Our immune system is supposed to protect us from infections, but it can also attack our own tissues if not properly controlled. This can lead to autoimmune diseases like rheumatoid arthritis (RA).... Show moreOur immune system is supposed to protect us from infections, but it can also attack our own tissues if not properly controlled. This can lead to autoimmune diseases like rheumatoid arthritis (RA). People with RA have antibodies to the body’s own proteins (self), but it is not known how they arise. The data described in this thesis show that these antibodies cross-react with self-proteins carrying different post-translational modifications, suggesting that multiple proteins may be involved in the initial loss of the immune system’s ability to discriminate between self- and foreign-proteins. As another unique feature, these antibodies carry additional sugars at an unexpected site in the molecule. Our data show that these sugars (variable domain glycans) can prevent binding to potential self-proteins, affect complement activation, and set the threshold for immune B-cell activation. In addition, our data show that the abundance of these sugars increases toward disease onset and predicts the development of chronic, persistent disease or the chance of subsequent remission. Taken together, these sugars may help B cells to escape the tight control mechanism in our body that are in place to prevent the development autoimmunity. This new “sugar mechanism” could be beneficial for diagnosis and future treatment. Show less
In this thesis, the involvement of the complement system was studied in various diseases that affect the microvasculature of the kidney. We focused on the clinicopathologic significance of... Show moreIn this thesis, the involvement of the complement system was studied in various diseases that affect the microvasculature of the kidney. We focused on the clinicopathologic significance of complement deposits along the renal microvasculature of patients with thrombotic microangiopathy, a disorder that is characterized by severe endothelial injury and microvascular thrombosis; IgA nephropathy and IgA vasculitis with nephritis, auto-immune disorders that can cause microvascular injury in adults and children; transplant glomerulopathy, an important cause of late graft dysfunction and renal allograft loss; preeclampsia, a leading cause of maternal and perinatal morbidity and mortality; and diabetic nephropathy, a microvascular complication of diabetes mellitus and a leading cause of end-stage renal disease. Special attention was paid to C4d, a cleavage product of C4 activation, which is commonly used as a biomarker for complement activation. Our data suggest that the complement system is involved in the pathogenesis of various renal microangiopathies and that complement activation along the microvasculature may contribute to disease progression in a subset of patients. Our findings may contribute to the development of improved diagnostic workup, new therapeutic strategies and patient-tailored therapy. Show less
In this thesis we have analyzed an important number of laboratory, radiological, clinical and patient´s reported outcomes in systemic lupus erythematosus (SLE) patients presenting with... Show moreIn this thesis we have analyzed an important number of laboratory, radiological, clinical and patient´s reported outcomes in systemic lupus erythematosus (SLE) patients presenting with neuropsychiatric (NP) manifestations. Our studies are among the most robust to date in this field due to the large number of patients included, the prospective character and the standard assessment followed by a multidisciplinary expert consensus.Furthermore our studies include the novelty of a phenotypic characterization of all NP manifestations according to the suspected underlying pathophysiological mechanism (inflammation or immune-mediated vs. ischemic or thrombotic). These studies give more light to the understanding of the underlying pathophysiological mechanisms of nervous involvement in SLE. Show less
In this thesis we investigated various mechanisms by which the immune system plays a role in the development of diabetic nephropathy. In chapter 2 we describe that APOC1-tg mice develop... Show moreIn this thesis we investigated various mechanisms by which the immune system plays a role in the development of diabetic nephropathy. In chapter 2 we describe that APOC1-tg mice develop glomerulosclerosis at 15 months of age, with increased number of glomerular macrophages. Our results suggest that apoCI may exacerbate the development of DN by increasing the inflammatory response in activated glomerular macrophages. In chapter 3 we demonstrate that sFLT-1 significantly improves kidney function, resolves diabetes-related kidney damage, and reduces endothelial cell activation and inflammation, suggesting that sFLT-1 can reduce the severity of DN by reducing glomerular inflammation and supporting cellular repair mechanisms.In chapter 4 we show that reducing endoglin levels diminished VEGF-A-induced endothelial activation by increasing pAkt and reducing pATF-2. These data suggest that targeting endoglin may have therapeutic value in patients who are at risk for developing DN.In chapter 5 we demonstrate that renal complement activation is associated with more severe classes of DN, reduced kidney function, and the presence of histological lesions.In chapter 6 we describe that transfecting APOC1-tg mice with sFlt-1 does not accelerate development of glomerulosclerosis, but lowered the number of glomerular macrophages. These data suggest that sFLT-1 treatment has an anti-inflammatory effect. Show less
