Publications by authors named "Rene E M Toes"

253 Publications

Light chain skewing in autoantibodies and B-cell receptors of the citrullinated antigen-binding B-cell response in rheumatoid arthritis.

PLoS One 2021 30;16(3):e0247847. Epub 2021 Mar 30.

Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.

Rheumatoid arthritis (RA) is a chronic autoimmune disease affecting 1% of the world population. RA is associated with the presence of autoantibodies, of which anti-citrullinated protein antibodies (ACPA) are most prominent. ACPA are produced by citrullinated antigen-binding B cells that have presumably survived tolerance checkpoints. So far, it is unclear how and when such autoreactive B cells emerge. Light chain (LC) rearrangement and mutation rates can be informative with regard to selection steps during B-cell development. Therefore, we studied LC characteristics of ACPA-expressing B cells and secreted ACPA with the aim to better understand the development of this disease-specific, autoreactive B-cell response. Paired ACPA-IgG and ACPA-depleted IgG were isolated from serum (n = 87) and synovial fluid (SF, n = 21) of patients with established RA. We determined the LC composition for each fraction by ELISA using kappa(Igκ)- and lambda(Igλ) LC-specific antibodies. Cellular LC expression was determined using flow cytometry. In addition, we used a B-cell receptor (BCR)-specific PCR to obtain LC variable region sequences of citrullinated antigen- and tetanus toxoid (TT)-binding B cells. In serum, we observed an increased frequency of lambda LC in ACPA-IgG (1.64:1) compared to control IgG (2.03:1) and to the κ/λ ratio reported for healthy individuals (2:1). A similar trend towards higher frequencies of lambda LCs was observed for ACPA-IgG in SF (1.84:1). Additionally, the percentage of Igλ-expressing B cells was higher for citrullinated antigen-binding B cells (51%) compared to TT-specific (43%) and total CD19+CD20+ B cells (36%). Moreover, an increased Igλ percentage was observed in BCR-sequences derived from ACPA-expressing (49%) compared to TT-specific B cells (34%). Taken together, we report an enhanced frequency of lambda LCs in the secreted ACPA-IgG repertoire and, on the cellular level, in BCR sequences of ACPA-expressing B cells compared to control. This skewing in the autoreactive B-cell repertoire could reflect a process of active selection.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247847PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8009422PMC
March 2021

Onset of rheumatoid arthritis after COVID-19: coincidence or connected?

Ann Rheum Dis 2021 Mar 1. Epub 2021 Mar 1.

Department of Rheumatology, Leiden University Medical Center, Leiden, Zuid-Holland, The Netherlands.

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http://dx.doi.org/10.1136/annrheumdis-2021-219859DOI Listing
March 2021

Persistently activated, proliferative memory autoreactive B cells promote inflammation in rheumatoid arthritis.

Sci Transl Med 2020 11;12(570)

Department of Rheumatology, Leiden University Medical Center, 2300RC Leiden, Netherlands.

Autoreactive B cells mediate autoimmune pathology, but exactly how remains unknown. A hallmark of rheumatoid arthritis (RA), a common autoimmune disease, is the presence of disease-specific anticitrullinated protein antibodies (ACPAs). Here, we showed that ACPA-positive B cells in patients with RA strongly expressed T cell-stimulating ligands, produced abundant proinflammatory cytokines, and were proliferative while escaping inhibitory signals. This activated state was found at different degrees in different stages of disease: highest in patients with recent-onset RA, moderate in patients with established RA, and far less pronounced in ACPA-positive individuals "at risk" for developing disease. The activated autoreactive B cell response persisted in patients who achieved clinical remission with conventional treatment. ACPA-positive B cells in blood and synovial fluid secreted increased amounts of the chemoattractant interleukin-8, which attracted neutrophils, the most abundant immune cell in arthritic joints. Tetanus toxoid-specific B cells from the same patients exhibited properties of memory B cells without the activation and proliferation phenotype, but these cells transiently acquired a similar proliferative phenotype upon booster vaccination. Together, these data indicated that continuous antigenic triggering of autoreactive B cells occurs in human autoimmune disease and support the emerging concept of immunological activity that persists under treatment even in clinical remission, which may revise our current concept of treatment targets for future therapeutic interventions. In addition, our data pointed to a pathogenic role of ACPA-positive B cells in the inflammatory disease process underlying RA and favor approaches that aim at their antigen-specific inactivation or depletion.
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http://dx.doi.org/10.1126/scitranslmed.aaz5327DOI Listing
November 2020

Anti-Inflammatory and Proresolving Effects of the Omega-6 Polyunsaturated Fatty Acid Adrenic Acid.

J Immunol 2020 11 2;205(10):2840-2849. Epub 2020 Oct 2.

Department of Rheumatology, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands.

Polyunsaturated fatty acids (PUFAs) and their metabolites are potent regulators of inflammation. Generally, omega ()-3 PUFAs are considered proresolving whereas -6 PUFAs are classified as proinflammatory. In this study, we characterized the inflammatory response in murine peritonitis and unexpectedly found the accumulation of adrenic acid (AdA), a poorly studied -6 PUFA. Functional studies revealed that AdA potently inhibited the formation of the chemoattractant leukotriene B (LTB), specifically in human neutrophils, and this correlated with a reduction of its precursor arachidonic acid (AA) in free form. AdA exposure in human monocyte-derived macrophages enhanced efferocytosis of apoptotic human neutrophils. In vivo, AdA treatment significantly alleviated arthritis in an LTB-dependent murine arthritis model. Our findings are, to our knowledge, the first to indicate that the -6 fatty acid AdA effectively blocks production of LTB by neutrophils and could play a role in resolution of inflammation in vivo.
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http://dx.doi.org/10.4049/jimmunol.1801653DOI Listing
November 2020

Mass-spectrometric identification of carbamylated proteins present in the joints of rheumatoid arthritis patients and controls.

Clin Exp Rheumatol 2020 Sep 1. Epub 2020 Sep 1.

Department of Rheumatology, Leiden University Medical Center, and Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, The Netherlands.

