A proper immune system is essential to fight off pathogens such as viruses, bacteria, and fungi. The immune system also plays a huge role in the protection against cancer, as it can eradicate tumor... Show moreA proper immune system is essential to fight off pathogens such as viruses, bacteria, and fungi. The immune system also plays a huge role in the protection against cancer, as it can eradicate tumor cells. All immune cells are derived from hematopoietic stem cells (HSC) that undergo differentiation in a highly regulated succession of developmental steps. Each of the cell types from the immune system perform a unique specialized role, and where most of these lineages develop in the bone marrow, the T cells that make part of our adaptive immunity, develop in the thymus within a specialized environment. To achieve this, the development of each of these cell types is regulated by a variety of transcription factors.In Chapter 2 of this thesis, we reviewed the complexity of one of the important signaling pathways of hematopoietic development, the Wnt pathway. While this serves as an introduction to the fundamental research we performed, it also shines light onto potential therapeutic targets within the Wnt pathway. For further study of the Wnt pathway, we generated a novel reporter mouse, which is described in Chapter 3 of this thesis. Here we developed a reporter mouse for the Axin2 gene with the fluorescent tag mTurquoise2 with CRISPR/Cas9 genome editing tools. Based on how the genetic engineering was done to create this reporter mouse, mice that are homozygous for this reporter knock-in are also a functional knockout for Axin2. For proper functional studies, the heterozygous mice should be used.The Axin2-mTurquoise2 mouse was used in Chapter 4 of this thesis to study Wnt involvement in hematopoiesis and T cell development. We observed an increase of canonical Wnt-signaling in thymocytes from mice that have a loss of Axin2 (Axin2-TQtg/tg mice). This confirms the Wnt dosage effect that was reported previously in literature. Conclusively, these results indicate that Axin2 is required to fine-tune Wnt activity to the levels that are “just right” and cannot be maintained by Wnt activator Axin1 alone.Chapters 2, 3 and 4 focused on fundamental research on hematopoiesis and T cell development. Chapter 5 is more translational oriented and is an introductory review to thymic regenerative therapies. In Chapter 6 of this thesis, we describe the development of a combined cell and gene therapy effort to regenerate a functional thymus transplant from human Induced Pluripotent Stem Cells (iPSCs). We generated an iPSC-derived thymus by directed differentiation of human iPSCs towards thymic epithelial progenitor cells (TEPCs) using FOXN1, formation of 3-D structures from these cells which we named iPSC-derived TEPCs, or iTEPCs, and transplantation of these organoids into mice that lack a functional thymus. Functionality was demonstrated by reconstitution of functional T cells from iPSC-derived grafts, which was introduced by FOXN1 gene therapy (FOXN1 iTEPCs).Chapter 7 is the final translational research chapter of this thesis and investigated the use of iPSCs for the modeling of PIDs and the initial steps towards T cell regeneration in SCID patients. This chapter describes the iPSC generation, and its repair to use gene-corrected iPSCs from a RAG2 SCID patient to repair their disrupted immune system. The resulting iPSC model was used for disease modelling and provided novel insights into the T cell development in these RAG2-SCID patients, as we observed developmental blocks at every investigated stage of T cell development. The findings in this chapter also provide a proof-of-principle to treat a variety of SCID patients by utilizing ex vivo cell and gene therapy.Altogether, this thesis tackles two sides of the same coin: fundamentals of hematopoiesis and T cell development, and regenerative therapies for the immune system. The fundamental tools and findings in this thesis can lead to important insights to find new treatment options or improve existing therapies. Furthermore, we provide the basis for two potential therapies to treat patients with a variety of immune disorders, including DiGeorge Syndrome, SCID, age-related immune deficiencies and (post-transplant) leukemia patients that received ablative therapies. Show less
Immune checkpoint therapies that aim to (re)activate the immune response against cancer cells have shown promising results in a variety of tumor types. Yet, a large fraction of cancer patients does... Show moreImmune checkpoint therapies that aim to (re)activate the immune response against cancer cells have shown promising results in a variety of tumor types. Yet, a large fraction of cancer patients does not benefit from these therapies. While the presence of a substantial number of immune cells, and in particular T cells, in the tumor is generally related with a better clinical response to checkpoint therapies, the T cells in the tumor are diverse in their capacity to eliminate the tumor. In order to improve treatment outcome of cancer patients, we require a better understanding of the roles of different T cells in the response (and resistance) to immune checkpoint therapy. The development of single cell profiling technologies has provided us with a powerful tool to analyze the state and functionality of individual cells. In this thesis, I have used single cell profiling methods in combination with innovative experimental technologies to unravel the diversity of T cells in human tumors and define the changes in the profiles of T cells that occur in response to treatment with immune checkpoint therapy to dissect which T cells are important for therapy response. Show less