The complement system is an important part of the innate immune system and can be divided in three different pathways; the classical, the lectin and the alternative pathway. In this thesis the... Show moreThe complement system is an important part of the innate immune system and can be divided in three different pathways; the classical, the lectin and the alternative pathway. In this thesis the role of C1q is investigated, which is the recognition molecule of the classical pathway. With the usage of epidemiological projects the clinical presentation of C1q deficient patients is investigated and the association of C1q in patients with Neuropsychiatric Systemic Lupus Erythematosus. Furthermore, using cellular based project the production and secretion of C1q by (non) immune cells is determined. Overall, this thesis is a nice overview about the importance of C1q in keeping the homeostasis and the role of C1q in disease. Show less
Rheumatoid arthritis is a chronic auto-immune disorder, of which persistent synovitis, bone erosions and auto-antibody formation are characteristic features. Although the etiology of the disease... Show moreRheumatoid arthritis is a chronic auto-immune disorder, of which persistent synovitis, bone erosions and auto-antibody formation are characteristic features. Although the etiology of the disease remains largely unknown, it is established that genetic risk factors play a pivotal role in disease pathology. Both family and twin studies have shown that the genetic contribution to the disease can be estimated around 50%. In the current thesis the genetic contribution of non-HLA genes to RA susceptibility was further investigated and the functional relevance of these loci was explored. The studies described were able to establish several previously identified risk factors in a statistical robust manner. Also novel genetic risk factors that are associated with RA susceptibility could be identified, as well as risk factors that are conferred to specific subgroups of the disease. Show less
Dendritic cells (DCs) are antigen-presenting cells (APCs) which play a key role in the regulation of immune responses. DCs are often referred to as __professional__ APCs, since their primary... Show moreDendritic cells (DCs) are antigen-presenting cells (APCs) which play a key role in the regulation of immune responses. DCs are often referred to as __professional__ APCs, since their primary function is to present antigens from pathogens or malignant cells. Consequently, there is a great deal of interest in how DCs might be exploited as a form of immunotherapy e.g. to induce immunity to cancers. However, DCs are also thought to play an important role in directing regulatory immune responses to innocuous antigens, which are targeted in autoimmune disease or during transplantation. Soluble factors secreted by DCs are crucial mediators in determining this balance between the immunogenic and regulatory arms of the immune system. One such group of factors is cytokines and one family which is gaining increasing attention is the IL-12 family. It is composed of four members; two are immunogenic and their expression has been very well characterised in DCs. The other two are regulatory, but relatively little is known about their regulation and expression in DC populations. In this thesis we aim to give a comprehensive overview of the expression and regulation of IL-12 family members in human DCs, with a particularly emphasis on IL-12, IL-27 and IL-35. Show less
The complement system has been shown to have a role in various systemic autoimmune (AI) diseases which have a renal component. This includes systemic lupus erythematosus (SLE), goodpastures... Show moreThe complement system has been shown to have a role in various systemic autoimmune (AI) diseases which have a renal component. This includes systemic lupus erythematosus (SLE), goodpastures syndrome and anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitides. In particular the classical pathway (CP) of complement is involved in SLE, with the exact mechanism of how these SLE autoantigens along with their autoantibodies interact with complement in the glomerulus remaining ambiguous. Furthermore, recent studies have demonstrated the expanding role of the alternative pathway (AP) of complement activation in steady state or in aspects of ANCA associated vasculitides or anti-GBM disease. The precise means of activation of the AP in these immune complex mediated disease settings remains unclear. Regulation is imperative in the AP due to its inherent ability to autoactivate. Factor H and properdin are both key opposing regulators in the AP with novel emerging roles in initiation and control of the AP. Deciphering the specific modes of AP activation and involvement is an ever expanding field requiring further elucidation, with previously unexpected roles for AP components revealing the diversity and complexity of this ancient pathway. Show less