Objectives: Antibodies targeting post-translationally modified proteins, such as anti-carbamylated protein antibodies (anti-CarP antibodies) are present in the 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.

Methods: We 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.

Results: Immunohistochemistry 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.

Conclusions: We 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.
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September 2020

Association of Anti-Topoisomerase I Antibodies of the IgM Isotype With Disease Progression in Anti-Topoisomerase I-Positive Systemic Sclerosis.

Arthritis Rheumatol 2020 11 29;72(11):1897-1904. Epub 2020 Sep 29.

Leiden University Medical Center, Leiden, The Netherlands.

Objective: Anti-topoisomerase I (anti-topo I) autoantibodies in systemic sclerosis (SSc) are associated with diffuse skin involvement and interstitial lung fibrosis. Thus far, however, the relationship between anti-topo I antibody response and disease course has not yet been fully evaluated. This study was undertaken to gain insight into the association between characteristics of the anti-topo I antibody response and clinical disease course in SSc patients positive for anti-topo I antibodies.

Methods: Levels of anti-topo I IgG, anti-topo I IgM, and anti-topo I IgA were assessed in consecutive serum samples obtained from patients at baseline who were positive for anti-topo I IgG in the Leiden Combined Care In Systemic Sclerosis (CCISS) cohort. One-year disease progression was defined by a relevant increase in modified Rodnan skin thickness score (MRSS), decline in pulmonary function, development of digital ulcers, renal crisis, and pulmonary hypertension, and/or mortality. Validation was performed in SSc patients who were positive for anti-topo I from the Oslo University Hospital and University Hospital Zurich.

Results: Of the 103 patients with anti-topo I IgG in the CCISS cohort, clinical data were available to assess 1-year disease progression in 81 patients. Of these 81 patients, 23 (28%) had disease progression. At baseline, patients with disease progression were significantly more often anti-topo I IgM-positive than those who did not experience disease progression (21 [91%] of 23 versus 33 [57%] of 58; P < 0.01). This finding was confirmed in the independent validation samples.

Conclusion: In SSc patients who were anti-topo I IgG-positive, presence of anti-topo I IgM, which might be considered as a surrogate for an ongoing autoreactive B cell immune response, is associated with disease progression.
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http://dx.doi.org/10.1002/art.41403DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7702063PMC
November 2020

Templated insertions at VD and DJ junctions create unique B-cell receptors in the healthy B-cell repertoire.

Eur J Immunol 2020 12 27;50(12):2099-2101. Epub 2020 Aug 27.

Department of Hematology, Leiden University Medical Center, Leiden, The Netherlands.

RAG complexes recognise (cryptic) RSS sites both in and outside immunoglobulin sites. Excision circles may be reinserted into V(D)J rearrangements as long templated insertions to diversify the adaptive immune repertoire. We show that such VDJ with templated insertions are incidentally found in the repertoire of healthy donors.
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http://dx.doi.org/10.1002/eji.202048828DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7754338PMC
December 2020

Arthritis autoantibodies in individuals without rheumatoid arthritis: follow-up data from a Dutch population-based cohort (Lifelines).

Rheumatology (Oxford) 2021 02;60(2):658-666

Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.

Objectives: To assess whether the presence of arthritis autoantibodies alongside IgG ACPA predicts clinically suspect arthralgia in ACPA-positive subjects without RA.

Methods: In the population-based Lifelines cohort (n = 40 136), 308 IgG ACPA-positive individuals without RA were present. Serum levels of IgA ACPA, IgA and IgM RF, and IgG anti-carbamylated antibodies were measured at baseline. Individuals were divided based on the Connective tissue disease Screening Questionnaire after 2 years follow-up. Antibodies to Porphyromonas gingivalis were determined at baseline and related to presence of periodontitis and joint complaints at 2 years follow-up.

Results: Of 308 subjects 53.6% were also seropositive for IgA ACPA, 42.2% for IgM RF, 23.7% for IgA RF and 13.6% for anti-carbamylated antibodies. We defined 75 persons with clinically suspect arthralgia at risk for RA based on CTD Screening Questionnaire at follow-up. Significantly more seropositivity for IgM RF and higher levels of IgG ACPA, IgA ACPA and IgM RF were found in clinically suspect arthralgia compared with no-clinically suspect arthralgia. In multivariate logistic regression correcting for age, gender and never smoking, positivity for three or more extra autoantibodies was significantly associated with clinically suspect arthralgia. Although levels of anti-P. gingivalis were not different between groups, they were significantly correlated to levels of both RFs, and both ACPAs in clinically suspect arthralgia.

Conclusions: ACPA-positive individuals without RA who develop clinically suspect arthralgia have more and higher levels of other arthritis autoantibodies at baseline. Levels of anti-P. gingivalis are not related to self-reported periodontitis or clinically suspect arthralgia, but are correlated to arthritis autoantibodies in clinically suspect arthralgia.
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http://dx.doi.org/10.1093/rheumatology/keaa219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7850523PMC
February 2021

Association Between Centromere- and Topoisomerase-specific Immune Responses and the Degree of Microangiopathy in Systemic Sclerosis.

J Rheumatol 2020 Jun 1. Epub 2020 Jun 1.

C.M. Wortel received a scholarship from ReumaNederland. N.M. van Leeuwen, MD, C.M. Wortel, MSc, C.M. Fehres, PhD, H.U. Scherer, MD, PhD, R.E.M Toes, Professor, MSc, PhD, T.W. Huizinga, Professor, MD, PhD, J.K. de Vries-Bouwstra, MD, PhD, Department of Rheumatology, Leiden University Medical Center; J.A. Bakker, MSc, PhD, Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, the Netherlands. All authors have declared that they have no conflicts of interest. Address correspondence to Dr. N.M. van Leeuwen, Department of Rheumatology, Leiden University Medical Center, C1-R, PO Box 9600, 2300 RC, Leiden, the Netherlands. Email: Accepted for publication May 13, 2020.

