Oratie uitgesproken door Prof.Dr. Leendert A. Trouw bij de aanvaarding van het ambt van hoogleraar Immunologie aan de Universiteit Leiden op vrijdag 2 februari 2024
Beukel, M.D. van den; Wesemael, T.J. van; Hoogslag, A.T.W.; Borggreven, N.; Huizinga, T.W.J.; Helm-van Mil, A.H.M. van der; ... ; Trouw, L.A. 2023
Objective In rheumatoid arthritis (RA) around two-thirds of patients are autoantibody positive for rheumatoid factor, anti-citrullinated protein antibodies and/or anti-carbamylated protein... Show moreObjective In rheumatoid arthritis (RA) around two-thirds of patients are autoantibody positive for rheumatoid factor, anti-citrullinated protein antibodies and/or anti-carbamylated protein antibodies. The remaining seronegative subgroup of patients is clinically heterogeneous and thus far, biomarkers predicting the disease course are lacking. Therefore, we analysed the value of other autoantibodies in RA directed against malondialdehyde-acetaldehyde adducts (MAA) and advanced glycation end-products (AGE).Methods In sera of 648 patients with RA and 538 patients without RA from the Leiden Early Arthritis Clinic, anti-MAA and anti-AGE IgG antibody levels were measured using ELISA. Associations between genetic risk factors, acute phase reactants, radiological joint damage, remission and anti-PTM positivity were investigated using regression, correlation and survival analyses.Results Anti-AGE and anti-MAA were most prevalent in RA (44.6% and 46.1% respectively) but were also present in non-RA arthritis patients (32.9% and 30.3% respectively). Anti-AGE and anti-MAA antibodies were associated with HLA-DRB1*03 within seronegative RA (OR=1.98, p=0.003, and OR=2.37, p<0.001, respectively) and, for anti-AGE also in non-RA arthritis patients (OR=2.34, p<0.001). Presence of anti-MAA antibodies was associated significantly with markers of inflammation, erythrocyte sedimentation rate and C reactive protein, in all groups independent of anti-AGE. Interestingly, the presence of anti-AGE and anti-MAA antibodies was associated with radiological progression in patients with seronegative RA, but not evidently with sustained drug-free remission.Conclusions Anti-AGE and anti-MAA were present in around 45% of RA patients and 30% of non-RA arthritis patients, and although not specific for RA, their presence associated with HLA, inflammation and, for RA, with clinical outcomes especially in patients with seronegative RA. Show less
Beukel, M.D. van den; Stoelinga, A.E.C.; Meer, A.J. van der; Meulen, S. van der; Zhang, L.; Tushuizen, M.E.; ... ; Trouw, L.A. 2023
Background(Auto)immune mediated and cholestatic liver disease (AILD) includes autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Especially AIH... Show moreBackground(Auto)immune mediated and cholestatic liver disease (AILD) includes autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Especially AIH is characterized by the presence of autoantibodies and elevated serum immunoglobulins. In rheumatoid arthritis, autoantibodies against post-translational modifications (PTMs) such as citrullination (Cit) and carbamylation (CarP) are used as diagnostic and prognostic markers, respectively. We studied the presence of six anti-PTM antibodies in patients with the three AILDs and non-AILD. MethodsAntibodies against six PTMs (malondialdehyde-acetaldehyde adducts (MAA), advanced glycation end-products (AGE), CarP, acetylation (AL), Cit, and nitration (NT)) were tested in sera of patients with AILD (n = 106), non-AILD (n = 101) and compared with healthy controls (HC) (n = 100). Levels and positivity were correlated with clinical and biochemical features in a well-defined cohort of untreated AIH patients. ResultsAnti-PTM antibodies were more often detectable in sera from AILD patients compared with HCs (anti-MAA: 67.9% vs. 2.0%, anti-AGE: 36.8% vs. 4.0%, anti-CarP: 47.2% vs. 5.0% and anti-AL: 18.9% vs. 5.0%). In untreated AIH, time to complete biochemical response (CBR) was associated with anti-MAA, anti-AGE, anti-CarP and anti-AL antibodies. Significantly more patients with at least three anti-PTM antibodies attained CBR at 12 months of treatment (13 vs. 3 p = 0.01). ConclusionAnti-PTM antibodies are frequently present in AILD. The presence of anti-MAA, anti-AGE and anti-CarP antibodies correlates with the presence of AIH within this cohort. In AIH, harboring at least three anti-PTM antibody responses is positively associated with CBR. Determination of anti-PTM antibodies in liver disease may have diagnostic and prognostic value. Show less