The studies in this thesis describe the systematical search for factors involved in the pathophysiology of human renal I/R injury. Many of the processes assumed to be involved in renal I/R injury... Show moreThe studies in this thesis describe the systematical search for factors involved in the pathophysiology of human renal I/R injury. Many of the processes assumed to be involved in renal I/R injury based on animal studies could not be confirmed in our clinical study in humans. However, we found new evidence of complement activation and endothelial cell activation in human renal I/R injury. Moreover, there were large differences between deceased and living donor kidneys; brain dead donor kidneys have a unique proinflammatory cytokine release after reperfusion. Finally it appears that both brain dead and cardiac dead donor kidneys are not able to upregulate their metabolism-related genes upon reperfusion as living donor kidneys do, indicating that failure to restart metabolism may be a factor expanding I/R injury. All of these findings contribute to the understanding of renal I/R injury in humans and instigate the further search for therapeutical modalities to limit renal I/R injury. Show less
Preeclampsia is a pregnancy-specific condition that originates in the placenta. Despite decades of research, its pathogenesis remains largely unknown. However, several risk factors for preeclampsia... Show morePreeclampsia is a pregnancy-specific condition that originates in the placenta. Despite decades of research, its pathogenesis remains largely unknown. However, several risk factors for preeclampsia have been identified, including a (family) history of preeclampsia, autoimmune disease and conditions associated with endothelial damage, including hypertension, diabetes mellitus and preexistent renal disease. This thesis aims to further investigate through which mechanisms these risk factors increase the risk for preeclampsia. It deals with both the genetic background of preeclampsia, as well as the role of complement activation in its pathogenesis. Finally, it touches upon the role of angiogenic factors in the development of preeclampsia. Show less
B. burgdorferi has a wide variety of strategies to hide from the host immune system. Complement regulatory binding proteins have been described for almost all complement resistant B. burgdorferi sl... Show moreB. burgdorferi has a wide variety of strategies to hide from the host immune system. Complement regulatory binding proteins have been described for almost all complement resistant B. burgdorferi sl, except for the complement resistant B. bavariensis, one of the species that is known to frequently cause Lyme neuroborreliosis. In chapter 2 it is attempted to identify CRASP-1 proteins in B. bavariensis, formerly known as B. garinii OspA serotype 4. Potential CRASP-1 proteins will be cloned and studied for their ability to interact with host derived fluid phase regulators of complement. The specific role of complement resistance in early effective infection and dissemination of B. burgdorferi sl has not been well investigated. Can complement resistance lead to a better and more effective infection and dissemination? In chapter 3 an in vivo experiment in which the infectivity and dissemination patterns of complement sensitive and complement resistant B. burgdorferi sl in a C3 deficient mouse model is described. After effective transmission from the tick to the host the next challenge in B. burgdorferi infection is rapid and accurate detection of the pathogen. Diagnostics of Lyme disease is often compromised due to specific pathogen properties combined with technical shortcomings of bacterial serology. Two indirect detection methods which can aid in diagnosing patients suffering from Lyme neuroborreliosis were studied. In chapter 4 the performance of the C6-peptide ELISA for detecting antibodies in CSF in Lyme neuroborreliosis patients is studied. While in chapter 5 levels of CXCL13 in several patient populations as a potential biomarker for the diagnosis of Lyme neuroborreliosis is studied. For both indirect markers of presence of B. burgdorferi the specificity in clinically resembling and neuroinfectious diseases is of key importance. Several other infectious and inflammatory diseases that have a clinical presentation that can resemble Lyme disease are included in the analysis. Diagnosing Lyme disease can be difficult in some populations, first because Lyme disease is a relatively rare infection, resembling a large spectrum of other autoimmune and inflammatory diseases. Clinicians could often consider testing for Lyme disease. It is also important to do this in specific preselected populations, because the positive predictive value of a test, but specifically indirect tests such as serology, in a random population, is low.In chapter 6 all patients that present with complaints of arthritis at the early arthritis clinic are tested for Lyme arthritis. The prevalence of B. burgdorferi seropositivity in this population is studied. Another aim is to identify clinical factors which should urge the doctor to test, or explicitely not test, for Lyme disease in a patient presenting with arthritis in Europe. In chapter 7 a case of an HIV positive patient presenting with a meningoencephalitis caused by B. burgdorferi is described. The literature on HIV and Lyme neuroborreliosis co-infections is also reviewed. Show less
This thesis describes the clinical significance of thebiomarker C4d, a split product of the complement system, in several manifestations of systemic autoimmunediseases such as SLE and... Show moreThis thesis describes the clinical significance of thebiomarker C4d, a split product of the complement system, in several manifestations of systemic autoimmunediseases such as SLE and antiphospholipid syndrome. The findings in this thesis suggest that this biomarker might be of use in unraveling disease mechanisms where complement activation is involved, as well as serving as a diagnostic tool to detect patients at risk of antibody mediated tissue injury Show less
