Role of CD8 T cell subsets in the pathogenesis of multiple sclerosis

AbstractMultiple sclerosis (MS) is an immune-mediated disease of the central nervous system leading to demyelination and axonal/neuronal loss. Cumulating evidence points to a key role for CD8 T cells in this disabling disease. Oligoclonal CD8 T cells reside in demyelinating plaques where they are likely to contribute to tissue destruction. Histopathological analyses and compelling observations from animal models indicate that cytotoxic CD8 T cells target neural cell populations with the potential of causing lesions reminiscent of MS. However, CD8 T cell differentiation results in several subsets of effector CD8 T cells that could be differentially implicated in the mechanisms contributing to tissue damage. Moreover CD8 regulatory T cells arise as important populations involved in restoring immune homoeostasis and in maintaining immune privileged sites. Here we examine the current literature pertaining to the role of CD8 effector and regulatory T cell subsets in the pathogenesis of MS

Thimet oligopeptidase (EC 3.4.24.15) key functions suggested by knockout mice phenotype characterization

Thimet oligopeptidase (THOP1) is thought to be involved in neuropeptide metabolism, antigen presentation, neurodegeneration, and cancer. Herein, the generation of THOP1 C57BL/6 knockout mice (THOP1(-/-)) is described showing that they are viable, have estrus cycle, fertility, and a number of puppies per litter similar to C57BL/6 wild type mice (WT). In specific brain regions, THOP1(-/-) exhibit altered mRNA expression of proteasome beta5, serotonin 5HT2a receptor and dopamine D2 receptor, but not of neurolysin (NLN). Peptidomic analysis identifies differences in intracellular peptide ratios between THOP1(-/-) and WT mice, which may affect normal cellular functioning. In an experimental model of multiple sclerosis THOP1(-/-) mice present worse clinical behavior scores compared to WT mice, corroborating its possible involvement in neurodegenerative diseases. THOP1(-/-) mice also exhibit better survival and improved behavior in a sepsis model, but also a greater peripheral pain sensitivity measured in the hot plate test after bradykinin administration in the paw. THOP1(-/-) mice show depressive-like behavior, as well as attention and memory retention deficits. Altogether, these results reveal a role of THOP1 on specific behaviors, immune-stimulated neurodegeneration, and infection-induced inflammation

Amelioration of Experimental Autoimmune Encephalomyelitis Using the Myelin Oligodendrocyte Glycoprotein35-85 Peptide

Multiple sclerosis (MS) is a chronic debilitating disease affecting the central nervous system (CNS) in humans. Experimental autoimmune encephalomyelitis (EAE) remains the primary animal model of MS. MS/EAE are considered to be autoimmune diseases mediated by CD4+ T helper (TH) cells. The role of B cells and antibody is under debate. Previous studies established B cell dependent (induced with recombinant myelin oligodendrocyte glycoprotein, [rMOG]) and B cell independent (induced with the MOG35-55 peptide) animal models of EAE. The identification of a unique B cell epitope (MOG amino acids [aa] 46-85) preceding the identified protective epitope (MOG61-85) led to the hypothesis that these antibodies against MOGaa46-85 were important in epitope selection in the rMOG model of EAE. Co-immunization of WT and B cell deficient (B cell-/-) mice with MOG35-55 and MOG61-85 resulted in abrogation (B cell-/- mice) or amelioration (WT mice) of EAE. Thus, mice were immunized with MOG35-85 peptide and observed for EAE induction. Absence of EAE in WT and B cell-/- mice was observed. These results confirmed the protective nature of the MOG61-85 peptide but did not support a role for antibodies to MOG¬46-85 in the selection of the protective epitope. Mechanistic studies revealed decreased production of the pro-inflammatory cytokines, interferon (INF) γ and interleukin (IL) 17, when immune cells were primed to MOG61-85 in vivo. Furthermore, using IL10 deficient (IL10-/-) mice, it was demonstrated that IL10 was important in EAE incidence, but not in disease severity, in the presence of the MOG61-85 epitope. Flow cytometric analysis of spleen cells from these mice demonstrated an increase in the number of T cells expressing FoxP3 expression and an increase in the CD4+ CD25+ T cell population, but a comparable level of CD4+ T regulatory (Treg) cell population. In addition no changes could be detected in the CD8+ T cell population. These experiments provide a deeper understanding of the B cell-dependent, rMOG model of EAE, demonstrating the role of the MOG61-85 epitope in down-regulating the pro-inflammatory response leading to protection from EAE, perhaps mediated by CD4+ Treg cells