Tuberculosis (TB) is a prevalent disease causing an estimated 1.6 million deaths and 10.6 million new cases annually. Discriminating TB disease from differential diagnoses can be complex,... Show moreTuberculosis (TB) is a prevalent disease causing an estimated 1.6 million deaths and 10.6 million new cases annually. Discriminating TB disease from differential diagnoses can be complex, particularly in the field. Increased levels of complement component C1q in serum have been identified as a specific and accessible biomarker for TB disease but the source of C1q in circulation has not been identified. Here, data and samples previously collected from human cohorts, a clinical trial and a non-human primate study were used to identify cells producing C1q in circulation. Cell subset frequencies were correlated with serum C1q levels and combined with single cell RNA sequencing and flow cytometry analyses. This identified monocytes as C1q producers in circulation, with a pronounced expression of C1q in classical and intermediate monocytes and variable expression in non-classical monocytes. Show less
Essen, M.F. van; Schlagwein, N.; Hoven, E.M.P. van den; Gijlswijk-Janssen, D.J. van; Lubbers, R.; Bos, R.M. van den; ... ; COMBAT Consortium 2023
Properdin, the only known positive regulator of the complement system, stabilizes the C3 convertase, thereby increasing its half-life. In contrast to most other complement factors, properdin is... Show moreProperdin, the only known positive regulator of the complement system, stabilizes the C3 convertase, thereby increasing its half-life. In contrast to most other complement factors, properdin is mainly produced extrahepatically by myeloid cells. Recent data suggest a role for properdin as a pattern recognition molecule. Here, we confirmed previous findings of properdin binding to different necrotic cells including Jurkat T cells. Binding can occur independent of C3, as demonstrated by HAP-1 C3 KO cells, excluding a role for endogenous C3. In view of the cellular source of properdin, interaction with myeloid cells was examined. Properdin bound to the surface of viable monocyte-derived pro- and anti-inflammatory macrophages, but not to DCs. Binding was demonstrated for purified properdin as well as fractionated P2, P3, and P4 properdin oligomers. Binding contributed to local complement activation as determined by C3 and C5b-9 deposition on the cell surfaces and seems a prerequisite for alternative pathway activation. Interaction of properdin with cell surfaces could be inhibited with the tick protein Salp20 and by different polysaccharides, depending on sulfation and chain length. These data identify properdin as a factor interacting with different cell surfaces, being either dead or alive, contributing to the local stimulation of complement activation. Show less
Moel, E.C. de; Trouw, L.A.; Terao, C.; Govind, N.; Tikly, M.; El-Gabalawy, H.; ... ; Woude, D. van der 2023
Background: Rheumatoid arthritis (RA) occurs across the globe in different ethnic populations. Most RA patients harbor anti-modified protein antibodies (AMPA); however, it is unclear whether... Show moreBackground: Rheumatoid arthritis (RA) occurs across the globe in different ethnic populations. Most RA patients harbor anti-modified protein antibodies (AMPA); however, it is unclear whether differences exist in autoantibody responses at different geographic locations and between different ethnic groups, which could provide new clues regarding factors underlying autoantibody development. We therefore investigated AMPA prevalence and association with HLA DRB1 alleles and smoking in four ethnically diverse populations on four different continents. Methods: Anti-carbamylated (anti-CarP), anti-malondialdehyde acetaldehyde (anti-MAA), and anti-acetylated protein antibodies (anti-AcVim) IgG were determined in anti-citrullinated protein antibody-positive Dutch (NL, n = 103), Japanese (JP, n = 174), First Nations Peoples in Canada (FN, n = 100), and black South African (SA, n = 67) RA patients. Ethnicity-matched local healthy controls were used to calculate cut-offs. Risk factors associated with AMPA seropositivity in each cohort were identified using logistic regression. Results: Median AMPA levels were higher in First Nations Peoples in Canada and especially South African patients, as reflected by percentage seropositivity: NL, JP, FN, and SA: anti-CarP: 47%, 43%, 58%, and 76% (p < 0.001); anti-MAA: 29%, 22%, 29%, and 53% (p < 0.001); and anti-AcVim: 20%, 17%, 38%, and 28% (p < 0.001). Total IgG levels also differed markedly, and when autoantibody levels were normalized to total IgG, differences between cohorts became less pronounced. Although there were some associations with AMPA and HLA risk alleles and smoking, none was consistent across all four cohorts. Conclusions: AMPA against various post-translational modifications could consistently be detected on different continents across ethnically diverse RA populations. Differences in AMPA levels corresponded to differences in total serum IgG levels. This suggests that, despite differences in risk factors, a common pathway may be involved in AMPA development across geographic locations and ethnicities. Show less
