High microRNA-145 plasma levels are associated with decreased risk of future incident venous thromboembolism: the HUNT study.

ABSTRACT: MicroRNA-145 (miR-145) has been reported to downregulate the expression of tissue factor and factor XI in vitro and decrease venous thrombus formation in animal models. However, the association between miR-145 and risk of future venous thromboembolism (VTE) in the general population remains unknown. We investigated the association between plasma levels of miR-145 and risk of future VTE in a case-cohort study. Incident VTE cases (n = 510) and a subcohort (n = 1890) were derived from the third survey of the Trøndelag Health Study (HUNT3), a population-based cohort. The expression levels of miR-145 were measured in plasma samples obtained at baseline. The study population was divided into quartiles based on miR-145 levels in participants in the subcohort, and weighted Cox regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs). Plasma levels of miR-145 were inversely associated with VTE risk. Participants with miR-145 levels in the highest quartile had a 49% lower risk of VTE (HR, 0.51; 95% CI, 0.38-0.68) than those with miR-145 in the lowest quartile in age- and sex-adjusted analysis, and the inverse association was most pronounced for unprovoked VTE (HR, 0.39; 95% CI, 0.25-0.61). Risk estimates remained virtually the same after further adjustment for body mass index, and cancer and arterial cardiovascular disease at baseline. In conclusion, elevated expression levels of miR-145 in plasma were associated with decreased risk of future incident VTE. The protective role of miR-145 against VTE is consistent with previous experimental data and suggests that miR-145 has the potential to be a target for VTE prevention.

C1 inhibitor deficiency enhances contact pathway-mediated activation of coagulation and venous thrombosis.

C1 inhibitor (C1INH) is a multifunctional serine protease inhibitor that functions as a major negative regulator of several biological pathways, including the contact pathway of blood coagulation. In humans, congenital C1INH deficiency results in a rare episodic bradykinin-mediated swelling disorder called hereditary angioedema (HAE). Patients with C1INH deficiency-associated HAE (C1INH-HAE) have increased circulating markers of activation of coagulation. Furthermore, we recently reported that patients with C1INH-HAE had a moderate but significant increased risk of venous thromboembolism. To further investigate the impact of C1INH deficiency on activation of coagulation and thrombosis, we conducted studies using patient samples and mouse models. Plasmas from patients with C1INH-HAE had significantly increased contact pathway-mediated thrombin generation. C1INH-deficient mice, which have been used as a model of C1INH-HAE, had significantly increased baseline circulating levels of prothrombin fragment 1+2 and thrombin-antithrombin complexes. In addition, whole blood from C1INH-deficient mice supported significantly increased contact pathway-mediated thrombin generation. Importantly, C1INH-deficient mice exhibited significantly enhanced venous, but not arterial, thrombus formation. Furthermore, purified human C1INH normalized contact pathway-mediated thrombin generation and venous thrombosis in C1INH-deficient mice. These findings highlight a key role for endogenous C1INH as a negative regulator of contact pathway-mediated coagulation in humans and mice. Further, this work identifies endogenous C1INH as an important negative regulator of venous thrombus formation in mice, complementing the phenotype associated with C1INH-HAE.

Optimized workflow to modify microRNA expression in primary human intravascular cells.