This thesis describes the research that was performed to unravel the function and development of human lymphoid tissue-resident (lt)NK cells in relation to the circulating CD56bright and CD56dim NK... Show moreThis thesis describes the research that was performed to unravel the function and development of human lymphoid tissue-resident (lt)NK cells in relation to the circulating CD56bright and CD56dim NK cells. Two methods, RNA sequencing and flow cytometry, both commonly used in the field of immunology, were employed at the bulk and single-cell level. We highlighted the complexity of single-cell analysis that could potentially lead to misinterpretation, but also the additional value over bulk approaches by uncovering the cellular heterogeneity and developmental trajectories. Finally, our workflow for single-cell analysis was applied on a patient more than 50 years after hematopoietic stem cell transplantation to perform combined analysis of the T cell phenotype and T cell receptor repertoire. Show less
For many years, hematopoietic stem cell kinetics and/or cell signaling pathway activity has been studied through fluorescent in vitro or in vivo models. However, inaccurate measurement of the... Show moreFor many years, hematopoietic stem cell kinetics and/or cell signaling pathway activity has been studied through fluorescent in vitro or in vivo models. However, inaccurate measurement of the fluorescent proteins or lack of knowlegde about the genetic design of these models lead to incomplete conclusions. In the present thesis, in vivo fluorescent models are improved and new models are proposed together with analysis protocols to ensure precise measurement of fluorescent protein dynamics. Show less
The mechanisms involved in the autoimmune hypothesis of narcolepsy are investigated in this thesis. The role of HLA, auto- and cross-reactive T cells is explored and immune cell populations of... Show moreThe mechanisms involved in the autoimmune hypothesis of narcolepsy are investigated in this thesis. The role of HLA, auto- and cross-reactive T cells is explored and immune cell populations of interest are identified by a new technique, called mass cytometry. The second part of the thesis assesses unexplored clinical features of narcolepsy, such as weight gain and sleep state misperception. Show less
This thesis contains a variety of information about the natural and vaccine induced immunity against the human papillomavirus. The spontaneously induced HPV-specific humoral response after... Show moreThis thesis contains a variety of information about the natural and vaccine induced immunity against the human papillomavirus. The spontaneously induced HPV-specific humoral response after infection was assessed in population-based studies. The vaccine-induced changes in HPV-seroprevalence among the HPV unvaccinated Dutch population aged 0-89 years, where we compared the HPV-seroprevalence before the introduction of the HPV vaccine with data of approximately six years post-implementation of the national HPV vaccination program. Also, the HPV immune status of the Dutch Caribbean population just after introduction of HPV vaccination was determined. Moreover, the longitudinal relation between the hr-HPV antibody levels and the prevalence of HPV infections in three-dose vaccinated girls were studied. And more insight was gained into humoral and cellular immune responses after just a one-dose of the HPV vaccine. At last, the kinetics of innate and adaptive immune responses directly after vaccination different HPV vaccines were investigated. In the coming years some important changes are expected regarding HPV screening and vaccination. The effectiveness of the one-dose schedule will become clear as clinical trials end. In the Netherlands, a sex-neutral vaccination will be implemented soon. These changes will need to be monitored to provide scientific answers about the effectiveness and immunogenicity. Show less
In this thesis I have firstly applied gene transfer technologies to the redirection of T cell specificity, by trying to overcome limitations related to non-viral gene transfer systems. In the... Show moreIn this thesis I have firstly applied gene transfer technologies to the redirection of T cell specificity, by trying to overcome limitations related to non-viral gene transfer systems. In the second part of my PhD work, I focused on genetic screens, which, I applied to understanding molecular mechanisms of escape from T cell attack and to reveal mechanisms of PD-L1 regulation. The work presented in this thesis may on the one hand facilitate the clinical application of non-viral-based gene transfer systems in T cells. On the other hand, the more fundamental discoveries related to IFN-γ-mediated tumor cell killing and PD-L1 regulation may help to further understand resistance toward immunotherapies and how to overcome them. Show less