Devic mouse: a spontaneous double-transgenic mouse model of human opticospinal multiple sclerosis and autoimmune T- B cell cooperation

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS). Myelin antigen(s) specific T cells, B cells, and antibodies are thought to play a role in the pathogenesis of MS. While the influence of autoantigenspecific CD4+ T cells has been extensively studied in animal models, the relevance of autoantigen specific B cells and their interactions with pathogenic T cells are largely unknown. The original aim of the present study was to create a new mouse model with which to investigate the interaction of myelin autoantigen specific B and T cells and their role in MS pathogenesis. The study was further expanded to analyze the nature and triggers of spontaneous disease and similarity of the mouse lesion pattern to that in human disease. The double-transgenic mouse (“Devic mouse”) strain presented here contains myelin oligodendrocyte glycoprotein (MOG)-specific T as well as B cells. A significant proportion (>50%) of these mice showed spontaneous experimentalautoimmune encephalomyelitis (EAE)-like disease at a young age. In contrast, all single transgenic littermates were free of clinical disease. Spontaneous EAE requires both MOG-specific T and B cells, since the breeding of MOG-specific Ig heavy chain knock-in mice with ovalbumin specific T cell receptor (TCR) transgenic mice did not develop any disease. Histological analysis of the CNS of affected mice revealed restricted localization of lesions in the spinal cord and optic nerves as well as severe demyelination and axonal damage that spared brain and cerebellum. The inflammatory infiltrates were predominantly composed of macrophages and CD4+ T cells, but occasionally also eosinophils. This peculiar localization of the demyelinating lesions and infiltration profile differ from classic EAE and is reminiscent of Devic’s neuromyelitis optica, a variant of classic MS in humans. It is not well understood what triggers the initiation of spontaneous EAE. The microbial environment does not significantly affect the clinical disease. Stimulation of the innate immune system with toll-like receptor (TLR) ligands or depletion of putative regulatory cells did not significantly affect EAE development. The (re-)activation of lymphocytes in sick Devic mice mainly occurs in the CNS without evidence of priming in the peripheral lymphoid organs. MOG-specific B and T cells cooperate by means of several mechanisms. MOGspecific B cells, which bind MOG but not the immunodominant peptide MOG 35-55 via their surface immunoglobulin (Ig), efficiently presented even high dilutions of MOG to T cells. This resulted in the enhanced proliferation of T and B cells as well as rapid activation. Stimulated T, but not B cells, secreted large amounts of Th1 cytokines IFNg and IL-2 along with small amounts of Th2 cytokine IL-5. In addition, MOG-stimulated T and B cells expressed a set of co-stimulatory molecules, which further help to modulate the proliferation and activation. Surprisingly, the doubletransgenic Devic mice, but not their single transgenic littermates, had high titers of MOG-specific IgG1 antibodies in the serum, which indicates a previous encounter with antigen in vivo. However, similar MOG-specific serum IgG1 titers were present irrespective of the clinical status. The transfer of EAE by Devic splenocytes in immunodeficient mice or by bone marrow reconstitution in wild-type mice further supported the in vivo cooperation of MOG-specific T and B cells to induce spontaneous EAE. In summary, Devic mice show several salient features that are important for study of the pathogenic mechanisms of CNS autoimmunity. As a model of spontaneous autoimmunity, they may allow us to study the triggering factors of autoimmunity as well as the factors that determine restricted infiltration of immune cells into the CNS.In addition, the model may be useful for validating novel therapies for autoimmune CNS diseases