BACKGROUND: A comprehensive dissection of the role of microRNAs (miRNAs) in gene regulation and subsequent cell functions requires a specific and efficient knockdown or overexpression of the miRNA of interest; these are achieved by transfecting the cell of interest with a miRNA inhibitor or a miRNA mimic, respectively. Inhibitors and mimics of miRNAs with a unique chemistry and/or structural modifications are available commercially and require different transfection conditions. Here, we aimed to investigate how various conditions affect the transfection efficacy of two miRNAs with high and low endogenous expression, miR-15a-5p and miR-20b-5p respectively, in human primary cells. RESULTS: MiRNA inhibitors and mimics from two commonly used commercial vendors were employed, i.e., mirVana (Thermo Fisher Scientific) and locked nucleic acid (LNA) miRNA (Qiagen). We systematically examined and optimized the transfection conditions of such miRNA inhibitors and mimics to primary endothelial cells and monocytes using either a lipid-based carrier (lipofectamine) for delivery or an unassisted uptake. Transfection of LNA inhibitors with either phosphodiester (PE)- or phosphorothioate (PS)-modified nucleotide bonds, delivered using a lipid-based carrier, efficiently downregulated the expression levels of miR-15a-5p already 24 h following transfection. MirVana miR-15a-5p inhibitor displayed a less efficient inhibitory effect, which was not improved 48 h following a single transfection or two consecutive transfections. Interestingly, LNA-PS miR-15a-5p inhibitor efficiently reduced the levels of miR-15a-5p when delivered without a lipid-based carrier in both ECs and monocytes. When using a carrier, mirVana and LNA miR-15a-5p and miR-20b-5p mimics showed similar efficiency 48 h following transfection to ECs and monocytes. None of the miRNA mimics effectively induced overexpression of the respective miRNA when given to primary cells without a carrier. CONCLUSION: LNA miRNA inhibitors efficiently downregulated the cellular expression of miRNA, such as miR-15a-5p. Furthermore, our findings suggest that LNA-PS miRNA inhibitors can be delivered in the absence of a lipid-based carrier, whereas miRNA mimics need the aid of a lipid-based carrier to achieve sufficient cellular uptake.

Complement factors B, D, C3bBbP and risk of future venous thromboembolism.

The complement system appears to be involved in the pathogenesis of venous thromboembolism (VTE). We investigated the association of complement factors (CF) B, D, and the alternative pathway convertase, C3bBbP, measured at inclusion, with the risk of future VTE in a nested case-control study; 380 VTE patients and 804 age- and sex-matched controls derived from the Tromsø study. Odds ratios (ORs) with 95% confidence intervals (95% CI) for VTE across tertiles of CF concentrations were estimated using logistic regression. There was no association between CFB or CFD and risk of future VTE. Higher levels of C3bBbP gave an increased risk of provoked VTE; subjects in Q4 had a 1.68-fold higher OR compared with Q1 in the age-, sex- and BMI-adjusted model (OR 1.68; 95% CI 1.08-2.64). There was no increased risk of future VTE in individuals with higher levels of complement factors B or D of the alternative pathway. Increased levels of the alternative pathway activation product, C3bBbP, showed an association with future risk of provoked VTE.

Elevated plasma concentration of complement factor C5 is associated with risk of future venous thromboembolism.

The role of complement in the pathogenesis of venous thromboembolism (VTE) is unclear. We wanted to investigate (1) whether plasma complement component C5 (C5) levels are influenced by genetic variants or chronic inflammation and (2) the association between plasma C5 and risk of future VTE in a nested case-control study of 415 patients with VTE and 848 age- and sex-matched controls derived from the Tromsø Study. Plasma C5 levels were measured at inclusion. Odds ratios (ORs) with 95% confidence intervals (95% CIs) for provoked and unprovoked VTE across tertiles of C5 concentrations were estimated by logistic regression. Adjustment for C-reactive protein (CRP) served as a proxy for general inflammation. Whole-exome sequencing and protein quantitative trait loci analyses were performed to assess genetic influence on C5 concentrations. There was no association between genome-wide or C5-related gene variants and C5 levels. The association between plasma C5 levels and VTE risk displayed a threshold effect, where subjects with C5 levels above the lowest tertile had increased risk of VTE. Subjects in tertile 3 (highest C5 levels) had an age- and sex-adjusted OR of 1.45 (95% CI, 1.07-1.96) compared with tertile 1 (lowest). These statistics were more pronounced for unprovoked VTE (OR, 1.70; 95% CI, 1.11-2.60). Adjustments for body mass index and CRP had minor impact on risk estimates. The OR increased substantially with shorter time between blood sampling and VTE event. In conclusion, plasma C5 was associated with risk of future VTE. C5 levels were not genetically regulated and were only slightly influenced by chronic inflammation.