Moel, E.C. de; Trouw, L.A.; Terao, C.; Govind, N.; Tikly, M.; El-Gabalawy, H.; ... ; Woude, D. van der 2023
BackgroundRheumatoid arthritis (RA) occurs across the globe in different ethnic populations. Most RA patients harbor anti-modified protein antibodies (AMPA); however, it is unclear whether... Show moreBackgroundRheumatoid arthritis (RA) occurs across the globe in different ethnic populations. Most RA patients harbor anti-modified protein antibodies (AMPA); however, it is unclear whether differences exist in autoantibody responses at different geographic locations and between different ethnic groups, which could provide new clues regarding factors underlying autoantibody development. We therefore investigated AMPA prevalence and association with HLA DRB1 alleles and smoking in four ethnically diverse populations on four different continents.MethodsAnti-carbamylated (anti-CarP), anti-malondialdehyde acetaldehyde (anti-MAA), and anti-acetylated protein antibodies (anti-AcVim) IgG were determined in anti-citrullinated protein antibody-positive Dutch (NL, n = 103), Japanese (JP, n = 174), First Nations Peoples in Canada (FN, n = 100), and black South African (SA, n = 67) RA patients. Ethnicity-matched local healthy controls were used to calculate cut-offs. Risk factors associated with AMPA seropositivity in each cohort were identified using logistic regression.ResultsMedian AMPA levels were higher in First Nations Peoples in Canada and especially South African patients, as reflected by percentage seropositivity: NL, JP, FN, and SA: anti-CarP: 47%, 43%, 58%, and 76% (p < 0.001); anti-MAA: 29%, 22%, 29%, and 53% (p < 0.001); and anti-AcVim: 20%, 17%, 38%, and 28% (p < 0.001). Total IgG levels also differed markedly, and when autoantibody levels were normalized to total IgG, differences between cohorts became less pronounced. Although there were some associations with AMPA and HLA risk alleles and smoking, none was consistent across all four cohorts.ConclusionsAMPA against various post-translational modifications could consistently be detected on different continents across ethnically diverse RA populations. Differences in AMPA levels corresponded to differences in total serum IgG levels. This suggests that, despite differences in risk factors, a common pathway may be involved in AMPA development across geographic locations and ethnicities. Show less
Background: Predicting progression to clinical arthritis in individuals at-risk of developing rheumatoid arthritis is a prerequisite to developing stratification groups for prevention strategies.... Show moreBackground: Predicting progression to clinical arthritis in individuals at-risk of developing rheumatoid arthritis is a prerequisite to developing stratification groups for prevention strategies. Selecting accurate predictive criteria is the critical step to define the population at-risk. While positivity for anti-citrullinated protein antibodies (ACPA) remains the main recruitment biomarker, positivity for other autoantibodies (AutoAbs) identified before the onset of symptoms, may provide additional predictive accuracy for stratification.Objective: To perform a multiple AutoAbs analysis for both the prediction and the time of progression to inflammatory arthritis (IA).Methods: 392 individuals were recruited based on a new musculoskeletal complaint and positivity for ACPA or rheumatoid factor (RF). ELISAs were performed for ACPA, RF, anti-nuclear Ab, anti-carbamylated protein (anti-CarP) and anti-collagen AutoAbs. Logistic and COX regression were used for analysis.Results: Progression to IA was observed in 125/392 (32%) of cases, of which 78 progressed within 12 months. The AutoAbs ACPA, RF, anti-CarP were individually associated with progression (p<0.0001) and improved prediction when combined with demographic/clinical data (Accuracy >77%; area under the curve (AUC) >0.789), compared with prediction using only demographic/clinical data (72.9%, AUC=0.760). Multiple AutoAbs testing provided added value, with +6.4% accuracy for number of positive AutoAbs (AUC=0.852); +5.4% accuracy for AutoAbs levels (ACPA/anti-CarP, AUC=0.832); and +6.2% accuracy for risk-groups based on high/low levels (ACPA/RF/anti-CarP, AUC=0.837). Time to imminent progression was best predicted using ACPA/anti-CarP levels (AUC=0.779), while the number of positive AutoAbs was/status/risk were as good (AUC=0.778).Conclusion: We confirm added value of multiple AutoAbs testing for identifying progressors to clinical disease, allowing more specific stratification for intervention studies. Show less
