Biomedical subjects

Herman Waldmann

Publications and source records attributed to Herman Waldmann.

At least 37 records · Page 2Linked to original sources

PubMed2005

In vivo kinetics of GITR and GITR ligand expression and their functional significance in regulating viral immunopathology.

This report evaluates the role of interaction between glucocorticoid-induced tumor necrosis factor receptor (GITR) and GITR ligand (GITR-L) in the immuno-inflammatory response to infection with herpes simplex virus (HSV). Both GITR and GITR-L were transiently upregulated after ocular HSV infection, on antigen-specific T cells and antigen-presenting cells, respectively, in the draining lymph node (DLN). In addition, virus-specific T-cell responses in the DLN and spleen were enhanced by anti-GITR antibody treatment, an outcome expected to result in more severe inflammatory lesions. Intriguingly, the treatment resulted in significantly diminished T-cell-mediated ocular lesions. The explanation for these findings was that anti-GITR antibody treatment caused a reduced production of ocular MMP-9, a molecule involved in ocular angiogenesis, an essential step in the pathogenesis of herpetic keratitis. Our results are the first observations to determine in vivo kinetics of GITR and GITR-L expression after virus infection, and they emphasize the role of GITR-GITR-L interaction to regulate virus-induced immuno-inflammatory lesions.

Animals↗

PubMed2005

CD8+ lymphocytes do not mediate protection against acute superinfection 20 days after vaccination with a live attenuated simian immunodeficiency virus.

In order to test the hypothesis that CD8+ cytotoxic T lymphocytes mediate protection against acute superinfection, we depleted >99% of CD8+ lymphocytes in live attenuated simian immunodeficiency virus macC8 (SIVmacC8) vaccinees from the onset of vaccination, maintained that depletion for 20 days, and then challenged with pathogenic, wild-type SIVmacJ5. Vaccinees received 5 mg per kg of humanized anti-CD8 monoclonal antibody (MAb) 1 h before inoculation, followed by the same dose again on days 3, 7, 10, 13, and 17. On day 13, peripheral CD8+ T lymphocytes were >99% depleted in three out of four anti-CD8 MAb-treated vaccinees. At this time attenuated SIVmacC8 viral RNA loads in anti-CD8 MAb-treated vaccinees were significantly higher than control vaccinees treated contemporaneously with nonspecific human immunoglobulin. Lymphoid tissue CD8+ T lymphocyte depletion was >99% in three out of four anti-CD8 MAb-treated vaccinees on the day of wild-type SIVmacJ5 challenge. All four control vaccinees and three out of four anti-CD8 MAb-treated vaccinees were protected against detectable superinfection with wild-type SIVmacJ5. Although superinfection with wild-type SIVmacJ5 was detected at postmortem in a single anti-CD8 MAb-treated vaccinee, this did not correlate with the degree of preceding CD8+ T lymphocyte depletion. Clearance of attenuated SIVmacC8 viremia coincided with recovery of normal CD8+ T lymphocyte counts between days 48 and 76. These results support the view that cytotoxic T lymphocytes are important for host-mediated control of SIV primary viremia but do not indicate a central role in protection against acute superinfection conferred by inoculation with live attenuated SIV.

Animals↗

PubMed2005

Cell replacement therapy and the evasion of destructive immunity.

The potential of human embryonic stem (ES) cells to meet the growing demand for cell types and tissues for the treatment of chronic and degenerative diseases has been widely acclaimed. Nevertheless, their use in cell replacement therapy poses a number of significant challenges, not least of which is their subsequent rejection by the recipient's immune system. Here we explore the extent of the immunological barriers encountered and evaluate the potential of different approaches to overcoming these issues of which somatic nuclear transfer (SNT) and the induction of transplanation tolerance are currently the most promising.

Animals↗

PubMed2005

Autoimmune diabetes onset results from qualitative rather than quantitative age-dependent changes in pathogenic T-cells.

Diabetogenic T-cells can be detected in pre-diabetic nonobese diabetic (NOD) mice after transfer in NOD-SCID recipients. Here we demonstrate that 6-week-old pre-diabetic NOD mice, >2 months before disease onset, already harbor pathogenic T-cells in equal numbers to overtly diabetic animals. The delay in diabetes appearance is explained by the presence of regulatory CD4+ CD25+ T-cells that control diabetogenic effectors and that are, in our hands, transforming growth factor (TGF)-beta-dependent. Our present results suggest, however, that diabetes onset is only partly explained by a decline in this regulatory T-cell activity. Another major factor appears to be the progressive resistance of diabetogenic cells to TGF-beta-dependent mediated inhibition. We propose that progression to overt disease correlates with the pathogenic T-cell's escape from TGF-beta-dependent T-cell-mediated regulation.