High Levels of Complement Activating Enzyme MASP-2 Are Associated With the Risk of Future Incident Venous Thromboembolism.

BACKGROUND: Experimental studies have shown that the complement activating enzyme MASP-2 (mannose-binding lectin associated serine protease 2) exhibits a thrombin-like activity and that inhibition of MASP-2 protects against thrombosis. In this study, we investigated whether plasma MASP-2 levels were associated with risk of future venous thromboembolism (VTE) and whether genetic variants linked to MASP-2 levels were associated with VTE risk. METHODS: We conducted a population-based nested case-control study involving 410 VTE patients and 842 age- and sex-matched controls derived from the Norwegian Tromsø Study. Logistic regression was used to estimate odds ratios (ORs) of VTE across MASP-2 quartiles. Whole-exome sequencing and protein quantitative trait loci analyses were performed to assess genetic variants associated with MASP-2 levels. A 2-sample Mendelian randomization study, also including data from the INVENT consortium (International Network of Venous Thrombosis), was performed to assess causality. RESULTS: Subjects with plasma MASP-2 in the highest quartile had a 48% higher OR of VTE (OR, 1.48 [95% CI, 1.06-2.06]) and 83% higher OR of deep vein thrombosis (OR, 1.83 [95% CI, 1.23-2.73]) compared with those with MASP-2 levels in the lowest quartile. The protein quantitative trait loci analysis revealed that 3 previously described gene variants, rs12711521 (minor allele frequency, 0.153), rs72550870 (minor allele frequency, 0.045; missense variants in the MASP2 gene), and rs2275527 (minor allele frequency, 0.220; exon variant in the adjacent MTOR gene) explained 39% of the variation of MASP-2 plasma concentration. The OR of VTE per 1 SD increase in genetically predicted MASP-2 was 1.03 ([95% CI, 1.01-1.05] P=0.0011). CONCLUSIONS: Our findings suggest that high plasma MASP-2 levels are causally associated with risk of future VTE.

Polymorphisms in human immunoglobulin heavy chain variable genes and their upstream regions.

Germline variations in immunoglobulin genes influence the repertoire of B cell receptors and antibodies, and such polymorphisms may impact disease susceptibility. However, the knowledge of the genomic variation of the immunoglobulin loci is scarce. Here, we report 25 potential novel germline IGHV alleles as inferred from rearranged naïve B cell cDNA repertoires of 98 individuals. Thirteen novel alleles were selected for validation, out of which ten were successfully confirmed by targeted amplification and Sanger sequencing of non-B cell DNA. Moreover, we detected a high degree of variability upstream of the V-REGION in the 5'UTR, L-PART1 and L-PART2 sequences, and found that identical V-REGION alleles can differ in upstream sequences. Thus, we have identified a large genetic variation not only in the V-REGION but also in the upstream sequences of IGHV genes. Our findings provide a new perspective for annotating immunoglobulin repertoire sequencing data.

Plasma Cells Are the Most Abundant Gluten Peptide MHC-expressing Cells in Inflamed Intestinal Tissues From Patients With Celiac Disease.