Pattern recognition molecules (PRMs) form an important part of innate immunity, where they facilitate the response to infections and damage by triggering processes such as inflammation. The... Show morePattern recognition molecules (PRMs) form an important part of innate immunity, where they facilitate the response to infections and damage by triggering processes such as inflammation. The pentraxin family of soluble PRMs comprises long and short pentraxins, with the former containing unique N-terminal regions unrelated to other proteins or each other. No complete high-resolution structural information exists about long pentraxins, unlike the short pentraxins, where there is an abundance of both X-ray and cryoelectron microscopy (cryo-EM)-derived structures. This study presents a high-resolution structure of the prototypical long pentraxin, PTX3. Cryo-EM yielded a 2.5-angstrom map of the C-terminal pentraxin domains that revealed a radically different quaternary structure compared to other pentraxins, comprising a glycosylated D4 symmetrical octameric complex stabilized by an extensive disulfide network. The cryo-EM map indicated a-helices that extended N terminal of the pentraxin domains that were not fully resolved. AlphaFold was used to predict the remaining N-terminal structure of the octameric PTX3 complex, revealing two long tetrameric coiled coils with two hinge regions, which was validated using classification of cryo-EM two-dimensional averages. The resulting hybrid cryo-EM/AlphaFold structure allowed mapping of ligand binding sites, such as C1q and fibroblast growth factor-2, as well as rationalization of previous biochemical data. Given the relevance of PTX3 in conditions ranging from COVID-19 prognosis, cancer progression, and female infertility, this structure could be used to inform the understanding and rational design of therapies for these disorders and processes. Show less
Biewenga, M.; Heidt, S.; Vergunst, M.; Marijnissen, C.M.J.; Man, R.A.D.; Eijk, A.A.V.; ... ; Hoek, B.V. 2022
Background & Aims: Increased serum IgG and autoantibodies suggest involvement of B cells in autoimmune hepatitis (AIH). The aim of this study was to assess levels of B cell activating factor of... Show moreBackground & Aims: Increased serum IgG and autoantibodies suggest involvement of B cells in autoimmune hepatitis (AIH). The aim of this study was to assess levels of B cell activating factor of the tumour necrosis family (BAFF), IL-21, and circulating B cell populations in AIH and correlate these to treatment response.& nbsp;Methods: BAFF and IL-21 levels were determined in 66 patients with AIH before treatment and 10 healthy controls. Flow cytometry was performed on circulating B cells of 10 patients with AIH and 12 healthy controls.& nbsp;Results: Based on BAFF and IL-21 levels, untreated patients with AIH were divided into 3 groups: 27 (41%) patients with normal BAFF and IL-21 (normal BAFF), 27 (41%) patients with elevated BAFF but normal IL-21 (high BAFF), and 12 (18%) patients with elevated IL-21 (high IL-21). The high BAFF group presented with higher bilirubin compared with the normal BAFF and high IL-21 groups (159 vs. 26 vs. 89 lmol/L; p = 0.001; Mann-Whitney U test). After 12 months of treatment, 54% of the high BAFF group reached remission compared with 34% of the normal BAFF group and 0% of the high IL-21 group (p = 0.006, Chi-square test). During follow-up, 3 patients (25%) with high IL-21 developed primary sclerosing cholangitis (PSC) variant syndrome. Autoimmune-associated B cells were increased in patients with AIH compared with healthy controls (4.4 vs. 1.4%; p = 0.003, Mann-Whitney U test). BAFF levels were correlated positively with naive B cells (p = 0.01) and negatively with class-switched B cells (p = 0.003) and nonclass-switched B cells (p = 0.005, Spearman correlation).& nbsp;Discussion: Using BAFF and IL-21, we identified different immunological phenotypes of AIH with a different presentation, treatment response, and outcome. Patients with high IL-21 had the poorest treatment response and a risk of developing PSC variant syndrome. BAFF level was related to shifts in circulating B-cell populations.& nbsp;Lay summary: In patients with untreated autoimmune hepatitis (AIH), circulating B-cell activating factor of the tumour necrosis family (BAFF), IL-21, and B-cell populations were determined. Three subgroups were identified: with (1) normal BAFF and IL-21, (2) elevated BAFF and normal IL-21, and (3) elevated IL-21. Remission after 1-year treatment occurred in 54, 34, and 0% in Groups 1, 2, and 3, respectively. Group 2 had higher bilirubin, indicating more liver dysfunction. In 25% of patients with high IL-21, AIH-PSC variant syndrome developed, but none in the other groups. Autoimmune-associated B cells were elevated and BAFF levels correlated with certain B cells. (C) 2022 The Authors. Published by Elsevier B.V. on behalf of European Association for the Study of the Liver (EASL). Show less