De activatie van zowel witte bloedcellen als complement systeem (betrokken bij het immuunsysteem) zijn geassocieerd met atherosclerose (slagaderverkalking). Het proefschrift bestaat uit drie delen;... Show moreDe activatie van zowel witte bloedcellen als complement systeem (betrokken bij het immuunsysteem) zijn geassocieerd met atherosclerose (slagaderverkalking). Het proefschrift bestaat uit drie delen; In deel I laten wij in 3 hoofdstukken zien dat vetten belangrijker zijn dan glucose voor de activatie van de witte bloedcellen en dus meer in staat zijn om een ontstekingsfenomeen op gang te brengen die leidt tot slagaderverkalking. Verder laten wij zien dat pati_nten met familiair verhoogd cholesterol (FH) en familiair verhoogd cholesterol en verhoogde voedingsvetten (triglyceriden) (FGH) na glucose-belasting een blijvende witte bloedcelactivatie hebben in tegenstelling tot gezonde vrijwilligers. Tenslotte werd aangetoond dat het structurele eiwit van de partikels waarin voedingsvetten vanuit de darmen worden vervoerd (apoB48) geassocieerd is met intima media dikte (een marker voor slagaderverkalking) In deel II associ_ren wij in 3 hoofstukken witte bloedcelactivatie met slagaderverkalking. Zo werd bijvoorbeeld aangetoond dat er in de kransslagaders met slagaderverkalking een hogere witte bloedcelactivatiestatus is dan in andere kransslagaders en bloedvaten zonder slagaderverkalking. Verder is de activatie van monocyten (een subgroep van witte bloedcellen) een voorspeller voor toekomstige hart- en vaatziekten. In deel III zijn ook 3 hoofdstukken beschreven met daarin de rol van mannose bindend lectine (MBL) die een van de routes is van complementactivatie (betrokken bij immuniteit; opruimen van lichaamsvreemde stoffen zoals bacteri_n). In hoofdstuk 1 werd beschreven dat mensen die lage MBL-waarden hebben, een minder effici_ntere vetstofwisseling hebben dan mensen met voldoende MBL-waarden. Echter, als we puur naar slagaderverkalking kijken, zien we dat MBL geen invloed heeft op de progressie van krasslagaderverkalking bij mensen met pre-existent krasslagaderverkalking. Show less
Major advancements in the understanding of the immune system have provided us with the opportunity for rational design of therapeutic immunological interventions. The notion that dendritic cells ... Show moreMajor advancements in the understanding of the immune system have provided us with the opportunity for rational design of therapeutic immunological interventions. The notion that dendritic cells (DC) play a crucial role in the activation of T lymphocytes has made DC biology of central importance for vaccine development. Accordingly, efficient delivery of antigen to DCs is one of main objectives in vaccine development. In this thesis, antibody-mediated antigen targeting is evaluated as a potential antigen delivery strategy for therapeutic vaccination. Complexes of protein antigen and antigen-specific antibodies are natural formulations that bind to Fc__ receptors. Fc__R ligation on DCs leads to efficient uptake, DC maturation and presentation of the antigen to T lymphocytes. Interaction of Ag-Ab complexes with Fc__Rs on DCs provides a link between the humoral and cellular arms of the immune response. This thesis contains an extensive evaluation of Fc__R-mediated antigen delivery to dendritic cells in the context of T lymphocyte-mediated immunotherapy. In addition, it contains a detailed analysis of Fc__R function on DCs and addresses the kinetics of cross-presentation of antigen after Fc__R-mediated uptake. Show less
The Guillain-Barr_ syndrome (GBS) is an acute, post-infectious neuropathy. Several clinical presentations are known, but general symptoms are symmetric muscle weakness and loss of tendon reflexes.... Show moreThe Guillain-Barr_ syndrome (GBS) is an acute, post-infectious neuropathy. Several clinical presentations are known, but general symptoms are symmetric muscle weakness and loss of tendon reflexes. In more than half of the GBS patients, antibodies against gangliosides can be detected in their serum. Gangliosides are glycosphingolipids, which are located in the outer layer of cell membranes, and play a role in cell-cell recognition and communication. Because gangliosides are highly enriched in the presynaptic nerve membranes, a role in synaptic transmission and the process of neurotransmitter release is assumed. We explored the physiological role of these gangliosides in transmitter release in neuromuscular synapses of mice using electrophysiological techniques. Furthermore, these synapses were also studied for the pathophysiological effects caused by antibodies against the gangliosides. The results show that gangliosides appear not to be fundamental for neuromuscular function, but rather have a modulating role. In addition, blocking of the complement system, using complement-component C5-inhibitors, is an effective method to protect the nerve membrane against the damaging effects of the activated complement system as a result of anti-ganglioside antibody binding. These and other experimental findings of this thesis are discussed in view of the current literature and the pathogenesis and therapeutical aspects of GBS. Show less