Atherosclerosis is the main underlying pathology of cardiovascular disease. Atherosclerosis is caused by an immune response which is directed against (modified) lipoproteins which accumulate in the... Show moreAtherosclerosis is the main underlying pathology of cardiovascular disease. Atherosclerosis is caused by an immune response which is directed against (modified) lipoproteins which accumulate in the vessel wall. Over time, this accumulation of lipids and immune cells induce morphological abnormalities in the vessel wall which cause the vessel lumen to narrow. This narrowing of the lumen (stenosis) causes ischemia in the downstream tissue. Prolonged ischemia causes myocardial ischemia and/or stroke. The research described in my thesis examines a well-recognized risk factor of atherosclerosis, being dyslipidemia, from an entirely new perspective. More specifically, it describes how dyslipidemia affects intrinsic metabolic processes in T cells, the conductors of the immune response characterizing atherosclerosis, and how this affects their function. My research has contributed to knowledge on the pathophysiology of atherosclerosis and might one day pave the way for the development of novel therapeutic approaches to treat cardiovascular disease. Show less
The breakthrough of immunotherapy for cancer has introduced promising new options, but nonetheless only a minority of cancer patients show significant clinical benefit. This situation has inspired... Show moreThe breakthrough of immunotherapy for cancer has introduced promising new options, but nonetheless only a minority of cancer patients show significant clinical benefit. This situation has inspired two avenues of research to find solutions to this problem: mechanistic studies to decipher the working mechanisms of immunotherapies and to investigate why many patients do not respond, and studies developing combination treatments to achieve clinical benefit in situations where immunotherapy alone is not sufficient. This thesis explores both these avenues by investigating applications of visible light in immunotherapy of cancer in pre-clinical models. We developed optical imaging platforms for visualization of immune cells and immunotherapies, which can shed light on the immunological events after administration of immunotherapy. In addition, we investigated novel therapies based on the combination of tumor ablation by Photodynamic Therapy and different types of immunotherapy. Our findings may prove useful in understanding success and failure of immunotherapy, and provide new combination treatment options when the efficacy of monotherapy is insufficient. Show less
Parasitic helminths are important organisms to study because their infections have both adverse and beneficial effects on the human host. Helminth infections are considered a burden, as these... Show moreParasitic helminths are important organisms to study because their infections have both adverse and beneficial effects on the human host. Helminth infections are considered a burden, as these infections cause significant morbidity in a large proportion worldwide. However, helminth infections, by means of their ability to modify host immune responses can also provide protection against inflammatory diseases (inflammatory bowel disease, diabetes, and asthma). It is important to better understand the underlying mechanisms of these Yin (positive) and Yang (negative) consequences of helminth infections. The general objective of this thesis is to track helminths at different levels. On the one hand to improve the detection of helminth infections, essential for the studying helminths and the interaction with their human host. Moreover, a more sensitive diagnostics is instrumental for monitoring the distribution of helminth infections and to evaluate the helminth infections elimination program. On the other hand, to understand the mechanistic insights of the interplay between helminths and the host immune system results in priming of Th2 and regulatory T cell responses. This could contribute to the identification of targeted pathways to manipulate immune responses, as part of developing therapeutics to treat inflammatory disorders characterized by deregulated Th2 and/or Treg responses. Show less
The objective of this PhD thesis is to understand mast cell (and basophil) functions and their role in autoimmune disease by focusing on three main aims: 1. To characterize the interaction between... Show moreThe objective of this PhD thesis is to understand mast cell (and basophil) functions and their role in autoimmune disease by focusing on three main aims: 1. To characterize the interaction between innate and Fc receptor triggers on mast cell and basophil function 2. To analyze the interaction between mast cells and CD4+ T cells 3. To understand the function of mast cells in chronic inflammation In this thesis I showed that mast cells can significantly contribute to chronic inflammation through their activation by Fc receptors and TLRs, as well as their interaction with CD4+ T cells, thereby increasing our understanding of their role in allergy and autoimmunity and providing several therapeutic targets to prevent mast cell-mediated immune responses. Show less