Monahan, R.C.; Beukel, M.D. van den; Borggreven, N.V.; Fronczek, R.; Huizinga, T.W.J.; Kloppenburg, M.; ... ; Trouw, L.A. 2022
Background Although autoantibodies are an important hallmark of systemic lupus erythematosus (SLE), most are not specific for SLE or any of its clinical manifestations. Autoantibodies against post... Show moreBackground Although autoantibodies are an important hallmark of systemic lupus erythematosus (SLE), most are not specific for SLE or any of its clinical manifestations. Autoantibodies against post-translationally modified (PTM) proteins have been studied extensively in rheumatoid arthritis and associate with disease progression. While PTMs have also been detected in patients with SLE, studies on anti-PTM antibodies remain scarce. We studied the presence of anti-PTM antibodies in SLE and neuropsychiatric SLE (NPSLE), a manifestation that lacks serological markers. Methods IgG antibody responses against six PTMs (malondialdehyde-acetaldehyde adducts (MAA), advanced glycation end-products (AGE), carbamylation (CarP), citrullination, acetylation and nitration) were tested using ELISA in sera of 349 patients with SLE (mean age 44 +/- 13 years; 87% female) and compared with 108 healthy controls. Levels and positivity were correlated with clinical features and SLE manifestations. Results Anti-MAA, anti-AGE and anti-CarP antibodies were more prevalent in SLE compared with controls (MAA: 29% vs 3%, AGE: 18% vs 4%, CarP: 14% vs 5%, all p <= 0.0001). Anti-MAA and anti-AGE antibodies correlated with clinical manifestations and serological inflammatory markers. Patients with major NPSLE showed higher positivity of anti-MAA (39% vs 24%, p=0.01) and anti-CarP antibodies (20% vs 11%, p=0.04) than patients without major NPSLE. In addition, anti-PTM antibody levels correlated with brain volumes, an objective measure of nervous system involvement. Conclusions In our NPSLE cohort, a subset of patients with SLE have anti-PTM antibodies against MAA, AGE and CarP modified proteins. Interestingly, anti-MAA and anti-CarP were more prevalent in NPSLE, a manifestation for which no biomarkers exist. Show less
Dijkstra, D.J.; Lokki, A.I.; Gierman, L.M.; Borggreven, N.V.; Keur, C. van der; Eikmans, M.; ... ; Trouw, L.A. 2022
Preeclampsia (PE) generally manifests in the second half of pregnancy with hypertension and proteinuria. The understanding of the origin and mechanism behind PE is incomplete, although there is... Show morePreeclampsia (PE) generally manifests in the second half of pregnancy with hypertension and proteinuria. The understanding of the origin and mechanism behind PE is incomplete, although there is clearly an immune component to this disorder. The placenta constitutes a complicated immune interface between fetal and maternal cells, where regulation and tolerance are key. Stress factors from placental dysfunction in PE are released to the maternal circulation evoking the maternal response. Several complement factors play a role within this intricate landscape, including C1q in vascular remodeling and Factor H (FH) as the key regulator of alternative pathway complement activation. We hypothesize that decreased levels of C1q or FH, or disturbance of their function by autoantibodies, may be associated with PE. Autoantibodies against C1q and FH and the concentrations of C1q and FH were measured by ELISA in maternal sera from women with preeclamptic and normal pregnancies. Samples originated from cohorts collected in the Netherlands (n=63 PE; n=174 control pregnancies, n=51 nonpregnant), Finland (n=181 PE; n=63 control pregnancies) and Norway (n=59 PE; n=27 control pregnancies). Serum C1q and FH concentrations were higher in control pregnancy than in nonpregnant women. No significant differences were observed for serum C1q between preeclamptic and control pregnancy in any of the three cohorts. Serum levels of FH were lower in preeclamptic pregnancies compared to control pregnancies in two of the cohorts, this effect was driven by the early onset PE cases. Neither anti-C1q autoantibodies nor anti-FH autoantibodies levels differed between women with PE and normal pregnancies. In conclusion, levels of anti-C1q and anti-FH autoantibodies are not increased in PE. C1q and FH are increased in pregnancy, but importantly, a decrease in FH concentration is associated with PE. Show less
