Untersuchungen zur in vivo Depletion von regulatorischen T-Zellen und deren Einfluss auf die Immuntherapie des B16 Melanoms

Natürlich vorkommende regulatorische T-Zellen (Treg) sind essentiell an der Suppression von Effektor T-Zellen (Teff) beteiligt und verhindern dadurch beispielsweise Autoimmunkrankheiten. Außerdem wurde wiederholt beschrieben, dass Treg Immunreaktionen gegen verschiedene Tumore behindern. Diese Eigenschaft wurde dadurch deutlich, dass in Tiermodellen die Depletion von Treg vor der Tumorinokulation zu vermindertem Wachstum der Tumore führte. In Melanom-Patienten ist diese präventive Behandlung nicht durchführbar, da der Tumor in diesen Fällen bereits etabliert ist. Aus diesem Grund sollte im murinen B16 Modell untersucht werden, ob es möglich ist existierende Melanome mittels einer Kombination aus Treg-Depletion und Te_-Stimulation zu behandeln. Eine Depletion der Treg mittels Injektion des mAk PC61 vor der Tumorinokulation bewirkte die schon beschriebene Verminderung des Tumorwachstums. Im Gegensatz dazu hatte die Treg-Depletion zu späteren Zeitpunkten während der Tumorentwicklung (fünf oder zehn Tage nach der Tumorinokulation) ein beschleunigtes Wachstum zur Folge. Die Kombination von Treg-Depletion und therapeutischer Vakzinierung mit Tumorantigen-beladenen dendritischen Zellen (DC) bewirkte sogar ein sehr stark beschleunigtes Tumorwachstum. Die präventive Anwendung von PC61 führte zu niedrigeren Anzahlen von tumorassoziierten Treg und gleichzeitig zu einem Anstig der CD4+ und CD8+ Zellen in den Tumoren. Im Gegensatz dazu konnte bei therapeutischer Treg-Depletion kein Unterschied in der Infiltration der Tumore zwischen behandelten und nicht behandelten tumortragenden Mäusen festgestellt werden. Da durch therapeutische Injektion von PC61 und DC das Tumorwachstum stark beschleunigt wurde, war anzunehmen, dass der mAk CD25+ Teff depletiert. Zur Überprüfung dieser Annahme wurden Mäusen CFSE-gefärbte OVA-spezifische TCR-transgene CD4+ Zellen injiziert. Den Mäusen wurden OVA-beladene DC und gleichzeitig PC61 appliziert. Überraschender Weise waren weder die Anzahl der re-isolierten transgenen Zellen noch ihre Fähigkeit zu proliferieren und IL-2 zu produzieren in PC61-behandelten Mäusen reduziert sondern im Gegenteil erhöht. Diese Daten zeigen, dass die Beschleunigung des Tumorwachstums durch therapeutische Anwendung der Treg-Depletion nicht auf einer Ko-Depletion von Teff beruht. Vielmehr scheint die Entwicklung einer Tumorabstoßung abhängig von der Infiltration der Tumore durch CD4+ und CD8+ Zellen zu sein. Nur eine präventive Treg-Depletion verändert das Infiltrationsmuster des Tumors dahingehend, dass weniger Treg dafür aber mehr CD4+ und CD8+ Zellen einwandern. In fortgeschrittenen Tumorstadien scheint der Tumor ein Millieu zu schaffen, durch dass er den übertritt von T-Zellen und auch mAk ins Tumorgewebe verhindert

T Lymphocytes Contribute to the Control of Baseline Neural Precursor Cell Proliferation but Not the Exercise-Induced Up-Regulation of Adult Hippocampal Neurogenesis

Cross-talk between the peripheral immune system and the central nervous system is important for physiological brain health. T cells are required to maintain normal baseline levels of neural precursor proliferation in the hippocampus of adult mice. We show here that neither T cells, B cells, natural killer cells nor natural killer T cells are required for the increase in hippocampal precursor proliferation that occurs in response to physical exercise. In addition, we demonstrate that a subpopulation of T cells, regulatory T cells, is not involved in maintaining baseline levels of neural precursor proliferation. Even when applied at supraphysiological numbers, populations of both naive and stimulated lymphocytes had no effect on hippocampal precursor proliferation in vitro. In addition, physical activity had no effect on peripheral immune cells in terms of distribution in the bone marrow, lymph nodes or spleen, activation state or chemokine receptor (CXCR4 and CCR9) expression. Together these results suggest that lymphocytes are not involved in translating the peripheral effects of exercise to the neurogenic niche in the hippocampus and further support the idea that the exercise-induced regulation of adult neurogenesis is mechanistically distinct from its baseline control