Die Applikation von Probenecid in zwei Tiermodellen der Multiplen Sklerose: Positive Effekte auf Myelinisierung und Immunstatus

Multiple Sklerose stellt ein häufiges neurologisches Krankheitsbild dar, für das es bisher keine ursächliche Therapie gibt und dessen palliative und symptomatische Therapie oft mit einer Vielzahl an Nebenwirkungen einhergeht. Um die komplexe Pathophysiologie besser zu verstehen, werden seit Jahrzehnten verschiedene Mausmodelle der Multiplen Sklerose eingesetzt, aus deren Erforschung bereits neue Therapieoptionen hervorgegangen sind. In der vorliegenden Arbeit wurden das toxische Cuprizon-Modell und das immunologische EAE-Modell verwendet, um mögliche positive Wirkungen des Gichtmedikaments Probenecid zu untersuchen. Es sollte überprüft werden, ob Probenecid im Cuprizon-Modell eine Demyelinisierung des optischen Nervens verringert und ob eine Probenecid-Therapie im EAE-Modell den Krankheitsverlauf der Versuchstiere günstig beeinflusst. In beiden Modellen sollten Zellzahlveränderungen mit durchflusszytometrischen Messungen verschiedener Leukozyten-Populationen in Blut und Milz detektiert werden, um so mögliche Hinweise auf eine immunologische Wirkung von Probenecid zu erhalten. Es wurde jeweils eine Versuchsgruppe mit einer täglichen intraperitonealen Probenecid-Injektion behandelt. Im Cuprizon-Versuch wurden von den entnommenen optischen Nerven ultrastrukturelle Querschnittsaufnahmen erstellt, auf denen die Axon-Durchmesser und g-ratios bestimmt und mithilfe der Generalized Estimating Equation miteinander verglichen wurden. Hierbei zeigte sich ein signifikant größerer medianer Axon-Durchmesser der mit Cuprizon therapierten Versuchsgruppe im Vergleich zu den Gruppen ohne Probenecid-Therapie, was einen deutlichen Hinweis gibt, dass eine Probenecid-Therapie Demyelinisierungsvorgänge mindert. Die Ursache dieser Probenecid-Wirkung liegt möglicherweise in einer Reduktion von oxidativem Stress oder in einem IL-1β vermittelten immunologischen Mechanismus, der sich auch auf den Neuritenschaden, der als Folge der Demyelinisierung entsteht, auswirkt. Interessant ist an dieser Stelle auch, dass die Demyelinisierung im optischen Nerven generell geringer ausgeprägt war, als in anderen Hirnregionen. Nach Blut- und Milzentnahme wurden die abgezählten Leukozyten gefärbt und durchflusszytometrisch absolute und prozentuale Zellzahlen verschiedener Leukozyten-Populationen bestimmt. In diesen Messungen fiel im Cuprizon-Versuch besonders auf, dass der prozentuale Anteil der CD3+CD4+CD25+ Lymphozyten in der Standardfutter-Gruppe sowohl im Blut als auch in der Milz signifikant höher als in allen CPZ-Gruppen war, während in den anderen Zellpopulationen keine Unterschiede im Gruppenvergleich auftraten. Dass die Unterschiede fast ausschließlich in der Population der CD25+-Zellen gefunden wurden, kann die These aufkommen, dass diese Zellen im CPZ-Modell vermindert auftreten, ohne dass dies durch eine Probenecid- oder Solvent-Therapie beeinflusst wurde. Die EAE-Tiere wurden mit einer MOG-Emulsion immunisiert und anschließend täglich untersucht, um anhand eines Scores den Krankheitsverlauf zu beurteilen. Ab einem bestimmten Krankheitsstadium wurden die Tiere mit Probenecid therapiert. Hierbei konnte festgestellt werden, dass eine Probenecid-Therapie den Krankheitsverlauf günstig beeinflusst. Es wurde ein Aufhalten der Symptomprogredienz gezeigt, die dosisabhängig war, da erst eine Probenecid-Dosis von 250 mg pro kg Körpergewicht ausreichte, um eine positive therapeutische Wirkung nachzuweisen. Da Probenecid Pannexin-Kanäle und P2X7-Rezeptoren blockiert, kann davon ausgegangen werden, dass dieser Angriffspunkt ein Ausgangspunkt mehrerer Prozesse mit unterschiedlichen und weitreichenden Folgen darstellt, von dem ausgehend verschiedene Mechanismen der Oligodendrozyten- und Neuronen-Schädigung ablaufen. Wahrscheinlich scheint hier einerseits ein Mechanismus, der ebenfalls ausgehend von IL-1β über den Signalweg der Inflammasom-Aktivierung auf die Blut-Hirnschranke und auf unterstützende Zellen des angeborenen Immunsystems wirkt, andererseits aber auch direkt eine Wirkung auf T-Lymphozyten entfaltet. Gestützt wird dieser Gedanke dadurch, dass im 250 mg EAE-Versuch der prozentuale Anteil der CD3+CD4+ Zellen pro Milz die Anteile der Kontroll-Gruppe und der EAE/PBN überstieg. Man könnte also hier davon ausgehen, dass bei zwar gleichgebliebener Treg-Anzahl, die Anzahl der autoreaktiven CD4+ T-Helferzellen in der EAE- und EAE/solvent-Gruppe am Ort der Antigenpräsentation im peripheren lymphatischen Organ zugenommen hat, während dies durch ein Probenecid-Therapie unterblieb. Diese Arbeit gibt Anhaltspunkte dafür, dass Probenecid als Therapeutikum bei Multipler Sklerose durchaus Sinn macht, da eine Therapie im Mausmodell nicht zu vernachlässigende Vorteile erbracht