BACKGROUND & AIMS: Development of celiac disease is believed to involve the transglutaminase-dependent response of CD4+ T cells toward deamidated gluten peptides in the intestinal mucosa of individuals with specific HLA-DQ haplotypes. We investigated the antigen presentation process during this mucosal immune response. METHODS: We generated monoclonal antibodies (mAbs) specific for the peptide-MHC (pMHC) complex of HLA-DQ2.5 and the immunodominant gluten epitope DQ2.5-glia-α1a using phage display. We used these mAbs to assess gluten peptide presentation and phenotypes of presenting cells by flow cytometry and enzyme-linked immune absorbent spot (ELISPOT) in freshly prepared single-cell suspensions from intestinal biopsies from 40 patients with celiac disease (35 untreated and 5 on a gluten-free diet) as well as 18 subjects with confirmed noninflamed gut mucosa (controls, 12 presumed healthy, 5 undergoing pancreatoduodenectomy, and 1 with potential celiac disease). RESULTS: Using the mAbs, we detected MHC complexes on cells from intestinal biopsies from patients with celiac disease who consume gluten, but not from patients on gluten-free diets. We found B cells and plasma cells to be the most abundant cells that present DQ2.5-glia-α1a in the inflamed mucosa. We identified a subset of plasma cells that expresses B-cell receptors (BCR) specific for gluten peptides or the autoantigen transglutaminase 2 (TG2). Expression of MHC class II (MHCII) was not restricted to these specific plasma cells in patients with celiac disease but was observed in an average 30% of gut plasma cells from patients and controls. CONCLUSIONS: A population of plasma cells from intestinal biopsies of patients with celiac disease express MHCII; this is the most abundant cell type presenting the immunodominant gluten peptide DQ2.5-glia-α1a in the tissues from these patients. These results indicate that plasma cells in the gut can function as antigen-presenting cells and might promote and maintain intestinal inflammation in patients with celiac disease or other inflammatory disorders.

High-Throughput Single-Cell Analysis of B Cell Receptor Usage among Autoantigen-Specific Plasma Cells in Celiac Disease.

Characterization of Ag-specific BCR repertoires is essential for understanding disease mechanisms involving humoral immunity. This is optimally done by interrogation of paired H chain V region (VH) and L chain V region (VL) sequences of individual and Ag-specific B cells. By applying single-cell high-throughput sequencing on gut lesion plasma cells (PCs), we have analyzed the transglutaminase 2 (TG2)-specific VH:VL autoantibody repertoire of celiac disease (CD) patients. Autoantibodies against TG2 are a hallmark of CD, and anti-TG2 IgA-producing gut PCs accumulate in patients upon gluten ingestion. Altogether, we analyzed paired VH and VL sequences of 1482 TG2-specific and 1421 non-TG2-specific gut PCs from 10 CD patients. Among TG2-specific PCs, we observed a striking bias in IGHV and IGKV/IGLV gene usage, as well as pairing preferences with a particular presence of the IGHV5-51:IGKV1-5 pair. Selective and biased VH:VL pairing was particularly evident among expanded clones. In general, TG2-specific PCs had lower numbers of mutations both in VH and VL genes than in non-TG2-specific PCs. TG2-specific PCs using IGHV5-51 had particularly few mutations. Importantly, VL segments paired with IGHV5-51 displayed proportionally low mutation numbers, suggesting that the low mutation rate among IGHV5-51 PCs is dictated by the BCR specificity. Finally, we observed selective amino acid changes in VH and VL and striking CDR3 length and J segment selection among TG2-specific IGHV5-51:IGKV1-5 pairs. Hence this study reveals features of a disease- and Ag-specific autoantibody repertoire with preferred VH:VL usage and pairings, limited mutations, clonal dominance, and selection of particular CDR3 sequences.

Analysis of celiac disease autoreactive gut plasma cells and their corresponding memory compartment in peripheral blood using high-throughput sequencing.

