This thesis contains several investigations into the contribution of complement proteins, especially C1q, in several human diseases. Additionally, human autoantibodies against C1q (anti-C1q) are... Show moreThis thesis contains several investigations into the contribution of complement proteins, especially C1q, in several human diseases. Additionally, human autoantibodies against C1q (anti-C1q) are studied, cloned and characterized in order to further the understanding of their role in autoimmune disease. Show less
Rheumatoid arthritis (RA) is an autoimmune disease affecting joints which is hallmarked by the presence of autoantibodies against citrrulianted protein (ACPA). This thesis describes the phenotypic... Show moreRheumatoid arthritis (RA) is an autoimmune disease affecting joints which is hallmarked by the presence of autoantibodies against citrrulianted protein (ACPA). This thesis describes the phenotypic and functional characteristics of ACPA-expressing autoreactive B cells which suggest potential pathologic roles of these B cells in RA pathogenesis. The thesis also describes strategies to specifically deplete ACPA-expressing B cells to improve current RA therapeutic options. Show less
Muscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disorder caused by predominantly IgG4 antibodies targeting the MuSK protein. IgG4 has the unique ability to... Show moreMuscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disorder caused by predominantly IgG4 antibodies targeting the MuSK protein. IgG4 has the unique ability to exchange half-molecules with other IgG4s, resulting in monovalent binding to their antigen. To investigate if MuSK-antibody valency influences its pathogenicity, recombinant bivalent and functionally monovalent MuSK antibodies were generated from B-cell receptor sequences isolated from MuSK MG patients. Passive transfer studies revealed that monovalency amplifies MuSK antibody pathogenicity in vivo. This may be because monovalent MuSK antibodies inhibit MuSK signaling (antagonist), while bivalent MuSK antibodies activate MuSK signaling (agonist) in vitro. The binding epitope on MuSK further influences the consequences and pathogenicity of MuSK antibodies. Collectively, these results suggest that the pathophysiology in individual patients depends on their unique antibody composition and that class-switching to IgG4 is a critical step in developing MuSK MG. Furthermore, the IgG4 response against MuSK does not appear to result from a global increase in IgG4 responses, as MuSK MG patients only had mildly elevated serum IgG4. Instead, it is thought to be driven by the antigen itself. Importantly, MUSK and other MG associated genes are also expressed outside skeletal muscle. These locations are at risk for non-motor symptoms caused by autoantibodies or mutations, or for side-effects of targeted therapeutic strategies. Show less
For patients with immune-mediated inflammatory diseases (IMIDs), concerns exist about increased disease ac-tivity after vaccination. We aimed to assess changes in disease activity after SARS-CoV-2... Show moreFor patients with immune-mediated inflammatory diseases (IMIDs), concerns exist about increased disease ac-tivity after vaccination. We aimed to assess changes in disease activity after SARS-CoV-2 vaccination in patients with IMIDs, and determine risk factors for increased disease activity. In this substudy of a prospective obser-vational cohort study (Target-to-B!), we included patients with IMIDs who received a SARS-CoV-2 vaccine. Patients reported changes in disease activity on a five-point Likert scale every 60 days for up to twelve months after first vaccination. In case of self-reported increased activity, hospital records were screened whether the treating physician reported increased activity, and for potential intensification of immunosuppressive (ISP) treatment. Mixed models were used to study determinants for self-reported increased disease activity. In total, 2111 patients were included for analysis after primary immunization (mean age 49.7 years [SD 13.7], 1329/ 2111 (63.0%) female), from which 1266 patients for analysis after first additional vaccination. Increased disease activity at 60 days after start of primary immunization was reported by 223/2111 (10.6%). In 96/223 (43.0%) the increase was confirmed by the treating physician and in 36/223 (16.1%) ISP treatment was intensified. Increased disease activity at seven to 60 days after additional vaccination, was reported by 139/1266 (11.0%). Vaccinations were not temporally associated with self-reported increased disease activity. Conversely, increased disease activity before first vaccination, neuromuscular disease, and multiple sclerosis were associated. Alto-gether, self-reported increased disease activity after vaccination against SARS-CoV-2 was recorded in a minority of patients and was generally mild. Moreover, multivariate analyses suggest that disease related factors, but not vaccinations are the major determinants for self-reported increased disease activity. Show less