Bovenkamp, F.S. van de; Dijkstra, D.J.; Kooten, C. van; Gelderman, K.A.; Trouw, L.A. 2021
C1q is the recognition molecule of the classical pathway of the complement system. By binding to its targets, such as antigen-bound immunoglobulins or C-reactive protein, C1q contributes to the... Show moreC1q is the recognition molecule of the classical pathway of the complement system. By binding to its targets, such as antigen-bound immunoglobulins or C-reactive protein, C1q contributes to the innate defense against infections. However, C1q also plays several other roles beyond its traditional role in complement activation. Circulating levels of C1q are determined in routine diagnostics as biomarker in several diseases. Decreased C1q levels are present in several autoimmune conditions. The decreased levels reflect the consumption of C1q by complement activation and serves as a biomarker for disease activity. In contrast, increased C1q levels are present in infectious and inflammatory diseases and may serve as a diagnostic biomarker. The increased levels of C1q are still incompletely understood but are suggested to modulate the adaptive immune response as C1q is known to impact on the maturation status of antigen-presenting cells and C1q impacts directly on T cells leading to decreased T-cell activity in high C1q conditions. In this review, we provide a comprehensive overview of the current literature on circulating levels of C1q in health and disease, and discuss how C1q can both protect against infections as well as maintain tolerance by regulating adaptive immunity. Show less
Background Anti-modified protein antibodies (AMPA) targeting citrullinated, acetylated and/or carbamylated self-antigens are hallmarks of rheumatoid arthritis (RA). Although AMPA-IgG cross... Show moreBackground Anti-modified protein antibodies (AMPA) targeting citrullinated, acetylated and/or carbamylated self-antigens are hallmarks of rheumatoid arthritis (RA). Although AMPA-IgG cross-reactivity to multiple post-translational modifications (PTMs) is evident, it is unknown whether the first responding B cells, expressing IgM, display similar characteristics or if cross-reactivity is crucially dependent on somatic hypermutation (SHM). We now studied the reactivity of (germline) AMPA-IgM to further understand the breach of B cell tolerance and to identify if cross-reactivity depends on extensive SHM. Moreover, we investigated whether AMPA-IgM can efficiently recruit immune effector mechanisms. Methods Polyclonal AMPA-IgM were isolated from RA patients and assessed for cross-reactivity towards PTM antigens. AMPA-IgM B cell receptor sequences were obtained by single cell isolation using antigen-specific tetramers. Subsequently, pentameric monoclonal AMPA-IgM, their germline counterparts and monomeric IgG variants were generated. The antibodies were analysed on a panel of PTM antigens and tested for complement activation. Results Pentameric monoclonal and polyclonal AMPA-IgM displayed cross-reactivity to multiple antigens and different PTMs. PTM antigen recognition was still present, although reduced, after reverting the IgM into germline. Valency of AMPA-IgM was crucial for antigen recognition as PTM-reactivity significantly decreased when AMPA-IgM were expressed as IgG. Furthermore, AMPA-IgM was 15- to 30-fold more potent in complement-activation compared to AMPA-IgG. Conclusions We provide first evidence that AMPA-IgM are cross-reactive towards different PTMs, indicating that PTM (cross-)reactivity is not confined to IgG and does not necessarily depend on extensive somatic hypermutation. Moreover, our data indicate that a diverse set of PTM antigens could be involved in the initial tolerance breach in RA and suggest that AMPA-IgM can induce complement-activation and thereby inflammation. Show less
Vos, T.W. de; Winkelhorst, D.; Baelde, H.J.; Dijkstra, K.L.; Bergen, R.D.M. van; Meeren, L.E. van der; ... ; Haas, M. de 2021