Autoreactive IgA plasma cells (PCs) specific for the enzyme transglutaminase 2 (TG2) are abundant in the small intestine of patients with active celiac disease (CD), and their number drops in patients treated by dietary gluten elimination. Little is known about their characteristics and their role in the disease. In this study, using high-throughput sequencing of the IgH V region (IGHV) genes, we have studied features of TG2-specific PCs and their related B cell clones in peripheral blood. We found that TG2-specific PCs from both untreated and treated patients have acquired lower number of somatic hypermutation and used focused IGHV repertoire with overrepresentation of the IGHV3-48, IGHV4-59, IGHV5-10-1, and IGHV5-51 gene segments. Furthermore, these PCs were clonally expanded and showed signs of affinity maturation. Lineage trees demonstrated shared clones between gut PCs and blood memory B cells, primarily IgAs. Some trees also involved IgG cells, suggesting that anti-TG2 IgA and IgG responses are related. Similarly to TG2-specific PCs, clonally related memory IgA B cells of blood showed lower mutation rates with biased usage of IGHV3-48 and IGHV5-51. Such memory cells were rare in peripheral blood, yet detectable in most patients assessed by production of anti-TG2 Abs in vitro following stimulation of cells from patients who had been on a long-term gluten-free diet. Thus, the Ab response to TG2 in CD, while maintaining its IGHV gene usage, is dynamically regulated in response to gluten exposure with a low degree of maintenance at both PC and memory B cell levels in patients in remission.

Coeliac disease - from genetic and immunological studies to clinical applications.

Coeliac disease is a common and important gastrointestinal disease. It affects at least 1%, most Western European populations and in Nordic countries it is even more frequent. It is strongly associated with certain Human Leukocyte Antigen-DQ genes and triggered by ingestion of wheat gluten and related cereals from rye and barley. The diagnosis relies on a combination of clinical signs, serology and small intestinal biopsy. Work during the last couple of decades has shown that gluten-specific, Human Leukocyte Antigen-DQ-restricted T-cells in the intestinal mucosa are of paramount importance in the disease process. The gluten peptides are chemically modified by the endogenous enzyme transglutaminase 2, the same enzyme that serves as target in today's sensitive serological tests for coeliac disease. The increasing knowledge on the disease process allows for development of improved diagnosis, patient care and new treatment modalities.

Small bowel, celiac disease and adaptive immunity.

BACKGROUND: Celiac disease is a multifactorial and polygenic disease with autoimmune features. The disease is caused by an inappropriate immune response to gluten. Elimination of gluten from the diet leads to disease remission, which is the basis for today's treatment of the disease. There is an unmet need for new alternative treatments. KEY MESSAGES: Genetic findings point to adaptive immunity playing a key role in the pathogenesis of celiac disease. MHC is by far the single most important genetic factor in the disease. In addition, a number of non-MHC genes, the majority of which have functions related to T cells and B cells, also contribute to the genetic predisposition, but each of them has modest effect. The primary MHC association is with HLA-DQ2 and HLA-DQ8. These HLA molecules present gluten epitopes to CD4+ T cells which can be considered to be the master regulators of the immune reactions that lead to the disease. The epitopes which the T cells recognize are usually deamidated, and this deamidation is mediated by the enzyme transglutaminase 2 (TG2). Celiac disease patients have disease-specific antibodies. In addition to antibodies to gluten, these include autoantibodies to TG2. Antibodies to deamidated gluten are nearly as specific for celiac disease as the anti-TG2 antibodies. Both types of antibodies appear only to be produced in subjects who are HLA-DQ2 or HLA-DQ8 when they are consuming gluten. CONCLUSION: It is hardly coincidental that TG2 is implicated in T-cell epitope formation and at the same time a target for autoantibodies. Understanding this connection is one of the major challenges for obtaining a complete understanding of how gluten causes tissue destruction and remodeling of the mucosa in the small bowel.

Identification of extracellular vesicles from their Raman spectra via self-supervised learning.