Objective: Autoreactive antibody responses, including the use of several isotypes of autoantibodies, have been shown to be associated with clinical outcome in several rheumatic autoimmune diseases. The goals of this study were to evaluate whether (1) anticentromere antibody (ACA)- and antitopoisomerase antibody (ATA)-specific isotype expression, and (2) organ involvement are associated with the degree of microangiopathy in systemic sclerosis (SSc).

Methods: ACA and ATA IgG, IgM, and IgA levels were measured in baseline serum samples of ACA IgG-positive (+) and ATA IgG+ patients with SSc. The degree of microangiopathy was determined based on nailfold videocapillaroscopy (NVC) images collected at the same point in time. Logistic regression analyses with autoantibodies, clinical characteristics, isotype expression, and ACA and ATA IgG, IgM, and IgA levels as independent variables, and NVC pattern as the dependent variable were performed.

Results: In 164 patients, isotype levels and degree of microangiopathy were evaluated. Logistic regression confirmed the association of the degree of microangiopathy with the presence of digital ulcers (OR 3.07, 95% CI 1.43-6.60), interstitial lung disease (OR 3.41, 95% CI 1.11-10.61), and pulmonary arterial hypertension (OR 5.58, 95% CI 2.05-17.81). ATA positivity was associated with more severe microangiopathy (OR 2.09, 95% CI 1.05-4.13). Patients who expressed solely ACA IgG showed a trend towards less severe microangiopathy compared to patients also expressing ACA IgM and/or IgA. Levels of ACA IgG and ATA IgM were found to be associated with microangiopathy severity.

Conclusion: We observed an association between ACA and ATA responses and the degree of microangiopathy in SSc. These findings might indicate that the breadth of the autoimmune response, as reflected by autoantibody production and microvascular damage, interacts in the pathophysiology of SSc.
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http://dx.doi.org/10.3899/jrheum.191331DOI Listing
June 2020

Toll-like receptor signaling induces a temporal switch towards a resolving lipid profile in monocyte-derived macrophages.

Biochim Biophys Acta Mol Cell Biol Lipids 2020 09 21;1865(9):158740. Epub 2020 May 21.

Leiden University Medical Center, Department of Rheumatology, Leiden, the Netherlands.

Inflammation is a tightly regulated process. During the past decade it has become clear that the resolution of inflammation is an active process and its dysregulation can contribute to chronic inflammation. Several cells and soluble mediators, including lipid mediators, regulate the course of inflammation and its resolution. It is, however, unclear which signals and cells are involved in initiating the resolution process. Macrophages are tissue resident cells and key players in regulating tissue inflammation through secretion of soluble mediators, including lipids. We hypothesize that persistent inflammatory stimuli can initiate resolution pathways in macrophages. In this study, we detected 21 lipids in LPS-stimulated human monocyte-derived macrophages by liquid chromatography coupled to tandem mass spectrometry. Cyclooxygenase-derived Prostaglandins were observed in the first six hours of stimulation. Interestingly, a switch towards 15-lipoxygenase products, such as the pro-resolving lipid precursors 15-HEPE and 17-HDHA was observed after 24 h. The RNA and protein expression of cyclooxygenase and 15-lipoxygenase were in line with this trend. Treatment with 17-HDHA increased IL-10 production of monocyte-derived macrophages and decreased LTB production by neutrophils, indicating the anti-inflammatory property of this lipid. These data reveal that monocyte-derived macrophages contribute to the resolution of inflammation in time by the production of pro-resolving lipids after an initial inflammatory stimulus.
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http://dx.doi.org/10.1016/j.bbalip.2020.158740DOI Listing
September 2020

A Comparison of Immunoglobulin Variable Region N-Linked Glycosylation in Healthy Donors, Autoimmune Disease and Lymphoma.

Front Immunol 2020 18;11:241. Epub 2020 Feb 18.

Department of Rheumatology, Leiden University Medical Center, Leiden, Netherlands.

N-linked glycans play an important role in immunity. Although the role of N-linked glycans in the Fragment crystallizable (Fc) region of immunoglobulins has been thoroughly described, the function of N-linked glycans present in Ig-variable domains is only just being appreciated. Most of the N-linked glycans harbored by immunoglobulin variable domain are of the complex biantennary type and are found as a result of the presence of N-linked glycosylation that most often have been introduced by somatic hypermutation. Furthermore, these glycans are ubiquitously present on autoantibodies observed in some autoimmune diseases as well as certain B-cell lymphomas. For example, variable domain glycans are abundantly found by anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) as well as by the B-cell receptors of follicular lymphoma (FL). In FL, variable domain glycans are postulated to convey a selective advantage through interaction with lectins and/or microbiota, whereas the contribution of variable domain glycans on autoantibodies is not known. To aid the understanding how these seemingly comparable phenomena contribute to a variety of deranged B-responses in such different diseases this study summarizes the characteristics of ACPA and other auto-antibodies with FL and healthy donor immunoglobulins, to identify the commonalities and differences between variable domain glycans in autoimmune and malignant settings. Our finding indicate intriguing differences in variable domain glycan distribution, frequency and glycan composition in different conditions. These findings underline that variable domain glycosylation is a heterogeneous process that may lead to a number of pathogenic outcomes. Based on the current body of knowledge, we postulate three disease groups with distinct variable domain glycosylation patterns, which might correspond with distinct underlying pathogenic processes.
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http://dx.doi.org/10.3389/fimmu.2020.00241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040075PMC
March 2021

Circulating calprotectin (S100A8/A9) is higher in rheumatoid arthritis patients that relapse within 12 months of tapering anti-rheumatic drugs.

Arthritis Res Ther 2019 12 5;21(1):268. Epub 2019 Dec 5.

Department of Rheumatology, Leiden University Medical Center, Leiden, the Netherlands.

Objective: To investigate whether calprotectin (S100A8/A9 or MRP8/14), an inflammatory complex released by monocytes, could indicate residual subclinical inflammation in rheumatoid arthritis (RA) patients who are in stable remission on disease-modifying anti-rheumatic drugs (DMARDs) and serve as a marker for disease flare after DMARD tapering.