For patients with immune-mediated inflammatory diseases (IMIDs), concerns exist about increased disease activity after vaccination. We aimed to assess changes in disease activity after SARS-CoV-2... Show moreFor patients with immune-mediated inflammatory diseases (IMIDs), concerns exist about increased disease activity after vaccination. We aimed to assess changes in disease activity after SARS-CoV-2 vaccination in patients with IMIDs, and determine risk factors for increased disease activity. In this substudy of a prospective observational cohort study (Target-to-B!), we included patients with IMIDs who received a SARS-CoV-2 vaccine. Patients reported changes in disease activity on a five-point Likert scale every 60 days for up to twelve months after first vaccination. In case of self-reported increased activity, hospital records were screened whether the treating physician reported increased activity, and for potential intensification of immunosuppressive (ISP) treatment. Mixed models were used to study determinants for self-reported increased disease activity. In total, 2111 patients were included for analysis after primary immunization (mean age 49.7 years [SD 13.7], 1329/2111 (63.0%) female), from which 1266 patients for analysis after first additional vaccination. Increased disease activity at 60 days after start of primary immunization was reported by 223/2111 (10.6%). In 96/223 (43.0%) the increase was confirmed by the treating physician and in 36/223 (16.1%) ISP treatment was intensified. Increased disease activity at seven to 60 days after additional vaccination, was reported by 139/1266 (11.0%). Vaccinations were not temporally associated with self-reported increased disease activity. Conversely, increased disease activity before first vaccination, neuromuscular disease, and multiple sclerosis were associated. Altogether, self-reported increased disease activity after vaccination against SARS-CoV-2 was recorded in a minority of patients and was generally mild. Moreover, multivariate analyses suggest that disease related factors, but not vaccinations are the major determinants for self-reported increased disease activity. Show less
Muscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disease belonging to a growing group of IgG4 autoimmune diseases (IgG4-AIDs), in which the majority of pathogenic... Show moreMuscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disease belonging to a growing group of IgG4 autoimmune diseases (IgG4-AIDs), in which the majority of pathogenic autoantibodies are of the IgG4 subclass. The more prevalent form of MG with acetylcholine receptor (AChR) antibodies is caused by IgG1-3 autoantibodies. A dominant role for IgG4 in autoimmune disease is intriguing due to its antiinflammatory characteristics. It is unclear why MuSK autoantibodies are predominantly IgG4. We hypothesized that MuSK MG patients have a general predisposition to generate IgG4 responses, therefore resulting in high levels of circulating IgG4. To investigate this, we quantified serum Ig isotypes and IgG subclasses using nephelometric and turbidimetric assays in MuSK MG and AChR MG patients not under influence of immunosuppressive treatment. Absolute serum IgG1 was increased in both MuSK and AChR MG patients compared to healthy donors. In addition, only MuSK MG patients on average had significantly increased and enriched serum IgG4. Although more MuSK MG patients had elevated serum IgG4, for most the IgG4 serum levels fell within the normal range. Correlation analyses suggest MuSK-specific antibodies do not solely explain the variation in IgG4 levels. In conclusion, although serum IgG4 levels are slightly increased, the levels do not support ubiquitous IgG4 responses in MuSK MG patients as the underlying cause of dominant IgG4 MuSK antibodies. Show less