Extracellular vesicles (EVs) released from cells attract interest for their possible role in health and diseases. The detection and characterization of EVs is challenging due to the lack of specialized methodologies. Raman spectroscopy, however, has been suggested as a novel approach for biochemical analysis of EVs. To extract information from the spectra, a novel deep learning architecture is explored as a versatile variant of autoencoders. The proposed architecture considers the frequency range separately from the intensity of the spectra. This enables the model to adapt to the frequency range, rather than requiring that all spectra be pre-processed to the same frequency range as it was trained on. It is demonstrated that the proposed architecture accepts Raman spectra of EVs and lipoproteins from 13 biological sources and from two laboratories. High reconstruction accuracy is maintained despite large variances in frequency range and noise level. It is also shown that the architecture is able to cluster the biological nanoparticles by their Raman spectra and differentiate them by their origin without pre-processing of the spectra or supervision during learning. The model performs label-free differentiation, including separating EVs from activated vs. non-activated blood platelets and EVs/lipoproteins from prostate cancer patients versus non-cancer controls. The differentiation is evaluated by creating a neural network classifier that observes the features extracted by the model to classify the spectra according to their sample origin. The classification reveals a test sensitivity of 92.2 % and selectivity of 92.3 % over 769 measurements from two labs that have different measurement configurations.

Extracellular vesicles from activated platelets possess a phospholipid-rich biomolecular profile and enhance prothrombinase activity.

BACKGROUND: Extracellular vesicles (EVs), in particular those derived from activated platelets, are associated with a risk of future venous thromboembolism. OBJECTIVES: To study the biomolecular profile and function characteristics of EVs from control (unstimulated) and activated platelets. METHODS: Biomolecular profiling of single or very few (1-4) platelet-EVs (control/stimulated) was performed by Raman tweezers microspectroscopy. The effects of such EVs on the coagulation system were comprehensively studied. RESULTS: Raman tweezers microspectroscopy of platelet-EVs followed by biomolecular component analysis revealed for the first time 3 subsets of EVs: (i) protein rich, (ii) protein/lipid rich, and (iii) lipid rich. EVs from control platelets presented a heterogeneous biomolecular profile, with protein-rich EVs being the main subset (58.7% ± 3.5%). Notably, the protein-rich subset may contain a minor contribution from other extracellular particles, including protein aggregates. In contrast, EVs from activated platelets were more homogeneous, dominated by the protein/lipid-rich subset (>85%), and enriched in phospholipids. Functionally, EVs from activated platelets increased thrombin generation by 52.4% and shortened plasma coagulation time by 34.6% ± 10.0% compared with 18.6% ± 13.9% mediated by EVs from control platelets (P = .015). The increased procoagulant activity was predominantly mediated by phosphatidylserine. Detailed investigation showed that EVs from activated platelets increased the activity of the prothrombinase complex (factor Va:FXa:FII) by more than 6-fold. CONCLUSION: Our study reports a novel quantitative biomolecular characterization of platelet-EVs possessing a homogenous and phospholipid-enriched profile in response to platelet activation. Such characteristics are accompanied with an increased phosphatidylserine-dependent procoagulant activity. Further investigation of a possible role of platelet-EVs in the pathogenesis of venous thromboembolism is warranted.

Comparison of assays measuring extracellular vesicle-tissue factor in plasma samples: Communication from the ISTH SSC Subcommittee on Vascular Biology.

BACKGROUND: Scientific and clinical interest in extracellular vesicles (EVs) is growing. EVs that expose tissue factor (TF) bind factor VII/VIIa and can trigger coagulation. Highly procoagulant TF-exposing EVs are detectable in the circulation in various diseases, such as sepsis, COVID-19 or cancer. Many in-house and commercially available assays have been developed to measure EV-TF activity and antigen but only a few studies have compared some of these assays. The ISTH SSC Subcommittee on Vascular Biology initiated a multicenter study to compare the sensitivity, specificity and reproducibility of these assays. MATERIALS AND METHODS: Platelet-depleted plasma samples were prepared from blood of healthy donors. The plasma samples were spiked either with EVs from human milk, or EVs from TF-positive and TF-negative cell lines. Plasma was also prepared from whole human blood with or without LPS stimulation. Twenty-one laboratories measured EV-TF activity and antigen in the prepared samples using their own assays representing 18 functional and 9 antigenic assays. RESULTS: There was a large variability in the absolute values for the different EV-TF activity and antigen assays. Activity assays had higher specificity and sensitivity compared to antigen assays. In addition, there was a large intra-assay and inter-assay variability. Functional assays that used a blocking anti-TF antibody or immunocapture were the most specific and sensitive. Activity assays that used immunocapture had a lower coefficient of variation compared to assays that isolated EVs by high-speed centrifugation. CONCLUSION: Based on this multicenter study, we recommend measuring EV-TF using a functional assay in the presence of an anti-TF antibody.