The innate immune system plays an important role in solid organ transplantation. This thesis focuses on the role of the lectin pathway of complement activation in kidney and simultaneous pancreas... Show moreThe innate immune system plays an important role in solid organ transplantation. This thesis focuses on the role of the lectin pathway of complement activation in kidney and simultaneous pancreas-kidney transplantation (SPKT) and describes the role of properdin in tubular complement activation and clearance of apoptotic cells. Mannose-binding lectin (MBL) is the initiating molecule of the lectin pathway of complement activation and its levels are largely determined by frequently occurring polymorphisms of the MBL gene. Our studies show that high MBL levels in the transplant recipient are associated with poorer graft survival and in the case of SPKT also with poorer survival of the recipient. While low MBL levels are associated with better survival we also show that low MBL does increase the risk for infectious complications after SPKT. Properdin is classically described as a stabilizer of the alternative pathway of complement activation. This thesis points towards a new role for properdin by describing a direct interaction with apoptotic cells and with the tubular epithelium of the kidney. By directly binding to these cellular surfaces properdin may contribute to the clearance of apoptotic cells and participate in complement activation and renal damage in proteinuric states. Show less
Activation of the complement system provides an important mechanism of defense of an organism against invading pathogens. In the healthy individual this defense is finely regulated to prevent... Show moreActivation of the complement system provides an important mechanism of defense of an organism against invading pathogens. In the healthy individual this defense is finely regulated to prevent attack of the complement system against cells and tissues of the host, however in abnormal situations this regulation can be out of balance. In the present thesis we look at a mouse model where the classical pathway of complement, in conjunction with anti-C1q autoantibodies, is shown to be involved in the development of renal disease (Chapter 2). In Chapter 3, a novel mouse model of complement-mediated glomerulonephritis is described. This model seems to be dependent on the alternative pathway of complement activation as well as on Fc receptors, and provides a novel tool to dissect the contribution of different effector systems in renal inflammation.Then the natural complement-inhibitory properties of the defensin Human Neutrophil Peptide-1 and the extracellular matrix molecules decorin and biglycan are investigated, which are presented to play a role in the regulation of complement in vitro, which hopefully can be extended to in vivo situations of health and disease in the near future (Chapter 4 & 5). The thesis is concluded with a general discussion in Chapter 6. Show less
The aim of this thesis was to gain more insight in the involvement of inflammatory processes in vessel wall remodeling seen after PTA or bypass surgery and put these processes in the perspective of... Show moreThe aim of this thesis was to gain more insight in the involvement of inflammatory processes in vessel wall remodeling seen after PTA or bypass surgery and put these processes in the perspective of restenosis, vein graft failure and potential therapeutic preventive strategies. Therefore, we firstly focused on inflammation in general, using the anti-inflammatory agent Dexamethasone, assessing the effects of such a broad approach on restenosis and vein graft remodeling. Then, we further focused on some specific parts of the immune system, namely Interleukin 10 (IL10), chemokines and the complement cascade. Il10 was chosen because it is one of the most studied anti-inflammatory cytokines and this property makes it a potential candidate for ant-restenosis therapy. Furthermore, it was hypothesized that chemokines are involved in vascular remodeling, since they are generally known for their regulatory properties regarding influx of inflammatory cells to tissues and this is one of the first phenomena seen in vascular remodeling. The complement cascade was studied in this context since it contains pro-inflammatory activity and some end-products of the cascade, like chemokines, are potent chemotactic agents. Show less
The major targets in Systemic lupus erythematosus (SLE, a systemic autoimmune disease) are nuclear components (DNA, histones, ribonucleoproteins), which are mainly derived from dying cells ... Show moreThe major targets in Systemic lupus erythematosus (SLE, a systemic autoimmune disease) are nuclear components (DNA, histones, ribonucleoproteins), which are mainly derived from dying cells (apoptotic and necrotic cells). Defective clearance of dying cells by phagocytes may lead to the breakdown of peripheral tolerance and initiation of autoimmune SLE. I have investigated the role of the innate immune system in the processing of dying cells and its immunological consequences. I found that a subset of macrophages driven by M-CSF have intrinsic anti-inflammatory properties and are potent phagocytes that have the unique capacity to preferentially bind and ingest early apoptotic cells in a silent manner. I also identified that human peritoneal macrophages freshly isolated from patients on peritoneal dialysis resemble functionally the in vitro-generated M-CSF-driven macrophages. I further showed that the anti-inflammatory and pro-inflammatory macrophages co-exist but can re-differentiate towards opposing phenotype depending on the local cytokine environment. Next to the phagocyte system, I investigated the role of components of the innate immune system in the processing of dying cells. I found that one of the complement regulators called properdin, binds predominantly to late apoptotic and necrotic cells independently of C3b, resulting alternative pathway complement activation. Show less