Methods: We used data from two trials. Patients from the IMPROVED study had early (< 2 years) RA, and when they achieved disease activity score remission (DAS44 < 1.6), they stopped methotrexate to attempt drug-free remission. Patients from the RETRO study had established RA in stable remission (DAS28 < 2.6) and either tapered by 50% or stopped (biological or conventional) DMARDs. Circulating calprotectin at the tapering time point was determined by ELISA, and its predictive value for flare (loss of remission) within 12 months of DMARD tapering/stopping was determined.

Results: In both IMPROVED (n = 104) and RETRO (n = 57), patients that flared within 12 months had higher calprotectin at the moment of DMARD tapering/stopping. Twofold higher calprotectin at the moment of DMARD tapering/stopping was associated with an increased risk (odds ratio) of flare of 1.07 (95% CI 0.98-1.18, p = 0.14) in the IMPROVED and 3.62 (95% CI 1.76-7.46, p < 0.001) in the RETRO. Correcting for clinical predictors of flare (DAS at study inclusion, anti-CCP2 positivity, gender) did not change these estimates. The area under the receiver operating curve of calprotectin levels for predicting flare within 12 months was 0.63 (95% CIs 0.51-0.76) in the IMPROVED study and 0.80 (95% CIs 0.69 to 0.92) in the RETRO study.

Conclusion: Circulating calprotectin levels in RA patients in remission on DMARDs are higher in patients that will flare upon DMARD tapering/stopping. Since the differences between the cohorts precluded definitive conclusions, more research is needed to determine whether calprotectin has prognostic value in predicting flare after attempting drug tapering in RA.

Trial Registration: IMPROVED, ISRCTN11916566. RETRO, 2009-015740-42.
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http://dx.doi.org/10.1186/s13075-019-2064-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6894482PMC
December 2019

-Glycosylation Site Analysis of Citrullinated Antigen-Specific B-Cell Receptors Indicates Alternative Selection Pathways During Autoreactive B-Cell Development.

Front Immunol 2019 4;10:2092. Epub 2019 Sep 4.

Department of Rheumatology, Leiden University Medical Center, Leiden, Netherlands.

Many autoimmune diseases are hallmarked by autoreactive B and plasma cell responses that are directly or indirectly involved in disease pathogenesis. These B-cell responses show large variability between diseases, both in terms of the secreted autoantibody repertoire and the dynamics and characteristics of the underlying B-cell responses. Hence, different mechanisms have been proposed to explain the emergence of autoreactive B cells in an otherwise self-tolerant immune system. Notably, most mechanistic insights have been obtained from murine studies using models harboring genetic modifications of B and T cells. Given recent technological advances that have rendered autoreactive human B cells accessible for analysis, we here discuss the phenomenon of extensive -glycosylation of the B-cell receptor (BCR) variable domain of a prototypic human autoreactive B-cell response and its potential role in the generation of autoimmunity. Anti-citrullinated protein antibodies (ACPA) hallmark the most disease-specific autoimmune response in Rheumatoid Arthritis (RA). Remarkably, ACPA-IgG are heavily -glycosylated in the variable domain due to somatic mutations that generate abundant -glycosylation consensus sequences. These sites, obtained from full-length BCR sequences of ACPA-expressing B cells from 12 ACPA-positive RA patients, were here analyzed in detail. Sites that required a single nucleotide mutation to be generated were defined as single somatic hypermutation (s-SHM) sites, whereas sites requiring multiple mutations were defined as m-SHM sites. IgG sequences of 12 healthy donors were used as control. Computational modeling of the germinal center reaction (CLONE algorithm) was used with the germline counterparts of ACPA-IgG heavy chain (HC) sequences to simulate the germinal center response. Our analyses revealed an abundance of -glycosylation sites in ACPA-IgG HC that frequently required multiple mutations and predominated in specific positions. Based on these data, and taking into account recent insights into the dynamics of the ACPA-response during disease development, we here discuss the hypothesis that -glycosylation sites in ACPA-IgG variable domains could lead to alternative, possibly antibody affinity-independent selection forces. Presumably, this occurs during germinal center responses allowing these B cells to escape from putative tolerance checkpoints, thereby driving autoreactive B cell development in the pathogenesis of RA.
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http://dx.doi.org/10.3389/fimmu.2019.02092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6749139PMC
November 2020

Ligandomes obtained from different HLA-class II-molecules are homologous for N- and C-terminal residues outside the peptide-binding cleft.

Immunogenetics 2019 09 13;71(8-9):519-530. Epub 2019 Sep 13.

Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.

Human CD4+ T lymphocytes play an important role in inducing potent immune responses. T cells are activated and stimulated by peptides presented in human leucocyte antigen (HLA)-class II molecules. These HLA-class II molecules typically present peptides of between 12 and 20 amino acids in length. The region that interacts with the HLA molecule, designated as the peptide-binding core, is highly conserved in the residues which anchor the peptide to the molecule. In addition, as these peptides are the product of proteolytic cleavages, certain conserved residues may be expected at the N- and C-termini outside the binding core. To study whether similar conserved residues are present in different cell types, potentially harbouring different proteolytic enzymes, the ligandomes of HLA-DRB1*03:01/HLA-DRB > 1 derived from two different cell types (dendritic cells and EBV-transformed B cells) were identified with mass spectrometry and the binding core and N- and C-terminal residues of a total of 16,568 peptides were analysed using the frequencies of the amino acids in the human proteome. Similar binding motifs were found as well as comparable conservations in the N- and C-terminal residues. Furthermore, the terminal conservations of these ligandomes were compared to the N- and C-terminal conservations of the ligandome acquired from dendritic cells homozygous for HLA-DRB1*04:01. Again, comparable conservations were evident with only minor differences. Taken together, these data show that there are conservations in the terminal residues of peptides, presumably the result of the activity of proteases involved in antigen processing.
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http://dx.doi.org/10.1007/s00251-019-01129-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6790208PMC
September 2019

Different classes of anti-modified protein antibodies are induced on exposure to antigens expressing only one type of modification.

Ann Rheum Dis 2019 07 31;78(7):908-916. Epub 2019 May 31.

Department of Rheumatology, Leids Universitair Medisch Centrum, Leiden, The Netherlands.