Implementation of the CDC translational informatics platform--from genetic variants to the national Swedish Rheumatology Quality Register.

BACKGROUND: Sequencing of the human genome and the subsequent analyses have produced immense volumes of data. The technological advances have opened new windows into genomics beyond the DNA sequence. In parallel, clinical practice generate large amounts of data. This represents an underused data source that has much greater potential in translational research than is currently realized. This research aims at implementing a translational medicine informatics platform to integrate clinical data (disease diagnosis, diseases activity and treatment) of Rheumatoid Arthritis (RA) patients from Karolinska University Hospital and their research database (biobanks, genotype variants and serology) at the Center for Molecular Medicine, Karolinska Institutet. METHODS: Requirements engineering methods were utilized to identify user requirements. Unified Modeling Language and data modeling methods were used to model the universe of discourse and data sources. Oracle11g were used as the database management system, and the clinical development center (CDC) was used as the application interface. Patient data were anonymized, and we employed authorization and security methods to protect the system. RESULTS: We developed a user requirement matrix, which provided a framework for evaluating three translation informatics systems. The implementation of the CDC successfully integrated biological research database (15172 DNA, serum and synovial samples, 1436 cell samples and 65 SNPs per patient) and clinical database (5652 clinical visit) for the cohort of 379 patients presents three profiles. Basic functionalities provided by the translational medicine platform are research data management, development of bioinformatics workflow and analysis, sub-cohort selection, and re-use of clinical data in research settings. Finally, the system allowed researchers to extract subsets of attributes from cohorts according to specific biological, clinical, or statistical features. CONCLUSIONS: Research and clinical database integration is a real challenge and a road-block in translational research. Through this research we addressed the challenges and demonstrated the usefulness of CDC. We adhered to ethical regulations pertaining to patient data, and we determined that the existing software solutions cannot meet the translational research needs at hand. We used RA as a test case since we have ample data on active and longitudinal cohort.

Multifunctional T cell reactivity with native and glycosylated type II collagen in rheumatoid arthritis.

OBJECTIVE: Type II collagen (CII) is a cartilage-specific protein to which a loss of immune tolerance may trigger autoimmune reactions and cause arthritis. The major T cell epitope on CII, amino acids 259-273, can be presented by several HLA-DRB1 04 alleles in its native or posttranslational glycosylated form. The present study was undertaken to functionally explore and compare CII-autoreactive T cells from blood and synovial fluid of patients with rheumatoid arthritis (RA). METHODS: Peripheral blood was obtained from HLA-DRB1 04-positive RA patients (n = 10) and control subjects (n = 10) and stimulated in vitro with several variants of the CII(259-273) epitope, i.e., unmodified, glycosylated on Lys-264, glycosylated on Lys-270, or glycosylated on both Lys-264 and Lys-270. Up-regulation of CD154 was used to identify responding T cells. These cells were further characterized by intracellular staining for interleukin-17 (IL-17), interferon-γ (IFNγ), and IL-2 by flow cytometry. Synovial T cells from RA patients were investigated in parallel. RESULTS: Multifunctional T cell responses toward all examined variants of the CII(259-273) peptide could be detected in RA patients and, to a lesser extent, also in healthy HLA-matched controls (P < 0.001). In RA patients, a comparison between blood- and joint-derived T cell function revealed a significant increase in levels of the proinflammatory cytokine IFNγ in synovial T cells (P = 0.027). Studies of longitudinally obtained samples showed that T cell responses were sustained over the course of disease, and even included epitope spreading. CONCLUSION: The identification of inflammatory T cell responses to both glycosylated and nonglycosylated variants of the major CII epitope in RA patients suggests that CII autoreactivity in RA may be more common than previously recognized.