Seasonal influenza epidemics lead to severe flu in 3 to 5 million individuals and emerging pandemic influenza strains pose an even greater threat to society. We describe a clinical trial in which... Show moreSeasonal influenza epidemics lead to severe flu in 3 to 5 million individuals and emerging pandemic influenza strains pose an even greater threat to society. We describe a clinical trial in which vaccine-specific responses were measured during two consecutive influenza seasons, including the season in which the 2009 pandemic virus emerged, and showed that these vaccines induced both humoral and cellular responses. However, these responses are unlikely to be protective against newly emerging strains, due to the variable nature of influenza virus. Therefore, the other chapters in this thesis describe concepts within peptide-based vaccination strategies, which is one method to induce responses to highly conserved sequences of influenza virus. We evaluated a concept based on long peptides directed to highly conserved B and T cell epitopes and showed that this vaccine was capable of inducing both humoral and cellular immune responses. Furthermore, the vaccine provided partial protection against infection in an animal model. We also described another successful strategy to enhance the immunogenicity of minimal peptides by modification of these peptides and proceeded with formulations to improve delivery of these minimal peptides. Altogether, the findings in this thesis may contribute to the development of the next generation influenza vaccines. Show less
Current seasonal influenza vaccines rely on the induction of antibodies to neutralize the virus. However, influenza viruses frequently undergo genetic mutations due to antigenic drift and shift,... Show moreCurrent seasonal influenza vaccines rely on the induction of antibodies to neutralize the virus. However, influenza viruses frequently undergo genetic mutations due to antigenic drift and shift, altering the surface proteins hemagglutinin and neuraminidase to which antibodies usually bind. This could render vaccine-induced antibody responses ineffective, resulting in an ineffective influenza vaccine. Influenza vaccines based on the induction of T cell responses might be cross-reactive, since they target conserved influenza epitopes that do not tend to mutate. However, the peptide antigens that are able to induce such T cell responses are often poorly immunogenic. In this thesis, several formulation strategies are described that could improve the immunogenicity of influenza T cell peptide antigens. Using combinations of delivery systems and immunostimulators, the peptide antigens were able to induce influenza-specific T cell responses in mice. Furthermore, a model was developed that could predict the in vitro adjuvanticity of liposomes according to the liposomal lipid composition. In addition, the recent advances in influenza vaccine development are discussed. Finally, an alternative delivery system, the Bioneedle, was evaluated for the delivery of several influenza vaccines. Show less
Atherosclerose wordt veroorzaakt door een combinatie van verhoogde cholesterolniveaus en een chronische ontstekingsreactie. Deze ontstekingsreactie is het gevolg van een verstoorde balans tussen... Show moreAtherosclerose wordt veroorzaakt door een combinatie van verhoogde cholesterolniveaus en een chronische ontstekingsreactie. Deze ontstekingsreactie is het gevolg van een verstoorde balans tussen slechte, agressieve en goede, beschermende ontstekingscellen. In dit proefschrift wordt onderzocht hoe deze verstoorde balans in atherosclerose hersteld kan worden. Het onderzoek richt zich hierbij enerzijds op het remmen van de slechte ontstekingscellen en anderzijds op het stimuleren van de goede ontstekingscellen. Dit kan bereikt worden door de werking van costimulatoire en coinhibitoire eiwitten te be_nvloeden. Deze eiwitten zijn aanwezig op het celoppervlak van heel veel verschillende ontstekingscellen en bepalen of een ontstekingscel agressief of beschermend is. Costimulatoire eiwitten zorgen voor de activatie van een ontstekingscel, terwijl coinhibitoire eiwitten ontstekingscellen remmen. Blokkade van de costimulatoire eiwitten OX40L en CD30L remt atherosclerose, terwijl blokkade van het coinhibitoire eiwit Tim-3 atherosclerose verergert. Stimulatie van het coinhibitoire eiwit TIGIT vermindert de functie van T cellen. Een andere manier om de balans tussen goede en slechte ontstekingscellen te herstellen is door het aantal goede ontstekingscellen, zoals regulatoire T cellen en myeloid derived suppressor cellen, te laten toenemen. Eliminatie van regulatoire T cellen tot meer atherosclerose, terwijl een enorme expansie van regulatoire T cellen en myeloid derived suppressor cellen beschermend is. Show less