Objectives: Autoantibodies against post-translationally modified proteins (anti-modified protein antibodies or AMPAs) are a hallmark of rheumatoid arthritis (RA). A variety of classes of AMPAs against different modifications on proteins, such as citrullination, carbamylation and acetylation, have now been described in RA. At present, there is no conceptual framework explaining the concurrent presence or mutual relationship of different AMPA responses in RA. Here, we aimed to gain understanding of the co-occurrence of AMPA by postulating that the AMPA response shares a common 'background' that can evolve into different classes of AMPAs.

Methods: Mice were immunised with modified antigens and analysed for AMPA responses. In addition, reactivity of AMPA purified from patients with RA towards differently modified antigens was determined.

Results: Immunisation with carbamylated proteins induced AMPAs recognising carbamylated proteins and also acetylated proteins. Similarly, acetylated proteins generated (autoreactive) AMPAs against other modifications as well. Analysis of anti-citrullinated protein antibodies from patients with RA revealed that these also display reactivity to acetylated and carbamylated antigens. Similarly, anti-carbamylated protein antibodies showed cross-reactivity against all three post-translational modifications.

Conclusions: Different AMPA responses can emerge from exposure to only a single type of modified protein. These findings indicate that different AMPA responses can originate from a common B-cell response that diversifies into multiple distinct AMPA responses and explain the presence of multiple AMPAs in RA, one of the hallmarks of the disease.
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http://dx.doi.org/10.1136/annrheumdis-2018-214950DOI Listing
July 2019

N-Linked Glycans in the Variable Domain of IgG Anti-Citrullinated Protein Antibodies Predict the Development of Rheumatoid Arthritis.

Arthritis Rheumatol 2019 10 2;71(10):1626-1633. Epub 2019 Sep 2.

Leiden University Medical Center, Leiden, The Netherlands.

Objective: Anti-citrullinated protein antibodies (ACPAs) are disease-specific biomarkers in rheumatoid arthritis (RA). More than 90% of IgG ACPAs harbor N-linked glycans in the antibody variable (V) domain. The corresponding N-glycosylation sites in ACPA V-region sequences result from somatic hypermutation, a T cell-dependent process. As ample evidence indicates that T cells drive the maturation of the ACPA response prior to arthritis onset, we undertook this study to investigate whether the presence of glycans in IgG ACPA V domains predicts the transition from predisease autoimmunity to overt RA.

Methods: We analyzed 2 independent sets of serum samples obtained from 126 ACPA-positive first-degree relatives (FDRs) of RA patients. Both sets originated from an Indigenous North American population and comprised cross-sectional and longitudinal samples of individuals who did or did not develop inflammatory arthritis. Serum IgG ACPAs were affinity-purified and subjected to ultra high-performance liquid chromatography-based glycan analysis.

Results: In both data sets, FDR-derived IgG ACPA displayed markedly lower levels of V domain glycans (<50%) compared to IgG ACPA from RA patients. Notably, FDRs who later developed RA showed extensive V-domain glycosylation before the onset of arthritis. Moreover, IgG ACPA V-domain glycosylation was strongly associated with future development of RA (hazard ratio 6.07 [95% confidence interval 1.46-25.2]; P = 0.013).

Conclusion: Extensive glycosylation of the IgG ACPA V domain is present in a subset of predisposed FDRs of Indigenous North American RA patients. The presence of this feature substantially increases the risk of RA development. Based on these findings, we propose that glycosylation of the IgG ACPA V domain represents a predictive marker for RA development in ACPA-positive individuals and may serve to better target prevention measures.
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http://dx.doi.org/10.1002/art.40920DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6790576PMC
October 2019

In rheumatoid arthritis, changes in autoantibody levels reflect intensity of immunosuppression, not subsequent treatment response.

Arthritis Res Ther 2019 01 18;21(1):28. Epub 2019 Jan 18.

Leiden University Medical Center, Leiden, the Netherlands.

Background: Rheumatoid arthritis (RA) is characterized by the presence of autoantibodies like rheumatoid factor (RF), anti-cyclic citrullinated peptide-2 (anti-CCP2), and anti-carbamylated protein (anti-CarP) antibodies. It is currently unclear whether changes in autoantibody levels are associated with disease activity/treatment outcomes and whether they are modified by treatment intensity. Therefore, we determined longitudinal changes in RA-autoantibody levels, the association between these changes and activity score (DAS) and treatment outcomes, and the effect of intensity of immunosuppressive treatment on levels.

Methods: In 381 seropositive RA patients from the IMPROVED study, we measured IgG, IgM, and IgA of anti-CCP2 and anti-CarP; IgM and IgA of RF; and IgG against four citrullinated and two acetylated peptides at 4-month intervals over the first year of treatment. Following initial prednisone and methotrexate (MTX), treatment was changed every 4 months aiming for DAS < 1.6. We investigated changes in autoantibody levels following treatment escalation versus tapering, and the association of levels with DAS over time, EULAR response, and drug-free remission (DFR) ≥ 1 year.

Results: For all 14 autoantibodies, levels decreased from 0 to 4 months and then rose until 12 months. Following treatment escalation, autoantibody levels dropped markedly, while they rose following tapering: RF IgM levels, a representative autoantibody, dropped 10% after restarting prednisone and rose 15% aU/mL after tapering MTX (p < 0.0001). There was no association between autoantibody levels and DAS over time or EULAR response. Greater relative changes between 0 and 12 months did not predict DFR (0-12-month relative change RF IgM, - 39% for no DFR (n = 126) and - 16% for DFR (n = 18)).

Conclusions: Changes in RA-autoantibody levels are not associated with DAS or long-term treatment response, but reflect intensity of immunosuppression. This suggests that autoantibody levels are modifiable by current therapies, but that modifying levels is in itself of limited clinical relevance.

Trial Registration: ISRCTN11916566 . Registered on 7 November 2006.
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http://dx.doi.org/10.1186/s13075-019-1815-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339446PMC
January 2019

Altered composition and phenotype of mucosal-associated invariant T cells in early untreated rheumatoid arthritis.