hat. Zusätzlich spricht das geringe Nebenwirkungsprofil in Verbindung mit der langen Erfahrung im Umgang mit dem Medikament zumindest für eine unterstützende Therapie. Es müssen jedoch einzelne Teilaspekte in weiterer Forschung genauer geklärt werden, um die Pharmakodynamik des Medikaments in Bezug auf die Pathophysiologie der Multiplen Sklerose besser zu verstehen.Multiple sclerosis is a common neurological disorder for which there is no causal therapy and whose palliative and symptomatic therapy is often associated with a variety of side effects. In order to better understand the complex pathophysiology, various mouse models of multiple sclerosis have been used for decades, from which research new therapeutic options have already emerged. In the present work, the toxic cuprizone model and the immunological EAE model were used to investigate possible positive effects of the gout medication probenecid. It should be examined whether probenecid in the cuprizone model reduces demyelination of the optical nerve and if a probenecid therapy in the EAE model favorably affects the course of the disease of the test animals. In both models, cell number changes should be detected by flow cytometry measurements of different leukocyte populations in blood and spleen in order to obtain possible evidence of an immunological effect of probenecid. One experimental group was treated with a daily intraperitoneal injection of probenecid. In the cuprizone test, the ultrastructural cross-sections were obtained from the extracted optical nerves, on which the axon diameter and g-ratios were determined and compared with the Generalized Estimating Equation. A significantly larger median axon diameter of the cuprizone treated experimental group was compared with the groups without probenecid therapy, which clearly indicates that a probenecid therapy reduces demyelination. The cause of this probenecid effect may be a reduction in oxidative stress or in an IL-1β-mediated immunological mechanism affecting neurite damage resulting from demyelination. It is also interesting at this point that the demyelination in the optical nerves was generally less pronounced than in other brain regions. After blood sampling and spleen removal, the abolished leukocytes were stained and absolute and percentage cell numbers of different leukocyte populations were determined by flow cytometry. In these measurements, the percentage of CD3+CD4+CD25+ lymphocytes in the standard feed group was significantly higher in both the blood and spleen than in all CPZ groups, whereas in the other cell populations there was no difference in the group comparison. The fact that the differences were found almost exclusively in the population of the CD25+ cells can lead to the thesis that these cells are reduced in the cuprizone model without this being influenced by probenecid or solvent therapy. The EAE animals were immunized with an MOG emulsion and then examined daily to assess the course of the disease by means of a score. From a certain stage of the disease the animals were treated with probenecid. It was found that probenecid therapy had a favorable effect on the course of the disease. There was shown a dose-dependent positive therapeutic effect, a dose of 250 mg per kg of body weight was needed to demonstrate a positive therapeutic effect. Since Probenecid blocks pannexin channels and P2X7 receptors, it can be assumed that this attack point is a starting point of several processes with different and far-reaching consequences, starting with different mechanisms of oligodendrocyte and neuronal damage. It is probable that on the one hand, a mechanism which also acts as a starting-point for IL-1β via the signaling pathway of inflammasome activation on the blood-brain barrier and on supporting cells of the innate immune system also appears to have an immediate effect on T-lymphocytes. This idea is supported by the fact that in the 250 mg EAE experiment, the percentage of CD3+CD4+ cells per spleen exceeded the proportions of the control group and the EAE/PBN. Thus, the number of autoreactive CD4+ T helper cells in the EAE and EAE/solvent group at the site of antigen presentation in the peripheral lymphatic organ has increased while the Treg number remains the same, while this did not occur through a probenecid therapy. This work provides evidence that probenecid as a therapeutic agent in multiple sclerosis makes sense, since a therapy in the mouse model has not led to negligible advantages. In addition, the low side-effect profile in combination with the long experience with the drug speaks at least for a supporting therapy. However, individual partial aspects have to be clarified in further research in order to better understand the pharmacodynamics of the drug with regard to the pathophysiology of multiple sclerosis