Inducible IL-7 Hyperexpression Influences Lymphocyte Homeostasis and Function and Increases Allograft Rejection

The IL-7/IL-7R pathway is essential for lymphocyte development and disturbances in the pathway can lead to immune deficiency or T cell mediated destruction. Here, the effect of transient hyperexpression of IL-7 was investigated on immune regulation and allograft rejection under immunosuppression. An experimental in vivo immunosuppressive mouse model of IL-7 hyperexpression was developed using transgenic mice (C57BL/6 background) carrying a tetracycline inducible IL-7 expression cassette, which allowed the temporally controlled induction of IL-7 hyperexpression by Dexamethasone and Doxycycline treatment. Upon induction of IL-7, the B220+ c-kit+ Pro/Pre-B I compartment in the bone marrow increased as compared to control mice in a serum IL-7 concentration-correlated manner. IL-7 hyperexpression also preferentially increased the population size of memory CD8+ T cells in secondary lymphoid organs, and reduced the proportion of CD4+Foxp3+ T regulatory cells. Of relevance to disease, conventional CD4+ T cells from an IL-7-rich milieu escaped T regulatory cell-mediated suppression in vitro and in a model of autoimmune diabetes in vivo. These findings were validated using an IL-7/anti-IL7 complex treatment mouse model to create an IL-7 rich environment. To study the effect of IL-7 on islet graft survival in a mismatched allograft model, BALB/c mice were rendered diabetic by streptozotocin und transplanted with IL-7-inducible or control islets from C57BL/6 mice. As expected, Dexamethasone and Doxycycline treatment prolonged graft median survival as compared to the untreated control group in this transplantation mouse model. However, upon induction of local IL-7 hyperexpression in the transplanted islets, graft survival time was decreased and this was accompanied by an increased CD4+ and CD8+ T cell infiltration in the islets. Altogether, the findings show that transient elevations of IL-7 can impair immune regulation and lead to graft loss also under immune suppression

Affinity for self antigen selects T_reg cells with distinct functional properties

The manner in which regulatory T cells (Treg cells) control lymphocyte homeostasis is not fully understood. We identified two Treg cell populations with differing degrees of self-reactivity and distinct regulatory functions. We found that GITR(hi)PD-1(hi)CD25(hi) (Triple(hi)) Treg cells were highly self-reactive and controlled lympho-proliferation in peripheral lymph nodes. GITR(lo)PD-1(lo)CD25(lo) (Triple(lo)) Treg cells were less self-reactive and limited the development of colitis by promoting the conversion of CD4(+) Tconv cells into induced Treg cells (iTreg cells). Although Foxp3-deficient (Scurfy) mice lacked Treg cells, they contained Triple(hi)-like and Triple(lo)-like CD4(+) T cells zsuper< T cells infiltrated the skin, whereas Scurfy Triple(lo)CD4(+) T cells induced colitis and wasting disease. These findings indicate that the affinity of the T cell antigen receptor for self antigen drives the differentiation of Treg cells into distinct subsets with non-overlapping regulatory activities

On the use of multi-criteria decision analysis to formally integrate community values into ecosystem-based freshwater management

Freshwater ecosystems are essential to peoples’ economic, cultural, and social wellbeing, yet are still among the most threatened ecosystems on the planet. Consequently, a plethora of recent regulations and policies seek to halt the loss of, restore, or safeguard freshwaters, their biodiversity, and the ecosystem services they provide. Ecosystem-based management (EBM), an approach that considers human society as an integral part of ecosystems, is increasingly being promoted to help meet this challenge. EBM involves an overarching regulatory framework and local solutions with trade-offs and compromises - factors that make decision processes complex, but also provide the means for combining top-down regulation with bottom-up priorities into collaborative management strategies. Although stakeholder participation is encouraged in most modern freshwater management, community values are often largely neglected. Here, we introduce a well-known participatory decision support framework based on multi-criteria decision analysis (MCDA) to operationalize EBM and promote community-inclusive decision-making in freshwater management. We explain the different steps that this approach comprises which lead to the prioritisation of a management strategy in a collaborative way. We also show how cultural values that inherently embed strong links between the environment and people, can be used together with typical ecological and socio-economic values. We illustrate the MCDA-based EBM-approach for New Zealand, one of the few countries in which regional freshwater management is mandated to uphold environmental quality standards, while safeguarding local community values and ecosystem services. Finally, we discuss some of the challenges which are increasingly emerging as a result of mandated community collaboration in environmental management

Dendritic Cell-Targeted Pancreatic β-Cell Antigen Leads to Conversion of Self-Reactive CD4+ T Cells Into Regulatory T Cells and Promotes Immunotolerance in NOD Mice