Arthritis Res Ther 2019 01 5;21(1). Epub 2019 Jan 5.

Department of Rheumatology, Leiden University Medical Center, PO Box 9600 (Zone C1-R), Albinusdreef 2, 2233 ZA, Leiden, the Netherlands.

Background: Mucosal-associated invariant T (MAIT) cells are innate-like T cells that recognise bacterial metabolites presented by MHC class I-related protein 1 (MR1). Bacterial dysbiosis has been implicated in auto-inflammatory disease development. We investigated MAIT cells in early, untreated rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients.

Methods: Blood and synovial fluid mononuclear cells obtained from patients (SpA/RA) and controls were stimulated with fixed Escherichia coli to provide MAIT ligand. Cells were analysed by flow cytometry and MAIT cells were identified by MR1-5-OP-RU tetramers. Synovial biopsies were studied by confocal microscopy.

Results: Peripheral and synovial CD3 MR1-tet MAIT cell frequencies were comparable in all groups. MAIT cells were detected in RA and SpA synovium based on CD3, CD161 and Vα7.2 expression. Peripheral RA MAIT cells were mostly CD4 (controls 8.3%, SpA 12.3%, RA 52.6%; p < 0.001) and CD161 expression was strongly reduced (control mean fluorescence intensity (MFI) = 2348, SpA MFI = 2219, RA MFI = 226; p < 0.001). MAIT cells were hyporesponsive, shown by minimal upregulation of CD25 and CD69 to E. coli stimulation (control, CD25 MFI = 177, CD69 MFI = 1307; SpA, CD25 MFI = 95, CD69 MFI = 1257; RA, CD25 MFI = 0, CD69 MFI = 467; p < 0.001 and p = 0.01 respectively).

Conclusion: In early untreated RA patients, the peripheral MAIT cell composition was altered, with reduced levels of CD161 expression, and cells were hyporesponsive to stimulation. MAIT cell dysfunction may provide a link between the microbiome and development of RA.
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http://dx.doi.org/10.1186/s13075-018-1799-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6321723PMC
January 2019

Autoantibody Development under Treatment with Immune-Checkpoint Inhibitors.

Cancer Immunol Res 2019 01 13;7(1):6-11. Epub 2018 Nov 13.

Department of Rheumatology, Leiden University Medical Center, Leiden, the Netherlands.

Immune-checkpoint inhibitors (ICIs) activate the immune system to assault cancer cells in a manner that is not antigen specific. We hypothesized that tolerance may also be broken to autoantigens, resulting in autoantibody formation, which could be associated with immune-related adverse events (irAEs) and antitumor efficacy. Twenty-three common clinical autoantibodies in pre- and posttreatment sera from 133 ipilimumab-treated melanoma patients were determined, and their development linked to the occurrence of irAEs, best overall response, and survival. Autoantibodies developed in 19.2% (19/99) of patients who were autoantibody-negative pretreatment. A nonsignificant association was observed between development of any autoantibodies and any irAEs [OR, 2.92; 95% confidence interval (CI) 0.85-10.01]. Patients with antithyroid antibodies after ipilimumab had significantly more thyroid dysfunction under subsequent anti-PD-1 therapy: 7/11 (54.6%) patients with antithyroid antibodies after ipilimumab developed thyroid dysfunction under anti-PD1 versus 7/49 (14.3%) patients without antibodies (OR, 9.96; 95% CI, 1.94-51.1). Patients who developed autoantibodies showed a trend for better survival (HR for all-cause death: 0.66; 95% CI, 0.34-1.26) and therapy response (OR, 2.64; 95% CI, 0.85-8.16). We conclude that autoantibodies develop under ipilimumab treatment and could be a potential marker of ICI toxicity and efficacy.
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http://dx.doi.org/10.1158/2326-6066.CIR-18-0245DOI Listing
January 2019

Effects of anticoagulants and storage conditions on clinical oxylipid levels in human plasma.

Biochim Biophys Acta Mol Cell Biol Lipids 2018 12 9;1863(12):1511-1522. Epub 2018 Oct 9.

Leiden University Medical Center, Center for Proteomics and Metabolomics, Albinusdreef 2, 2300RC Leiden, the Netherlands. Electronic address:

Metabolomics and lipidomics are of fundamental importance to personalized healthcare. Particularly the analysis of bioactive lipids is of relevance to a better understanding of various diseases. Within clinical routines, blood derived samples are widely used for diagnostic and research purposes. Hence, standardized and validated procedures for blood collection and storage are mandatory, in order to guarantee sample integrity and relevant study outcomes. We here investigated different plasma storage conditions and their effect on plasma fatty acid and oxylipid levels. Our data clearly indicate the importance of storage conditions for plasma lipidomic analysis. Storage at very low temperature (-80 °C) and the addition of methanol directly after sampling are the most important measures to avoid ex vivo synthesis of oxylipids. Furthermore, we identified critical analytes being affected under certain storage conditions. Finally, we carried out chiral analysis and found possible residual enzymatic activity to be one of the contributors to the ex vivo formation of oxylipids even at -20 °C.
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http://dx.doi.org/10.1016/j.bbalip.2018.10.003DOI Listing
December 2018

Sequential Prodrug Strategy To Target and Eliminate ACPA-Selective Autoreactive B Cells.

Mol Pharm 2018 12 26;15(12):5565-5573. Epub 2018 Oct 26.

Department of Biomolecular Chemistry, Institute for Molecules and Materials , Radboud University Nijmegen 6525 AJ , The Netherlands.