Cannabinoids for the control of experimental multiple sclerosis

PhDThere have been numerous studies reporting that cannabinoids, both exogenous and endogenous, have a potential beneficial function during incidences of neurological damage. Using gene knockout mice and cannabinoid-selective agents, this study demonstrates the diverse actions of cannabinoids with a particular focus on experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. The results presented here report on the action of stimulators of cannabinoid receptors in the nervous system (CNS) on; immune function, as a mechanism of suppressing autoimmune attack of the central nervous system, as agents to suppress neurodegenerative events leading to disease progression and as agents that can control signs of disease that occur as the consequences of autoimmune neurodegeneration such as spasticity. Tetrahydrocannabinol the psychoactive component in cannabis and the CB1 cannabinoid receptor appears to be central to many of the therapeutic actions of cannabis but also to the side-effect potential of cannabinoid drugs. This study reports on methods to avoid psychoactive side-effects of conventional brain-penetrant CB1 receptor agonists whilst exploiting the therapeutic potential of the cannabinoid system in order to control spasticity. This was achieved by targeting mechanisms of endocannabinoid degradation, particularly using fatty acid amide hydrolase inhibitors. Furthermore, this study also reports the development of novel cannabinoid compounds that are excluded from the brain and inhibit spasticity and also demonstrates the mechanism of exclusion of CNS-excluded cannabinoid CB1 receptor agonists. This study provides further evidence for the efficacy of cannabinoid compounds during an ongoing CNS disease and also their efficacy for treating the consequences of CNS autoimmune disease, which hopefully, will give additional impetus for further clinical investigations of cannabinoid agents in not only multiple sclerosis but also other neurodegenerative diseases of the CNS