Adoptive Transfer↗

PubMed2004

Induction of immunological tolerance/hyporesponsiveness in baboons with a nondepleting CD4 antibody.

Tolerance induction with anti-CD4 Abs is well established in rodent transplant and autoimmune disease models, but has yet to be demonstrated in non-human primates or in clinical studies. In retrospect, failure of anti-CD4 Abs to induce tolerance in primates may be technical, a consequence of insufficient dosing and Ab properties influencing immunogenicity and cell depletion. To circumvent these possible limitations, we constructed a novel anti-CD4 mAb, TRX1, humanized to reduce immunogenicity and Fc-modified to prevent cell depletion. Using equine immune globulin (equine Ig) as a model Ag, we examined the tolerance-inducing capacity of TRX1 in baboons. During the induction phase, TRX1 inhibited the humoral response to equine Ig in a dose-dependent manner, with complete suppression of response at the highest dose tested (40 mg/kg). Upon challenge, anti-equine Ig responses were generated in baboons treated with 1 and 10 mg/kg doses of TRX1 and in control animals. In higher dosing cohorts (20 and 40 mg/kg), however, the immune response to equine Ig was modulated in seven of nine animals, including complete unresponsiveness to Ag challenges in two animals. Five of nine were hyporesponsive to equine Ig, generating titers 50- to 250-fold lower than control groups. Repeated challenge resulted in titers falling to baseline or near baseline, with two of five hyporesponsive animals becoming unresponsive to Ag. All animals responded to neoantigen immunization, indicating that the modified response to equine Ig was Ag specific. These studies demonstrate that anti-CD4 Ab-mediated, Ag-specific tolerance can be achieved in baboons without long term immune suppression.

Amino Acid Substitution↗

PubMed2004

Specific subsets of murine dendritic cells acquire potent T cell regulatory functions following CTLA4-mediated induction of indoleamine 2,3 dioxygenase.

Murine dendritic cells (DCs) expressing indoleamine 2,3 dioxygenase (IDO) catabolize tryptophan and can suppress T cell responses elicited in vivo. Here, we identify specific subsets of splenic (CD11c+) dendritic cells competent to mediate IDO-dependent T cell suppression following CTLA4-mediated ligation of B7 molecules. IDO-competent DC subsets acquired potent and dominant T cell suppressive properties as a consequence of IDO up-regulation, as they blocked the ability of T cells to respond to other stimulatory DCs in the same cultures. Soluble CTLA4 (CTLA4-Ig) and cloned CTLA4+ regulatory T cells (Tr1D1) up-regulated IDO selectively in DC subsets co-expressing B220 or CD8alpha. The ability of Tr1D1 T cells to suppress CD8+ T cell responses was completely dependent on their ability to induce tryptophan catabolism in DCs. Selective IDO up-regulation in DCs did not inhibit T cell activation, but prevented T cell clonal expansion due to rapid death of activated T cells. T cell responses were restored by genetic or pharmacologic inhibition of IDO enzyme activity, or by adding excess tryptophan. DCs from interferon gamma (IFNgamma)-receptor-deficient mice were effective in promoting IDO-dependent T cell suppression following CTLA4-Ig exposure in vivo, indicating that IFNgamma signaling was not necessary for IDO up-regulation in this model. These findings suggest that IDO-competent DCs provide a regulatory bridge, mediated by CTLA4-B7 engagement, between certain regulatory T cell subsets and naive responder T cells.

Abatacept↗

PubMed2004

Exploiting tolerance processes in transplantation.

The full potential of organ transplantation has not yet been realized because of the hazards associated with the long-term use of immunosuppressive drugs. Modern research into mechanisms of immune tolerance offers the promise of reprogramming the immune system, so as to harness the body's natural tolerance mechanisms in the service of graft acceptance. This would allow the minimization of immunosuppressive treatment and offers the prospect of eventually weaning transplant recipients off their drugs.

Animals↗

PubMed2004

Donor-specific transplantation tolerance: the paradoxical behavior of CD4+CD25+ T cells.