Autoreactive B cells are thought to play a pivotal role in many autoimmune diseases. Rheumatoid arthritis (RA) is an autoimmune disease affecting ∼1% of the Western population and is hallmarked by the presence of anticitrullinated proteins antibodies (ACPA) produced by autoreactive B cells. We intend to develop a method to target and selectively eliminate these autoreactive B cells using a sequential antigen prodrug targeting strategy. As ACPA-expressing B cells are thought to play essential roles in RA-disease pathogenesis, we used this B cell response as a prototype to analyze the feasibility to generate a construct consisting of a biologically silenced, that is, blocked, antigen connected to a cytotoxic prodrug. Blocking of the antigen is considered relevant as it is anticipated that circulating autoantibodies will otherwise clear the antigen-prodrug before it can reach the target cell. The antigen-prodrug can only bind to the autoantigen-specific B cell receptor (BCR) upon enzymatic removal of the blocking group in close proximity of the B cell surface. BCR binding ultimately induces antigen-specific cytotoxicity after internalization of the antigen. We have synthesized a cyclic citrullinated peptide (CCP) antigen suitable for BCR binding and demonstrated that binding by ACPA was impaired upon introduction of a carboxy- p-nitrobenzyl (CNBz) blocking group at the side chain of the citrulline residue. Enzymatic removal of the CNBz moiety by nitroreductase fully restored citrulline-specific recognition by both ACPA and ACPA-expressing B cells and showed targeted cell death of CCP-recognizing B cells only. These results mark an important step toward antigen-specific B cell targeting in general and more specifically in RA, as successful blocking and activation of citrullinated antigens forms the basis for subsequent use of such construct as a prodrug in the context of autoimmune diseases.
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http://dx.doi.org/10.1021/acs.molpharmaceut.8b00741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6282105PMC
December 2018

Generation and Characterization of Anti-Citrullinated Protein Antibody-Producing B Cell Clones From Rheumatoid Arthritis Patients.

Arthritis Rheumatol 2019 03 2;71(3):340-350. Epub 2019 Feb 2.

Academic Medical Center, University of Amsterdam, and UCB Pharma, Brussels, Belgium.

Objective: Anti-citrullinated protein antibodies (ACPAs) are a hallmark of rheumatoid arthritis (RA). Aside from autoantibody production, the function of autoantigen-specific B cells remains poorly understood in the context of this disease. This study set out to elucidate autoantigen-specific B cell functions through the isolation and immortalization of unique citrullinated protein/peptide (CP)-reactive B cell clones from RA patients.

Methods: B cell clones from either the blood or synovial fluid of cyclic citrullinated peptide 2 (CCP2) antibody-positive RA patients were immortalized by genetic reprogramming with Bcl-6 and Bcl-xL. Enzyme-linked immunosorbent assay and flow cytometry were used to identify CCP2-reactive clones and to further characterize surface marker and cytokine expression as well as B cell receptor signaling competence. Global gene expression profiles were interrogated by RNA sequencing.

Results: Three unique CP-reactive memory B cell clones were generated from the blood or synovial fluid of 2 RA patients. CP-reactive memory B cells did not appear to be broadly cross-reactive, but rather had a fairly restricted epitope recognition profile. These clones were able to secrete both pro- and antiinflammatory cytokines and had a unique surface profile of costimulatory molecules and receptors, including CD40 and C5a receptor type 1, when compared to non-CP-reactive clones from the same patient. In addition, CP-reactive clones bound citrullinated protein, but not native protein, and could mobilize calcium in response to antigen binding.

Conclusion: CP-reactive memory B cells comprise a rare, seemingly oligoclonal population with restricted epitope specificity and distinct phenotypic and molecular characteristics suggestive of antigen-presenting cells. Cloning by genetic reprogramming opens new avenues to study the function of autoreactive memory B cells, especially in terms of antigen processing, presentation, and subsequent T cell polarization.
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http://dx.doi.org/10.1002/art.40739DOI Listing
March 2019

Structural Basis of Cross-Reactivity of Anti-Citrullinated Protein Antibodies.

Arthritis Rheumatol 2019 02 4;71(2):210-221. Epub 2019 Jan 4.

Karolinska Institutet, Stockholm, Sweden, and Southern Medical University, Guangzhou, China.

Objective: Anti-citrullinated protein antibodies (ACPAs) develop many years before the clinical onset of rheumatoid arthritis (RA). This study was undertaken to address the molecular basis of the specificity and cross-reactivity of ACPAs from patients with RA.

Methods: Antibodies isolated from RA patients were expressed as monoclonal chimeric antibodies with mouse Fc. These antibodies were characterized for glycosylation using mass spectrometry, and their cross-reactivity was assessed using Biacore and Luminex immunoassays. The crystal structures of the antigen-binding fragment (Fab) of the monoclonal ACPA E4 in complex with 3 different citrullinated peptides were determined using x-ray crystallography. The prevalence of autoantibodies reactive against 3 of the citrullinated peptides that also interacted with E4 was investigated by Luminex immunoassay in 2 Swedish cohorts of RA patients.

Results: Analysis of the crystal structures of a monoclonal ACPA from human RA serum in complex with citrullinated peptides revealed key residues of several complementarity-determining regions that recognized the citrulline as well as the neighboring peptide backbone, but with limited contact with the side chains of the peptides. The same citrullinated peptides were recognized by high titers of serum autoantibodies in 2 large cohorts of RA patients.

Conclusion: These data show, for the first time, how ACPAs derived from human RA serum recognize citrulline. The specific citrulline recognition and backbone-mediated interactions provide a structural explanation for the promiscuous recognition of citrullinated peptides by RA-specific ACPAs.
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http://dx.doi.org/10.1002/art.40698DOI Listing
February 2019

Mast cells in early rheumatoid arthritis associate with disease severity and support B cell autoantibody production.

Ann Rheum Dis 2018 12 20;77(12):1773-1781. Epub 2018 Aug 20.

Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.

Objectives: Mast cells (MCs) are involved in the pathogenesis of rheumatoid arthritis (RA). However, their contribution remains controversial. To establish their role in RA, we analysed their presence in the synovium of treatment-naïve patients with early RA and their association and functional relationship with histological features of synovitis.

Methods: Synovial tissue was obtained by ultrasound-guided biopsy from treatment-naïve patients with early RA (n=99). Immune cells (CD3/CD20/CD138/CD68) and their relationship with CD117MCs in synovial tissue were analysed by immunohistochemistry (IHC) and immunofluorescence (IF). The functional involvement of MCs in ectopic lymphoid structures (ELS) was investigated , by coculturing MCs with naïve B cells and anticitrullinated protein antibodies (ACPA)-producing B cell clones, and in interleukin-27 receptor alpha (IL27)-deficient and control mice during antigen-induced arthritis (AIA).