Revealing the mechanism behind IL-23 driven autoimmunity

The immune system is remarkably effective in protecting the host against pathogenic insults. Despite several layers of self-tolerance mechanisms, the immune system is potentially capable to mount immune responses against self-antigens causing autoimmune diseases such as multiple sclerosis (MS). MS is characterized by the infiltration of inflammatory leukocytes into the central nervous system (CNS) resulting in axonal injury and demylination. During autoimmune neuro- inflammation, helper T (TH) cells initiate tissue damage and neurological impairment. Initially, IFN- γ-producing TH1 cells together with IL-12 were thought to be the driving force behind the inflammation observed in MS. Surprisingly however, it was only later found that the deletion of IFN-γ and the TH1 inducing cytokine IL-12 led to exacerbated disease development in experimental autoimmune encephalomyelitis (EAE), which serves as the animal model for MS. Now, it is widely held that IL-17-secreting T cells (TH17) rather than TH1 cells are the main encephalitogenic population in autoimmune inflammation and IL-23 supports the expansion/survival of IL-17-secreting T helper cells. To this day, none of the known TH17 signature cytokines (IL-17A, IL-17F, IL-22, IL-21) has been shown to be mandatory for the development of EAE. Nevertheless, IL-23 as well as the TH17 transcription factor RORγt elicits an encephalitogenic program, which leads to the production of a so far unknown encephalitogenic factor or combination of factors and ultimately initiates the development of EAE. We demonstrated that IL-23-medaited effect on T cell pathogenicity is a feature far beyond T cell polarization. IL-23 not only promotes TH17 polarization but also and more critically influences T cell CNS-tropism. The lack of IL-23R engagement interferes with the capacity of T cells to produce pro-inflammatory cytokines (IL-17A, IFN-γ and GM-CSF) in vivo and to acquire pro- inflammatory properties. Furthermore, we showed that rather than „conventional“ TH17 cytokines, GM-CSF production marks the population of neuro-encephalitogenic T cells and its production is dependent on the activity of the IL-12/23 receptor complex and RORγt. Conversely, IFN-γ, IL-12 and IL-27 inhibit RORγt expression and the secretion of GM-CSF. Taken together, here we describe that IL-23 elicits an encephalitogenic program in neuro-Ag- reactive T cells which leads to their ability to invade the CNS and promotes the production of GM- CSF which, in contrast to IL-17 or IFN-γ, is the only known T cell-derived factor with a non redundant function in CNS autoimmune disease today. Das Immunsystem ist ausgesprochen effektiv darin, den Wirt gegen eindringende Pathogene zu schützen. Trotz verschiedener Mechanismen die zur Toleranzentwicklung beitragen, kann es unter Umständen zu einer Immunantwort gegen Selbst-Antigene kommen, was zu Autoimmunerkrankungen wie der Multiplen Sklerose (MS) führen kann. MS wird durch das Einwandern von entzündungsinduzierenden Leukozyten ins zentrale Nervensystem (ZNS) ausgelöst. Dies hat axonale Schäden und Demyelinisierung zur Folge. Während dieser autoimmunen, neuronalen Entzündungsreaktion, initiieren Helfer T (TH) Zellen die Gewebeschädigung und die damit verbundene neurologische Beeinträchtigung. Lange hat man geglaubt, dass in erster Linie IFN-γ-produzierende TH1 Zellen zusammen mit IL-12 für diese neuronale Entzündung in MS verantwortlich sind. Allerdings wurde später entdeckt, dass die Neutralisierung von IFN-γ sowie von dem TH1-induzierenden Cytokin, IL-12, zur Verschlimmerung des Krankheitsbildes in der experimentellen autoimmunen Encephalomyelitis (EAE), dem Tiermodell für MS, führt. Heutzutage wird weitgehend davon ausgegangen, dass IL-17A ausschüttende T Zellen (TH17) anstelle von TH1 Zellen die Hauptpopulation der encephalitogenen Zellen in der autoimmunen Entzündung darstellen. Diese TH17 Zellen und deren Expansion/Überleben werden durch das Cytokin IL-23, unterstützt. Bis heute, konnte jedoch keinem der TH17 spezifischen Cytokine (IL-17A, IL-17F, IL-22, IL-21) eine essentielle Rolle in der Entwicklung von EAE zugeschrieben werden. Nichtsdestotrotz führt IL-23 sowie der TH17- Transkriptionsfaktor RORgt zu einem encephalitogenen Programm, welches zur Produktion von einem oder einer Kombination von bisher unbekannten encephalitogenen Faktoren führt, welche schlussendlich die Entwicklung von EAE hervorrufen. Wir konnten zeigen, dass der IL-23-vermittelte Effekt auf die Pathogenizität von T Zellen eine Eigenschaft ist, die weit über die T Zell-Polarisierung hinaus geht. IL-23 begünstigt nicht nur die Polarisierung von TH17 Zellen, sondern beeinflusst ebenfalls die Migration dieser Zellen ins ZNS. Das Fehlen des IL-23R interferiert mit der Kapazität von T Zellen, pro-inflammatorische Cytokine (IL-17A, IFN-γ und GM-CSF) in vivo zu produzieren und somit pro-inflammatorische Eigenschaften zu erwerben. Weiter haben wir gezeigt, dass GM-CSF Produktion die neuro- encephalitogene T Zell Population besser kennzeichnet als die konventionellen TH17 Cytokine. Die Produktion von GM-CSF ist außerdem von der Aktivität des IL-12/23 Rezeptor-Komplexes sowie von dem Transkriptionsfaktor RORgt abhängig. Im Gegenzug hemmt IFN-γ, IL-12 und auch IL-27 die RORgt Exprimierung sowie die Ausschüttung von GM-CSF. Zusammengefasst konnten wir zeigen, dass IL-23 ein encephalitogenes Programm in neuroantigenreaktiven T Zellen hervorruft, welches diese befähigt, ins ZNS einzuwandern. Zusätzlich zeigen wir, dass IL-23 die Produktion von GM-CSF positiv beeinflusst, welches im Gegenteil zu IL-17 oder IFN-γ, der einzig bekannte von T Zellen stammende Faktor ist, der bis heute eine nicht-redundante Funktion in ZNS-Autoimmunerkrankungen hat