Studies employing T cell receptor transgenic T cells have convincingly shown that selective delivery of non-self model antigens to DEC-205+ dendritic cells (DCs) in the steady-state can induce Foxp3-expressing CD4+CD25+ regulatory T (Treg) cells from conventional CD4+CD25-Foxp3- T cells. Although of considerable clinical interest, the concept of DC-targeted de novo generation of antigen-specific Treg cells has not yet been evaluated for self-antigens and self-reactive CD4+ T cells in the non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D). Here, we show in proof-of-principle experiments that targeting a mimotope peptide to the endocytic receptor DEC-205 on DCs in NOD mice induces efficient conversion of pancreatic β-cell-reactive BDC2.5 CD4+ T cells into long-lived Foxp3+ Treg cells. Of note, conversion efficiency in normoglycemic and hyperglycemic mice with early diabetes onset was indistinguishable. While de novo generation of BDC2.5 Treg cells did not interfere with disease progression, anti-DEC-205-mediated targeting of whole proinsulin in prediabetic NOD mice substantially reduced the incidence of diabetes. These results suggest that promoting antigen-specific Treg cells in vivo might be a feasible approach towards cellular therapy in T1D

Vagaries of fluorochrome reporter gene expression in Foxp3+ regulatory T cells.

CD4(+)CD25(+) regulatory T (Treg) cell lineage commitment and expression of the transcription factor Foxp3 can be induced at the CD4(+)CD8(+) double-positive (DP) and CD4(+)CD8(?) single-positive stages of thymic development, as well as in postthymic CD4(+) T cells in peripheral lymphoid tissues. The availability of transgenic mice with Foxp3-dependent fluorochrome reporter gene expression has greatly facilitated studies on the intra- and extrathymic generation of murine Foxp3(+) Treg cells. Here, we performed a comparative analysis of thymic Treg cell development and peripheral compartments of mature Treg cells in various transgenic strains with gene targeted and bacterial artificial chromosome (BAC)-driven Foxp3-fluorochrome expression. These studies revealed a relative deficiency of Foxp3(+) DP thymocytes selectively in mice with targeted insertion of the fluorochrome reporter gene coding sequence into the endogenous Foxp3 gene. While Foxp3 BAC-driven fluorochrome expression in ex vivo CD4(+) T cells was found to faithfully reflect Foxp3 protein expression, we provide evidence that Foxp3 BAC transgenesis can result in sizable populations of Foxp3(+) Treg cells that lack fluorochrome reporter expression. This could be attributed to both timely delayed up-regulation of BAC expression in developing Treg cells and the accumulation of peripheral Foxp3(+) Treg cells with continuous transcriptional inactivity of the Foxp3 BAC transgene

Myelin-specific T helper 17 cells promote adult hippocampal neurogenesis through indirect mechanisms [version 2; referees: 1 approved, 2 approved with reservations]

CD4+ T cells provide a neuro-immunological link in the regulation of adult hippocampal neurogenesis, but the exact mechanisms underlying enhanced neural precursor cell proliferation and the relative contribution of different T helper (Th) cell subsets have remained unclear. Here, we explored the pro-proliferative potential of interleukin 17-producing T helper (Th17) cells, a developmentally and functionally distinct Th cell subset that is a key mediator of autoimmune neurodegeneration. We found that base-line proliferation of hippocampal precursor cells in a T cell-deficient mouse model of impaired hippocampal neurogenesis can be restored upon adoptive transfer with homogeneous Th17 populations enriched for myelin-reactive T cell receptors (TCR). In these experiments, enhanced proliferation was independent of direct interactions of infiltrating Th17 cells with precursor cells or neighboring cells in the hippocampal neurogenic niche. Complementary studies in immunocompetent mice identified several receptors for Th17 cell-derived cytokines with mRNA expression in hippocampal precursor cells and dentate gyrus tissue, suggesting that Th17 cell activity in peripheral lymphoid tissues might promote hippocampal neurogenesis through secreted cytokines

Foxp3+ Regulatory T Cells in Mouse Models of Type 1 Diabetes

Studies on human type 1 diabetes (T1D) are facilitated by the availability of animal models such as nonobese diabetic (NOD) mice that spontaneously develop autoimmune diabetes, as well as a variety of genetically engineered mouse models with reduced genetic and pathogenic complexity, as compared to the spontaneous NOD model. In recent years, increasing evidence has implicated CD4+CD25+ regulatory T (Treg) cells expressing the transcription factor Foxp3 in both the breakdown of self-tolerance and the restoration of immune homeostasis in T1D. In this paper, we provide an overview of currently available mouse models to study the role of Foxp3+ Treg cells in the control of destructive β cell autoimmunity, including a novel NOD model that allows specific and temporally controlled deletion of Foxp3+ Treg cells