The homing of both immune cells and their malignant counterparts is, amongst others, determined by the interaction between locally produced chemokines and their corresponding receptors. In this... Show moreThe homing of both immune cells and their malignant counterparts is, amongst others, determined by the interaction between locally produced chemokines and their corresponding receptors. In this thesis we have addressed the involvement of distinct chemokine/chemokine receptor combinations in directing this cellular trafficking to specific organs. First, their role in the migration of leukaemic cells to extramedullary sites was investigated. Additionally, chemokine-guided T cell migration was studied in a patient with an inherited immunodeficiency (Omenn Syndrome), characterised by generalised erythrodermia of the skin. Allogeneic haematopoietic stem cell transplantation (HSCT) is the treatment of choice for both Leukaemia and Omenn Syndrome. A major drawback of this treatment is the occurrence of Graft-versus-Host Disease (GvHD). This complication results from migration of activated donor T cells to skin, liver and gut, where these cells induce inflammation and life threatening tissue destruction. We have investigated which chemokine/chemokine receptor interactions facilitate this migration to GvHD-affected skin in acute GvHD and also looked into the involvement of mHag-specific T cells in the onset of acute GvHD after gender mismatched HSCT. Finally, we studied chemokine receptor expression by T cells in chronic GvHD patients (a long-term complication of allogeneic HSCT) with fasciits as main clinical feature. Show less
Het transplanteren van stamcellen van een gezonde donor, allogene stamceltransplantatie, is een potentieel genezende behandeling van hematologische maligniteiten en aangeboren hematopo_etische... Show moreHet transplanteren van stamcellen van een gezonde donor, allogene stamceltransplantatie, is een potentieel genezende behandeling van hematologische maligniteiten en aangeboren hematopo_etische ziekten. In de periode na allogene stamceltransplantatie kunnen ernstige virale infecties optreden. Omdat het herstel van virus-specifieke T cellen gepaard gaat met bescherming tegen virale ziekte na stamceltransplantatie, is het overbrengen van virus-specifieke donor T cellen naar de ontvanger een aantrekkelijke strategie ter voorkoming of ter behandeling van virale ziekten. In dit proefschrift zijn methoden onderzocht om virus-specifieke CD8+ en CD4+ T cellen in perifeer bloed te activeren om detectie en isolatie van deze specifieke cellen mogelijk te maken. De resultaten beschreven in dit proefschrift onderbouwen de rationale voor het toepassen van cellulaire immuuntherapie voor virale infecties na stamceltransplantatie. Daarnaast zijn effici_nte en klinisch toepasbare methoden ontwikkeld om gecombineerde CD8+ en CD4+ T cel lijnen te produceren met hoge specificiteit voor meerdere peptiden van verschillende virale eiwitten. Deze methoden zijn breed toepasbaar en maken het mogelijk om de klinische waarde van cellulaire immuuntherapie voor behandeling van virale infecties na allogene stamceltransplantatie in klinische studies vast te stellen. Show less
Multiple Sclerosis is a degenerative disease of the central nervous system (CNS), involving autoimmunity against myelin, resulting in demyelination and paralysis. Antigen-specific immunotherapy may... Show moreMultiple Sclerosis is a degenerative disease of the central nervous system (CNS), involving autoimmunity against myelin, resulting in demyelination and paralysis. Antigen-specific immunotherapy may reduce this pathological autoimmunity, without disturbing normal immune function. This could be achieved by targeting of myelin antigens towards C-type lectin receptors (CLR) that recognize carbohydrate structures and are expressed on immune cells, because targeting of CLR under steady state conditions can suppress immunity in an antigen-specific way. In vitro studies showed that mannosylation of peptides results in internalization via the mannose receptor. In this study we observed, that immunization with mannosylated peptide does not induce disease in EAE, a model for Multiple Sclerosis. Instead, antigen-specific tolerance was induced; CNS inflammation was absent and DTH responses were impaired. Using transfer of TCR transgenic T cells in vivo we visualized that immunization with mannosylated peptide enhanced antigen presentation and induced vigorous expansion of T cells. However, T cells showed reduced blast formation and did not transfer EAE, despite normal production of inflammatory cytokines and chemokines. Lymphocytes accumulated in the lymph node of tolerized mice, which was counteracted by injection of Pertussis Toxin. Established EAE or ongoing DTH responses were ameliorated after mannosylated peptide treatment. In conclusion, mannosylated myelin peptide induced tolerance to EAE due to incomplete differentiation of encephalitogenic T cells and can be used to treat ongoing autoimmunity. Therefore, mannosylated antigens may represent a novel therapeutic approach for antigen-specific modulation of autoreactive T cells in vivo. Show less
This thesis introduces a novel T cell vaccination method that uses a tattoo machine to inject DNA in the skin of the vaccinee. In comparison to other experimental vaccination methods DNA tattooing... Show moreThis thesis introduces a novel T cell vaccination method that uses a tattoo machine to inject DNA in the skin of the vaccinee. In comparison to other experimental vaccination methods DNA tattooing is very strong: besides small laboratory animals also large animals mount strong T cell responses upon tattoo DNA vaccination. Show less