The role of mast cells in CD8+ T cell-mediated immune responses

A precisely regulated crosstalk between innate and adaptive immunity is a prerequisite for an optimal immune response and successful survival strategy. Important players of innate immunity are the mast cells (MCs). These are long-living cells at sites of host-environment interface and important effector players during allergic responses. Recently, MCs have been described as central regulatory cells not only in innate but also in adaptive immune responses. MCs interact with cells of the adaptive immune system and recruit CD8+ T cells upon different stimuli. The purpose of this study was to investigate the interaction between MCs and CD8+ T cells, identify the factors that modulate this interaction and examine its downstream effects. By using murine bone marrow-derived MCs, this study demonstrated that MCs promote the survival of naïve, primary CD8+ T cells in an antigen-independent and cell-cell contact-dependent manner. The investigation of the antigen-dependent interaction between MCs and CD8+ T cells showed that MCs induce antigen-specific activation, proliferation and cytokine secretion by TCR-transgenic CD8+ T cells in vitro. Furthermore, the increased intracellular content of granzyme B and enhanced CD8+ T cell degranulation indicated an increase in the cytotoxic potential of CD8+ T cells. This antigen-driven communication between MCs and CD8+ T cells required both direct cell-cell contact and the release of soluble factors by MCs. TLR-mediated activation of MCs augmented their capacity to activate CD8+ T cells, partially due to enhanced surface expression of MHC class I molecules. Remarkably, the adoptive transfer of antigen-pulsed MCs induced proliferation of antigen-specific CD8+ T cells in vivo, in wild-type as well as in 2-microglobulin-deficient mice, which lack functional MHC class I expression. Thus, MCs promote CD8+ T cell responses, inducing effector CD8+ T cells in vitro and in vivo. Furthermore, CD8+ T cells enhanced the expression of several genes in MCs, in an antigen-dependent as well as antigen-independent manner, as demonstrated by differential gene expression analysis of MCs. Many of these genes are implicated in the signal transduction pathway of interferons, suggesting that the MC-CD8+ T cell interaction may contribute significantly to host defense mechanisms. Additionally, upregulation of major histocompatibility complex-related molecules and of the co-stimulatory molecule 4-1BB suggests that the contact with CD8+ T cells enhances the potential of MCs to modulate adaptive immune responses. In conclusion, this study adds new insights into the physiological role of MCs in the context of adaptive immune responses, such as a CD8+ T cell-driven antiviral immune response. This novel understanding of MC biology foresees new promising approaches for a therapeutic manipulation of antiviral immunity.Ein exakt regulierter Dialog zwischen angeborener und adaptiver Immunität ist eine wesentliche Voraussetzung für eine optimale Immunantwort und somit für eine erfolgreiche Überlebensstrategie. Zu