Very high levels of anti-citrullinated protein antibodies are associated with HLA-DRB1*15 non-shared epitope allele in patients with rheumatoid arthritis.

OBJECTIVE: Production of anti-citrullinated protein antibodies (ACPAs) is an important biomarker for rheumatoid arthritis (RA). We undertook this study to determine whether genetic factors (HLA-DRB1 alleles) are associated with extreme ACPA levels in individuals with ACPA-positive RA, and to ascertain whether there are any phenotypic characteristics associated with these subgroups of RA. METHODS: HLA-DRB1 allelic groups were genotyped in 1,073 ACPA-positive RA patients from the Swedish Epidemiological Investigation of Rheumatoid Arthritis study. We found that 283 patients (26.4%) had high ACPA levels (defined as >1,500 units/ml using the Euro-Diagnostica anti-CCP2 test), while the rest of the patients had moderate ACPA levels and served as the comparison group. A replication group consisted of 235 RA patients. RESULTS: No significant differences in baseline disease activity were observed between patients with high and those with moderate ACPA levels. However, the HLA-DRB1*15 allele was associated with high ACPA levels (P=0.0002). A similar trend was detected in HLA-DRB1*15-positive patients in the replication cohort, with meta-analysis of the discovery and replication cohorts demonstrating an overall effect of HLA-DRB1*15 on development of high ACPA levels in both the discovery and replication cohorts (P<0.0001 by Mantel-Haenszel test with a fixed-effects model). CONCLUSION: Our data indicate that HLA-DRB1*15 may promote the production of high ACPA levels. Due to the high value of ACPA level scores in the 2010 American College of Rheumatology/European League Against Rheumatism classification criteria for RA, the presence of HLA-DRB1*15 may, at least in part, contribute to fulfilling the criteria for RA. This illustrates the complex nature of the genetic regulation of ACPA levels. Additional mechanistic studies of the regulation of ACPAs and ACPA-positive RA are pending.

Plasma levels of P-selectin and future risk of incident venous thromboembolism.

BACKGROUND: P-selectin levels are elevated following acute deep vein thrombosis and reported to predict recurrent venous thromboembolism (VTE) and cancer-associated VTE. Yet, it is unknown whether plasma P-selectin levels are associated with incident VTE. OBJECTIVES: We aimed to investigate the association between plasma P-selectin levels and risk of future incident VTE. METHODS: We performed a nested case-control study in 415 patients with VTE and 843 age- and sex-matched controls derived from the general population (Tromsø IV Study). Plasma P-selectin levels were measured using enzyme-linked immunosorbent assay. Logistic regression models were used to estimate odds ratios (ORs) for VTE across quartiles of plasma P-selectin level. Sex-stratified analysis was also performed. RESULTS: Plasma P-selectin levels were higher in men (41.4 ng/mL) than in women (38.7 ng/mL, p = .0046). We found no association between plasma P-selectin levels and risk of VTE in the overall analyses. However, sex-stratified analyses revealed that women with P-selectin levels in the highest quartile (>44.3 ng/mL) had higher risk of VTE (OR, 1.63; 95% CI, 1.01-2.64) than women with P-selectin levels in the lowest quartile (≤29.9 ng/mL). In contrast, higher levels of P-selectin were apparently associated with lower risk of VTE in men (OR for highest vs lowest quartile of P-selectin, 0.69; 95% CI, 0.42-1.15). The observed associations were stronger when the time between blood sampling and VTE was shorter. CONCLUSION: Elevated levels of plasma P-selectin were associated with increased risk of VTE in women but not in men, suggesting a differential impact of sex on the association between P-selectin and VTE risk.