transplantation and then focuses on three different approaches for manipulating DCs to improve allograft survival: (1) targeting of chemokines involved in DC migration, (2) pharmacological arrest of DC maturation, and (3) genetic engineering of DCs.

Animals↗
PubMed2002

Manipulation of dendritic cells for tolerance induction in transplantation and autoimmune disease.

Dendritic cells (DC) constitute a complex system of uniquely well-equipped antigen-presenting cells that initiate and regulate immune responses. Extensive recent studies have improved our understanding of DC development, differentiation, activation, and function. DC exist as distinct subsets that differ in their lineage affiliation, surface molecule expression, and biological function. These factors seem to determine the T-cell polarizing signals and type of T cell response-T helper 1, T helper 2, or T regulatory- induced by DC (1). Evidence has accumulated that DC play an important role in both central and peripheral tolerance via various mechanisms, including induction of T-cell anergy, immune deviation, T regulatory cell activity, and promotion of activated T-cell apoptosis. Although many of the details of the molecular basis of DC tolerogenicity have yet to be elucidated, emerging information suggests that costimulatory molecule deficiency, expression of death-inducing ligands (in particular Fas [CD95] ligand), microenvironmental factors (in particular anti-inflammatory/immunosuppressive cytokines), and inhibition of gene transcription regulatory proteins (e.g., nuclear factor-kappaB) can impart tolerogenic potential to DC (2). Manipulation of DC by control of their maturation and differentiation, or genetic engineering of these cells to express immunosuppressive molecules, offers potential for therapy of allograft rejection and autoimmune disease. In this brief overview, we outline principles and methods for generation of "tolerogenic" DC and outcomes that have been reported in experimental models. Space constraints limit literature citations.

Animals↗