den bedeutenden Zellen der angeborenen Immunität zählen unter anderen die Mastzellen (MZ). MZ sind langlebige Zellen, welche überwiegend an Umwelt-exponierten Körperflächen lokalisiert sind und wichtige Effektorzellen während einer allergischen Reaktion darstellen. Kürzlich wurden MZ als zentrale, regulatorische Zellen sowohl der angeborenen, als auch innerhalb der adaptiven Immunantwort beschrieben. MZ interagieren mit Zellen des angeborenen Immunsystems und vermögen nach unterschiedlicher Stimulation CD8+ T-Zellen zu rekrutieren. Absicht der vorliegenden Studie war es, die Interaktion zwischen MZ und CD8+ T-Zellen zu untersuchen, die diese Interaktion modulierenden Faktoren zu identifizieren und deren weiterführende Auswirkungen zu bestimmen. Unter Verwendung aus murinem Knochenmark generierter MZ zeigte diese Studie, dass MZ das Überleben naiver Primär-CD8+ T-Zellen Antigen-unabhängig und Zell-Zell-Kontakt-abhängig unterstützen. Untersuchungen der Antigen-abhängigen Interaktionen zwischen MZ und CD8+ T-Zellen zeigten, dass MZ eine Antigen-spezifische Aktivierung, Proliferation und Zytokinproduktion TCR-transgener CD8+ T-Zellen in vitro induzieren. Desweiteren deuten ein erhöhter intrazellulärer Gehalt an Granzym B und ein Anstieg der CD8+ T-Zell-Degranulation auf ein gesteigertes zytotoxisches Potential der CD8+ T-Zellen hin. Diese Antigen-gesteuerte Kommunikation zwischen MZ und CD8+ T-Zellen benötigte sowohl Zell-Zell-Kontakt als auch die Freisetzung löslicher Faktoren durch Mastzellen. Eine Aktivierung der MZ durch die Toll-like-Rezeptoren erhöhte deren Fähigkeit CD8+ T-Zellen zu aktivieren, teilweise vermittelt durch eine gesteigerte Zelloberflächenexpression der MHC Klasse I Molküle. Bemerkenswerter Weise induzierte der direkte Transfer Antigen-stimulierter MZ die Proliferation Antigen-spezifischer CD8+ T-Zellen in vivo, sowohl in wildtypischen als auch in 2-Mikroglobulin-defizienten Mäusen, welchen eine funktionale MHC Klasse I Expression fehlt. Somit wurde deutlich, dass MZ die CD8+ T-Zelle-Antwort fördern und dabei Effektor-CD8+ T-Zellen in vitro und in vivo induzieren. Zudem waren CD8+ T-Zellen in der Lage die Expression verschiedener Gene in MZ Antigen-abhängig als auch Antigen-unabhängig deutlich zu verstärken, wie mittels differentieller Genexpressionsanalyse gezeigt werden konnte. Viele dieser Gene haben eine wichtige Funktion innerhalb der Signaltransduktionswege von Interferonen, was zu der Annahme führte, dass die MZ-CD8+ T-Zell-Interaktion wesentlich zu Abwehrmechanismen beitragen könnte. Zusätzlich lässt die Hochregulation des Major Histocompatibility Complex-verwandten Moleküls 4—1BB vermuten, dass der Kontakt mit CD8+ T-Zellen das Potential der MZ, die adaptive Immunantwort zu modulieren, erhöhen könnte. Zusammenfassend ist zu sagen, dass diese Studie neue Einsichten in die physiologische Rolle der MZ im Kontext der adaptiven, wie einer CD8+ T-Zelle-gesteuerten anti-viralen Immunantwort gibt. Dieses neue Verständnis der MZ-Biologie birgt vielversprechende Ansätze für eine Manipulation der anti-viralen Immunantwort im therapeutischen Sinne