To investigate the antigen specificity of regulatory T cells capable of preventing transplant rejection, we have developed two different strategies to achieve tolerance to fully mismatched skin grafts in euthymic mice. A combination of nondepleting Abs targeting CD4, CD8, and CD154 (CD40 ligand) induces dominant transplantation tolerance to fully mismatched skin allografts. Such tolerance is antigen-specific, mediated by regulatory T cells, and can be extended through linked suppression to naïve lymphocytes. The same protocol, when combined with allogeneic bone marrow, enables the development of mixed hematopoietic chimerism and deletional tolerance. Although we cannot exclude that some regulatory T cells may persist in chimeric mice, these cells are insufficient to mediate linked suppression. CD4(+)CD25(+) T cells, whether taken from naïve mice or from mice tolerized through either treatment protocol, were always able to prevent rejection of skin grafts by naïve CD4(+) T cells, and did so with no demonstrable specificity for the tolerizing donor antigens. Such data question whether CD4(+)CD25(+) regulatory T cells alone can account for the antigen specificity of dominant transplantation tolerance.

Animals↗

PubMed2004

Generation of anergic and regulatory T cells following prolonged exposure to a harmless antigen.

Regulatory CD4(+) T cells are known to develop during the induction of donor-specific peripheral tolerance to transplanted tissues; it is proposed that such tolerance is a consequence of persistent, danger-free stimulation by Ag. To test this hypothesis, male RAG-1(-/-) mice were recolonized with small numbers of monospecific CD4(+) T cells specific for the male H-2E(k)-restricted Ag Dby. After 6 wk in the male environment, the monospecific CD4(+) T cells, having recolonized the host, had become anergic to stimulation in vitro and had acquired a regulatory capacity. CD4(+) T cells in these mice expressed higher levels of CTLA-4 and glucocorticoid-induced TNF-related receptor than naive CD4(+) T cells, but only 3% of the recolonizing cells were CD25(+) and did not express significant foxP3 mRNA. In vivo, these tolerant T cells could censor accumulation of, and IFN-gamma production by, naive T cells, with only a slight inhibition of proliferation. This suppressive effect was not reversed by the addition of fresh bone marrow-derived male dendritic cells. These results suggest that persistent exposure to Ag in conditions that fail to evoke proinflammatory stimuli leads to the development of T cells that are both anergic and regulatory.

Adoptive Transfer↗

PubMed2004

Induction of foxP3+ regulatory T cells in the periphery of T cell receptor transgenic mice tolerized to transplants.

Transplantation tolerance can be induced in mice by grafting under the cover of nondepleting CD4 plus CD8 or CD154 mAbs. This tolerance is donor Ag specific and depends on a population of CD4(+) regulatory T cells that, as yet, remain poorly defined in terms of their specificity, origin, and phenotype. Blocking of the Ag-specific response in vitro with an anti-CD4 mAb allowed T cells from monospecific female TCR-transgenic mice against the male Ag Dby, presented by H-2E(k), to express high levels of foxP3 mRNA. foxP3 induction was dependent on TGF-beta. The nondepleting anti-CD4 mAb was also able to induce tolerance in vivo in such monospecific TCR-transgenic mice, and this too was dependent on TGF-beta. As in conventional mice, acquired tolerance was dominant, such that naive monospecific T cells were not able to override tolerance. Splenic T cells from tolerant mice proliferated normally in response to Ag, and secreted IFN-gamma and some IL-4, similar to control mice undergoing primary or secondary graft rejection. High levels of foxP3 mRNA, and glucocorticoid-induced TNFR superfamily member 18 (GITR)(+) CD25(+) T cells were found within the tolerated skin grafts of long-term tolerant recipients. These data suggest that regulatory T cells maintaining transplantation tolerance after CD4 Ab blockade can be induced de novo through a TGF-beta-dependent mechanism, and come to accumulate in tolerated grafts.

Amino Acid Sequence↗

PubMed2004

Blood concentrations of alemtuzumab and antiglobulin responses in patients with chronic lymphocytic leukemia following intravenous or subcutaneous routes of administration.