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a disease that causes thrombocytopenia and a risk of bleeding in the (unborn) child that result from maternal alloantibodies directed... Show moreFetal and neonatal alloimmune thrombocytopenia (FNAIT) is a disease that causes thrombocytopenia and a risk of bleeding in the (unborn) child that result from maternal alloantibodies directed against fetal, paternally inherited, human platelet antigens (HPA). It is hypothesized that these alloantibodies can also bind to the placenta, causing placental damage. This study aims to explore signs of antibody-mediated placental damage in FNAIT. We performed a retrospective study that included pregnant women, their newborns, and placentas. It comprised 23 FNAIT cases, of which nine were newly diagnosed (14 samples) and 14 were antenatally treated with intravenous immune globulins (IVIg) (21 samples), and 20 controls, of which 10 had anti-HLA-class I antibodies. Clinical information was collected from medical records. Placental samples were stained for complement activation markers (C1q, C4d, SC5b-9, and mannose-binding lectin) using immunohistochemistry. Histopathology was examined according to the Amsterdam criteria. A higher degree of C4d deposition was present in the newly diagnosed FNAIT cases (10/14 samples), as compared to the IVIg-treated FNAIT cases (2/21 samples, p = 0.002) and anti-HLA-negative controls (3/20 samples, p = 0.006). A histopathological examination showed delayed maturation in four (44%) placentas in the newly diagnosed FNAIT cases, five (36%) in the IVIg-treated FNAIT cases, and one in the controls (NS). C4d deposition at the syncytiotrophoblast was present in combination with low-grade villitis of unknown etiology in three newly diagnosed FNAIT cases that were born SGA. We conclude that a higher degree of classical pathway-induced complement activation is present in placentas from pregnancies with untreated FNAIT. This may affect placental function and fetal growth. Show less
Objective: Autoantibodies (AutoAbs) have been observed in osteoarthritis (OA) with broad antigenicity, although their prevalence and role remain unclear. Post-translational modification (PTMs) of... Show moreObjective: Autoantibodies (AutoAbs) have been observed in osteoarthritis (OA) with broad antigenicity, although their prevalence and role remain unclear. Post-translational modification (PTMs) of proteins (oxidation, carbamylation, citrullination) is associated with synovitis and can lead to AutoAb development. Given the prevalence of synovitis, we explored whether AutoAbs to PTM-antigens are common in OA compared with rheumatoid arthritis (RA). Methods: Serum (n = 895) was obtained from healthy controls, OA and RA patients; and arthritic synovial fluid (SF, n = 290). ELISAs were used to quantify anti-citrullinated peptide (ACPA), anti-carbamylated protein (anti-CarP), anti-oxidized collagen (anti-ROS-CI/CII) antibodies.Results: In sera, positivity for PTM-antigens AutoAbs was observed at a lower frequency in OA with 64.1% (95%CI: 57.2-70.1%) more ACPA+ and 29.8% (21.0-37.3%) more anti-CarP + patients in RA (both P < 0.0001). Levels of ACPA, anti-CarP were also lower in OA (P < 0.0001). Anti-ROS-CII positivity was lower in OA compared to RA (16.6%, 4.8-28.6%) less frequent, P = 0.033) but not anti-native-CII. There was no impact of age/gender on AutoAbs associations with diseases either looking at positivity or levels. In SF, OA patients were often ACPA+ (45.9%) although less frequently than in RA (P = 0.004). Anti-CarP were rarely observed (<5% all samples). All collagen AutoAbs were more frequent in RA compared to OA (all P < 0.010) but only levels of anti-CII and anti-ROS-CII were significantly higher in they RA (P < 0.050).Conclusion: Although the frequency of AutoAbs for PTM proteins were lower in OA sera compared to RA, a higher proportion of OA SF were positive. The relative retention of AutoAbs in the OA joint requires further investigation.(c) 2021 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved. Show less
ObjectiveAntibodies targeting post-translationally modified proteins, such as anti-carbamylated protein antibodies (anti-CarP antibodies) are present in sera of rheumatoid arthritis (RA) patients.... Show moreObjectiveAntibodies targeting post-translationally modified proteins, such as anti-carbamylated protein antibodies (anti-CarP antibodies) are present in sera of rheumatoid arthritis (RA) patients. These autoantibodies associate with increased risk of RA development and with severity of joint destruction. It is not known which proteins in the RA joint are recognised by anti-CarP antibodies. Therefore, we investigated the presence and identity of carbamylated proteins in the human (inflamed) joint.MethodsWe obtained synovium, cartilage and synovial fluid from RA joints. Cartilage and synovium were obtained from controls. Samples were processed and used for immunohistochemistry or mass-spectrometric analysis to investigate the presence of carbamylated proteins. Anti-CarP antibody reactivity towards identified carbamylated proteins was tested by ELISA.ResultsImmunohistochemistry showed extensive staining of RA and control synovial tissue. Whole proteome analyses of the joint tissues revealed a large number of carbamylated peptidyllysine residues. We identified many carbamylated proteins in cartilage and were also able to detect carbamylation in synovial tissue and synovial fluid. Carbamylation was not exclusive to the RA joint and was also present in the joints of controls. Anti-CarP antibodies in the sera of RA patients were able to recognise the identified carbamylated proteins.ConclusionWe conclude that numerous carbamylated proteins are present in the RA joint. These carbamylated proteins can be recognised by anti-CarP antibodies, substantiating the notion that anti-CarP antibodies may play a role in the pathogenesis of RA. Show less