Results: High synovial MC counts are associated with local and systemic inflammation, autoantibody positivity and high disease activity. IHC/IF showed that MCs reside at the outer border of lymphoid aggregates. Furthermore, human MCs promote the activation and differentiation of naïve B cells and induce the production of ACPA, mainly via contact-dependent interactions. In AIA, synovial MC numbers increase in IL27 deficient mice, in association with ELS and worse disease activity.

Conclusions: Synovial MCs identify early RA patients with a severe clinical form of synovitis characterised by the presence of ELS.
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http://dx.doi.org/10.1136/annrheumdis-2018-213418DOI Listing
December 2018

Secretory form of rheumatoid arthritis-associated autoantibodies in serum are mainly of the IgM isotype, suggesting a continuous reactivation of autoantibody responses at mucosal surfaces.

Ann Rheum Dis 2019 01 14;78(1):146-148. Epub 2018 Aug 14.

Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, The Netherlands.

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http://dx.doi.org/10.1136/annrheumdis-2018-213724DOI Listing
January 2019

The anti-carbamylated protein antibody response is of overall low avidity despite extensive isotype switching.

Rheumatology (Oxford) 2018 09;57(9):1583-1591

Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.

Objective: To better understand the contribution of autoantibodies in RA and the biology of their responses, we evaluated the avidity of the anti-carbamylated protein (anti-CarP) antibody response.

Methods: The avidity of anti-CarP antibody, ACPA and anti-tetanus toxoid IgG were determined using elution assays. Anti-CarP IgG avidity was measured in sera of 107 RA patients, 15 paired SF and serum samples and 8 serially sampled sera before and after disease onset.

Results: The avidity of anti-CarP IgG is low compared with the avidity of anti-tetanus toxoid IgG present in the same sera. Likewise, although less pronounced, anti-CarP also displayed a lower avidity as compared with the avidity of ACPA IgG. No difference in anti-CarP IgG avidity is observed between ACPA positive or ACPA negative patients. Anti-CarP IgG avidity is higher in anti-CarP IgM-negative compared with IgM-positive individuals. Furthermore, the anti-CarP avidity in serum is higher than in SF. Using samples of individuals that over time developed RA we observed no anti-CarP avidity maturation in the years before disease onset. In contrast to ACPA avidity, the anti-CarP avidity is not associated with severity of joint destruction.

Conclusion: The anti-CarP response is of overall low avidity, even lower than the ACPA IgG avidity, and does not show apparent avidity maturation before or around disease onset. Overall, isotype switch and avidity maturation seem to be uncoupled as isotype switch occurs without avidity maturation, pointing towards a commonality in the regulation of both autoantibody responses as opposed to the pathways governing recall responses.
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http://dx.doi.org/10.1093/rheumatology/key135DOI Listing
September 2018

Triple Positivity for Anti-Citrullinated Protein Autoantibodies, Rheumatoid Factor, and Anti-Carbamylated Protein Antibodies Conferring High Specificity for Rheumatoid Arthritis: Implications for Very Early Identification of At-Risk Individuals.

Arthritis Rheumatol 2018 11 16;70(11):1721-1731. Epub 2018 Sep 16.

Leiden University Medical Center, Leiden, The Netherlands.

Objective: In rheumatoid arthritis (RA), anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) are commonly used to aid in the diagnosis. Although these autoantibodies are mainly found in RA, their specificity is not optimal. It is therefore difficult to identify RA patients, especially in very early disease, based on the presence of ACPAs and RF alone. In addition, anti-carbamylated protein (anti-CarP) antibodies have diagnostic and prognostic value, since their presence is associated with joint damage in RA patients and also associated with the future development of RA in patients with arthralgia. Therefore, the aim of the present study was to investigate the value of combined antibody testing in relation to prediction and diagnosis of (early) RA.

Methods: A literature search resulted in identification of 12 relevant studies, consisting of RA patients, pre-RA individuals, disease controls, healthy first-degree relatives of RA patients, and healthy control subjects, in which data on RF, ACPAs, and anti-CarP antibody status were available. Using these data, random effects meta-analyses were carried out for several antibody combinations.

Results: The individual antibodies were highly prevalent in patients with RA (34-80%) compared to the control groups, but were also present in non-RA controls (0-23%). For the classification of most subjects correctly as having RA or as a non-RA control, the combination of ACPAs and/or RF often performed well (specificity 65-100%, sensitivity 59-88%). However, triple positivity for ACPAs, RF, and anti-CarP antibodies resulted in a higher specificity for RA (98-100%), accompanied by a lower sensitivity (11-39%).

Conclusion: As the rheumatology field is moving toward very early identification of RA and possible screening for individuals at maximum risk of RA in populations with a low pretest probability, an autoantibody profile of triple positivity for ACPAs, RF, and anti-CarP provides interesting information that might help identify individuals at risk of developing RA.
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http://dx.doi.org/10.1002/art.40562DOI Listing
November 2018

Low amounts of bisecting glycans characterize cerebrospinal fluid-borne IgG.

J Neuroimmunol 2018 07 16;320:19-24. Epub 2018 Apr 16.

Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Department of Internal Medicine 3, Rheumatology and Immunology, Universitätsklinikum Erlangen, Erlangen, Germany. Electronic address:

Immunoglobulin G (IgG) harbors a conserved N-glycosylation site which is important for its effector functions. Changes in glycosylation of IgG occur in many autoimmune diseases but also in physiological conditions. Therefore, the glycosylation pattern of serum IgG is well characterized. However, limited data is available on the glycosylation pattern of IgG in cerebrospinal fluid (CSF) compared to serum. Here, we report significantly reduced levels of bisected glycans in CSF IgG. Galactosylation and sialylation of IgG4 also differed significantly. Therefore, we propose a common mechanism mediating glycosylation changes of IgG at the transition from serum to CSF in steady state conditions.
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http://dx.doi.org/10.1016/j.jneuroim.2018.04.010DOI Listing
July 2018