Alemtuzumab is a humanized anti-CD52 antibody licensed for refractory B-cell chronic lymphocytic leukemia (B-CLL), when given intravenously at 30 mg thrice weekly. However, the intravenous route is associated with infusion-related reactions and is inconvenient. We measured blood concentrations in 30 relapsed patients treated with intravenous alemtuzumab and in 20 patients from a previously untreated group who received similar doses subcutaneously. Highest trough samples in the intravenous group were less than 0.5 microg/mL to 18.3 microg/mL (mean 5.4 microg/mL). The cumulative dose required to reach 1.0 microg/mL was 13 mg to 316 mg (mean 90 mg). Higher blood concentrations correlated with the achievement of better clinical responses and minimal residual disease. The highest measured concentrations in the subcutaneous group were similar (0.6 microg/mL to 24.8 microg/mL, mean 5.4 microg/mL). However, the cumulative dose to reach 1.0 microg/mL was higher: 146 mg to 1106 mg (mean 551 mg). No antiglobulin responses were detected in 30 patients given intravenous alemtuzumab whereas 2 of 32 patients given subcutaneous alemtuzumab made substantial anti-idiotype responses. Thus, subcutaneous alemtuzumab achieved concentrations similar to those for intravenous alemtuzumab, although with slightly higher cumulative doses. Subcutaneous alemtuzumab is more convenient and better tolerated but may be associated with some patients forming anti-alemtuzumab antibodies, particularly those patients who were previously untreated.

Alemtuzumab↗

PubMed2004

IL-10-conditioned dendritic cells, decommissioned for recruitment of adaptive immunity, elicit innate inflammatory gene products in response to danger signals.

Dendritic cells (DCs) are the professional APCs of the immune system, enabling T cells to perceive and respond appropriately to potentially dangerous microbes, while also being able to maintain T cell tolerance toward self. In part, such tolerance can be determined by IL-10 released from certain types of regulatory T cells. IL-10 has previously been shown to render DCs unable to activate T cells and it has been assumed that this process represents a general block in maturation. Using serial analysis of gene expression, we show that IL-10 pretreatment of murine bone marrow-derived DCs alone causes significant changes in gene expression. Furthermore, these cells retain the ability to respond to Toll-like receptor agonists, but in a manner skewed toward the selective induction of mediators known to enhance local inflammation and innate immunity, among which we highlight a novel CXCR2 ligand, DC inflammatory protein-1. These data suggest that, while the presence of a protolerogenic and purportedly anti-inflammatory agent such as IL-10 precludes DCs from acquiring their potential as initiators of adaptive immunity, their ability to act as initiators of innate immunity in response to Toll-like receptor signaling is enhanced.

Amino Acid Motifs↗

PubMed2004

Neutralizing tumor necrosis factor activity leads to remission in patients with refractory noninfectious posterior uveitis.

OBJECTIVE: To evaluate the efficacy and safety of tumor necrosis factor (TNF) inhibition with the p55 TNF receptor fusion protein (TNFr-Ig) for severe sight-threatening noninfectious posterior segment intraocular inflammation. METHODS: Seventeen patients with refractory noninfectious posterior segment intraocular inflammation received TNFr-Ig by intravenous infusion in this nonrandomized, open-label, pilot study. The primary outcome measure was logMAR visual acuity. Secondary outcome measures were binocular indirect ophthalmoscopy score, cystoid macular edema, adverse effects, and vision-related (visual core module 1) and health-related (36-Item Short-Form Health Survey) quality of life. RESULTS: Within 1 month of TNFr-Ig therapy, 9 patients (53%) achieved at least a 2-line improvement in visual acuity, 8 (57%) of 14 patients with vitreous haze before treatment achieved an improvement in binocular indirect ophthalmoscopy score to 0, and macular edema resolved in 5 (56%) of 9 affected patients. Twelve (71%) of the patients achieved complete cessation of intraocular inflammation following TNFr-Ig therapy. A reduction in concomitant immunosuppression was possible for 11 patients (65%) following TNFr-Ig therapy. However, all but 1 patient required continuing adjuvant therapy during the response to TNFr-Ig, which had a median duration of 3 months. Adverse effects included mild infusion reactions in 3 patients and transient lymphocytopenia in 2 patients. CONCLUSION: Therapy with TNFr-Ig was safe and effective for treating patients with sight-threatening noninfectious posterior segment intraocular inflammation resistant to conventional immunotherapy, but adjuvant immunosuppression and repeat infusions would be required to maintain long-term remission.

Adult↗

PubMed2004

Embryonic stem cells and the challenge of transplantation tolerance.