Objectives We aimed to determine the prevalence of anti-carbamylated protein (anti-CarP) antibodies in Mexican Hispanics with established rheumatoid arthritis (RA) and to assess their relationship... Show moreObjectives We aimed to determine the prevalence of anti-carbamylated protein (anti-CarP) antibodies in Mexican Hispanics with established rheumatoid arthritis (RA) and to assess their relationship with disease activity. Methods A cohort study was conducted in 278 patients with established RA during an 18-month follow-up. We measured IgG/IgM/IgA rheumatoid factor (RF), IgG anticitrullinated protein antibodies (ACPA) and IgG/IgM/IgA anti-CarP antibodies using enzyme-linked immunosorbent assay (ELISA). For disease activity, we performed the 28-joint disease activity score with erythrocyte sedimentation rate (DAS28-ESR). Repeated measures one-way ANOVA was used to test the association between anti-CarP IgG antibody status and longitudinal DAS28-ESR scores. Patients were evaluated at baseline and at 6, 12, and 18 months during follow-up. Results Anti-CarP IgG antibodies were positive in 47.8% of patients and, accounting for all isotypes, in 9.5% of patients with negative RF and ACPA. Triple antibody positivity was present in 42.6% of patients in our sample. Anti-CarP IgG antibody positivity did not show statistically significant differences in mean DAS28-ESR when compared to anti-CarP IgG antibody negative patients at baseline, 6, 12 or 18 months. Conclusion Anti-CarP IgG antibodies are not associated to a higher disease activity in Hispanic patients with established RA. Our findings suggest that the clinical value of measuring anti-CarP antibodies in RA diminishes over time. Show less
Regueiro, C.; Casares-Marfil, D.; Lundberg, K.; Knevel, R.; Acosta-Herrera, M.; Rodriguez-Rodriguez, L.; ... ; Gonzalez, A. 2021
Objective. Previously, only the HLA-DRB1 alleles have been assessed in rheumatoid arthritis (RA). The aim of the present study was to identify the key major histocompatibility complex (MHC)... Show moreObjective. Previously, only the HLA-DRB1 alleles have been assessed in rheumatoid arthritis (RA). The aim of the present study was to identify the key major histocompatibility complex (MHC) susceptibility factors showing a significant association with anti-carbamylated protein antibody-positive (anti-CarP+) RA.Methods. Analyses were restricted to RA patients who were anti-cyclic citrullinated peptide antibody negative (anti-CCP), because the anti-CCP status dominated the results otherwise. Therefore, we studied samples from 1,821 anti-CCP- RA patients and 6,821 population controls from Spain, Sweden, and the Netherlands. The genotypes for similar to 8,000 MHC biallelic variants were assessed by dense genotyping and imputation. Their association with the anti-CarP status in RA patients was tested with logistic regression and combined with inverse-variance meta-analysis. Significance of the associations was assessed according to a study-specific threshold of P < 2.0 x 10(-5).Results. The HLA-B*08 allele and its correlated amino acid variant Asp-9 showed a significant association with anti-CarP+/anti-CCP- RA (P < 3.78 x 10(-7); I-2 = 0). This association was specific when assessed relative to 3 comparator groups: population controls, anti-CarP-/anti-CCP- RA patients, and anti-CCP- RA patients who were positive for other anti-citrullinated protein antibodies. Based on these findings, anti-CarP+/anti-CCP- RA patients could be separated from other antibody-defined subsets of RA patients in whom an association with the HLA-B*08 allele has been previously demonstrated. No other MHC variant remained associated with anti-CarP+/anti-CCP- RA after accounting for the presence of the HLA-B*08 allele. Specifically, the reported association of HLA-DRB1*03 was observed at a level comparable to that reported previously, but it was attributable to linkage disequilibrium.Conclusion. These results identify HLA-B*08 carrying Asp-9 as the MHC locus showing the strongest association with anti-CarP+/anti-CCP- RA. This knowledge may help clarify the role of the HLA in susceptibility to specific subsets of RA, by shaping the spectrum of RA autoantibodies. Show less