In order to be able to develop effective medicine and treatments to prevent or cure autoimmune diseases or cancer we need to understand the mechanisms how they arise and what drives their course... Show moreIn order to be able to develop effective medicine and treatments to prevent or cure autoimmune diseases or cancer we need to understand the mechanisms how they arise and what drives their course.Unravelling the fundamental molecular mechanisms influencing the onset and course of diseases such as allergies, rheumatoid arthritis or cancer can be tackled using bioorthogonal antigens – chemically functionalized proteins.To tackle this challenge this thesis uses an inter-disciplinary approach. Combining standard immunological experimental methods with special, highly selective bioorthogonal chemical reactions. These reactions are bioorthogonal because, unlike normal organic chemistry, they are compatible with the physiological environment of a cell. This approach allows for following for example the location of the protein over time within a cell or alterations in the immune response due to disease related changes to the protein without disturbing the processes themself.This is a significant advantage because without changing the method used, new information can be retrieved from the same set of experiments, at any point in time during the process and a plethora of new readout options yielding additional data sets.This promises new insights into the causal relation of time, localisation and factors influencing effective anti-cancer vaccine-design and cancer immunotherapy or new biological drugs to prevent or delay onset and progression of autoimmune diseases. Show less
This thesis describes two studies on the efficacy and safety of vaccinations in patients stable autoimmune myasthenia gravis, one with tetanus revaccination and one with influenza vaccination. Of... Show moreThis thesis describes two studies on the efficacy and safety of vaccinations in patients stable autoimmune myasthenia gravis, one with tetanus revaccination and one with influenza vaccination. Of both vaccinations, the humoral response and clinical parameters of the disease are described. For tetanus revaccination, also the cellular response is described. Furthermore, the validation of a disease specific quality of life questionnaire is described. Show less
The distribution of muscle weakness in MG is highly heterogeneous and frequently shifts in patients. In 5% of patients MG was restricted to ocular weakness, whereas 7% of patients never had any... Show moreThe distribution of muscle weakness in MG is highly heterogeneous and frequently shifts in patients. In 5% of patients MG was restricted to ocular weakness, whereas 7% of patients never had any form of ocular weakness throughout their disease course. In 83% of MG patients at least one other extra-ocular muscle was involved at the second visit.Patients with late-onset MG and the presence of additional autoimmune diseases had more exacerbations (OR = 47) and emergency treatments (OR = 26) than early-onset MG patients without other autoimmune diseases.MG-ADL (patient questionnaire on ADL) was found to be relatively insensitive to changes in generalized weakness. This led to the absence of a significant treatment response on MG-ADL in the presence of a significant response on QMG (an objective measure of muscle weakness) in the eculizumab study. A new ADL outcome measure, MGII, was shown to have a higher sensitivity for generalized weakness than MG-ADL.RoVEMP, a novel neurophysiological test, was shown to be a specific measure for myasthenic extra-ocular muscle weakness. In addition, we found a significant correlation between magnitude of decrement and the time since the last intake of pyridostigmine, supporting that RoVEMP decrement reflects reversible neuromuscular transmission failure. 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
The term __chimerism__ originates from Greek mythology and refers to the creature Chimaera, whose body was in front a lion, the back a serpent and the midsection a goat. In medicine, the term... Show moreThe term __chimerism__ originates from Greek mythology and refers to the creature Chimaera, whose body was in front a lion, the back a serpent and the midsection a goat. In medicine, the term chimerism refers to an individual, organ or part consisting of tissues of diverse genetic constitution. Pregnancy, blood transfusion and organ transplantation are potential causes of chimerism. In this thesis the occurrence of chimerism is investigated in different organs of healthy women, of women with the autoimmune disease Systemic Lupus Erythematosus (SLE) and of women that received a renal allograft. To demonstrate chimerism, male cells were detected in female organs by using in situ hybridization of the Y chromosome. Chimerism was found in 18% of healthy organs, in about 50% of organs derived from women with SLE and in none of the skin tumors investigated from female renal allograft recipients. In various organ types and both in women with and without sons and women with and without a transfusion history, chimerism was present. In this thesis we describe these results and review data from the ancient and recent literature. With all these data in hand, we speculate about the sources of chimerism and its implications on immunity. Show less