Isolated from early blastocysts, embryonic stem (ES) cells capture the brief moment of pluripotency in the developing embryo, as evidenced by their differentiation into many somatic cell types in vitro. Although these properties might help meet the growing demand for 'spare parts' to replace diseased or worn-out tissues, their use in so-called cell replacement therapy (CRT) poses several challenges, not least of which is the prevention of their subsequent rejection. Here we explore the notion that ES cells might spawn cell types necessary for the treatment of disease while acting as a plentiful source of hematopoietic stem cells (HSCs) or terminally differentiated dendritic cells (DCs) that might facilitate the induction of transplantation tolerance to the replacement tissues.

Animals↗

PubMed2004

Regulatory T cells and organ transplantation.

Empirical studies attempting to explain tolerance to transplanted tissues have demonstrated a regulatory role for CD4+ T-cells. We here propose that regulatory T-cells mediating transplantion tolerance comprise two sets which can functionally complement each other. The CD4+CD25+ "natural regulator" arises in the thymus, and is preoccupied with self-antigens expressed at sites of inflammation. The second, comprising both CD4+CD25+ (FoxP3+) and CD4+CD25- Tr1-like cells are induced by persistent danger-free antigen in the periphery. The role of these cells is to moderate immune responses to prevent tissue destruction while allowing microbial elimination.

Animals↗

PubMed2004

Induction of dominant transplantation tolerance by an altered peptide ligand of the male antigen Dby.

T cell reactivity to minor histocompatibility (mH) antigens is responsible for rejection of HLA-matched allografts, limiting the effectiveness of transplantation for the treatment of end-stage organ failure. The deadbox gene Dby is located on the Y chromosome and encodes an mH antigen that prompts rejection of male tissues by female mice. Establishing a network of regulatory T (T(reg)) cells that is capable of coercing naive cells to adopt a tolerant phenotype offers an attractive strategy for immune intervention in such deleterious immune responses. While various approaches have successfully induced a dominant form of transplantation tolerance, they share the propensity to provoke chronic, incomplete activation of T cells. By identifying the T cell receptor (TCR) contact sites of the dominant epitope of the Dby gene product, we have designed an altered peptide ligand (APL) that delivers incomplete signals to naive T cells from A1 infinity RAG1(-/-) mice that are transgenic for a complementary TCR. Administration of this APL to female transgenic mice polarizes T cells toward a regulatory phenotype, securing a form of dominant tolerance to male skin grafts that is capable of resisting rejection by naive lymphocytes. Our results demonstrate that incomplete signaling through the TCR may establish a network of T(reg) cells that may be harnessed in the service of transplantation tolerance.

Animals↗

PubMed2003

Mouse glucocorticoid-induced tumor necrosis factor receptor ligand is costimulatory for T cells.

Recently, agonist antibodies to glucocorticoid-induced tumor necrosis factor receptor (GITR) (tumor necrosis factor receptor superfamily 18) have been shown to neutralize the suppressive activity of CD4+CD25+ regulatory T cells. It was anticipated that this would be the role of the physiological ligand. We have identified and expressed the gene for mouse GITR ligand and have confirmed that its interaction with GITR reverses suppression by CD4+CD25+ T cells. It also, however, provides a costimulatory signal for the antigen-driven proliferation of naïve T cells and polarized T helper 1 and T helper 2 clones. RT-PCR and mAb staining revealed mouse GITR ligand expression in dendritic cells, macrophages, and B cells. Expression was controlled by the transcription factor NF-1 and potentially by alternative splicing of mRNA destabilization sequences.

Alternative Splicing↗

PubMed2003

Stable lines of genetically modified dendritic cells from mouse embryonic stem cells.

BACKGROUND: The capacity to activate naïve T cells sets dendritic cells (DCs) apart from other antigen-presenting cells, making them attractive targets for immune intervention during deleterious immune responses. The inherent resistance of terminally differentiated DCs to conventional strategies for genetic modification has, however, greatly limited our understanding of the molecular mechanisms underlying their function. METHODS AND RESULTS: We report the derivation of long-term cultures of untransformed DCs, uniformly expressing a defined mutant phenotype by the directed differentiation of cloned embryonic stem cells, stably transfected with a reporter gene. Introduction of the gene encoding enhanced green fluorescent protein into pluripotent stem cells demonstrated no observable impact on the phenotype, immunogenicity, or capacity for maturation of DCs differentiated from them. CONCLUSIONS: The production of unlimited numbers of mutant DCs from genetically modified embryonic stem cells paves the way for the systematic elucidation of gene function in this cell type and the rational design of DCs for use in immunotherapy.

Animals↗