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Concept: Rheumatoid factor


Presence of autoantibodies precedes development of seropositive rheumatoid arthritis (SP RA) and seropositive arthralgia patients (SAP) are at risk of developing RA. The aims of the study are to identify additional serum immune markers discriminating between SP and seronegative (SN) RA, and markers identifying high-risk SAP. Sera from SAP (n = 27), SP RA (n = 22), SN RA (n = 11) and healthy controls (n = 20) were analyzed using the Human Cytokine 25-Plex Panel. Selected markers were validated in independent cohorts of SP RA (n = 35) and SN RA (n = 12) patients. Eleven of 27 SAP developed RA within 8 months (median follow-up time, range 1-32 months), and their baseline serum markers were compared to 16 non-progressing SAP. SAP and SP RA patients showed a marked overlap in their systemic immune profiles, while SN RA showed a distinct immune profile. Three of 4 markers discriminating between SP and SN RA (IL-1β, IL-15 and Eotaxin, but not CCL5) were similarly modulated in independent cohorts. SAP progressing to RA showed trends for increases in IL-5, MIP-1β, IL-1RA and IL-12 compared to non-progressing SAP. ROC analysis showed that serum IL-5 most accurately discriminated between the two SAP groups (AUC > 0.8), suggesting that baseline IL-5 levels may aid the identification of high-risk SAP.

Concepts: Immunology, Rheumatoid arthritis, Rheumatology, Systemic lupus erythematosus, Arthritis, Identification, Rheumatoid factor


We investigated whether citrullinated tenascin-C (cTNC), an extracellular matrix protein expressed at high levels in the joints of patients with rheumatoid arthritis (RA), is a target for the autoantibodies in RA.

Concepts: Inflammation, Bone, Collagen, Extracellular matrix, Rheumatoid arthritis, Rheumatology, Osteoarthritis, Rheumatoid factor


This study aims to measure the serum level of 25-hydroxyvitamin D(3) (25-OH-D(3)) in 302 patients with rheumatoid arthritis (RA), studying the association to disease activity. Three hundred two RA patients underwent clinical examination and serological analysis. 25-Hydroxyvitamin D(3) was determined by high-performance liquid chromatography-tandem mass spectrometry. Vitamin D(3) deficiency defined as serum levels of 25-hydroxyvitamin D(3) below 50 nmol/l was detected in 101 RA patients (33.4 %). There was no significant correlation between the serum level of 25-hydroxyvitamin D(3) and Disease Activity Score 28 (DAS28) (3w) score. In a subpopulation of RA patients with very low serum level of 25-OH-D(3) (≤15 nmol/l) (n = 15), there were significant differences compared to patients with normal 25-OH-D(3) (n = 200): higher percentage of patients with positive rheumatoid factor (100.0 versus 77.5 %; p = 0.05), higher CRP (28.7 versus 14.8 mg/l; p = 0.001), higher number of patients treated with at least three disease-modifying antirheumatic drugs (DMARDs) (40.0 versus 14.5 %; p = 0.02), higher number of patients with high disease activity DAS28 score of ≥5.1 (20.0 versus 4.5 %; p = 0.01), lower age (54.5 versus 64.0 years; p = 0.003) and shorter disease duration (5.1 versus 10.3 years; p = 0.06). Deficiency of 25-hydroxyvitamin D(3) was detected in 33.4 % of the RA patients. A subpopulation of patients with severe deficiency of vitamin D(3) serum level of ≤15 nmol/l was characterised by all being positive for rheumatoid factor, high percentage of patients with very high disease activity and high percentage of patients treated with at least three DMARDs.

Concepts: Immunology, Rheumatoid arthritis, Rheumatology, Arthritis, Liquid chromatography-mass spectrometry, Disease-modifying antirheumatic drug, Hydroxychloroquine, Rheumatoid factor


The major strides accomplished in elucidating the pathophysiology of rheumatoid arthritis (RA) have translated into therapeutic breakthroughs in clinical practice. However, currently available treatments work only for as long as they are taken. The development of curative treatments will probably require a better understanding of the earliest phases of RA and perhaps the identification of the etiological factors, which are probably numerous. These objectives are being pursued in studies of preclinical RA. The literature review presented herein indicates that the immunological conflict probably originates outside the joints, at mucous membrane sites and, more specifically, in the upper aerodigestive tract. The preclinical phase of RA can last for many years, and some patients probably never progress to arthritis. An immunological conflict develops then spins out of control, causing increases in autoantibody titers and subsequently in levels of serum markers for inflammation, before the development of the first joint symptoms. Improved knowledge of the preclinical phase, together with information from genetic markers, will allow the identification of profiles associated with susceptibility to RA and perhaps, in the future, the development of preventive strategies.

Concepts: Medicine, Mucous membrane, Rheumatoid arthritis, Rheumatology, Osteoarthritis, Philosophy of science, Phase, Rheumatoid factor


The presence of anti-citrullinated protein antibodies (ACPA) and IgM-rheumatoid factor (IgM-RF) years before the clinical diagnosis of rheumatoid arthritis (RA) suggests they are possibly involved in the pathogenic process underlying RA. In this study, we analysed whether anti-carbamylated protein (anti-CarP) antibodies, a novel autoantibody system against carbamylated proteins, can also be detected in healthy individuals before they developed RA.

Concepts: Immune system, Antibody, Protein, Nutrition, Rheumatoid arthritis, Rheumatology, Antibodies, Rheumatoid factor


Binding of cross-reactive autoantibodies to peptidylarginine deiminase 4 (PAD4) increases its activity by lowering its requirement for Ca(2+), leading to increased production of citrullinated autoantigens and worse outcomes in patients with rheumatoid arthritis (Darrah et al., this issue).

Concepts: Disease, Infectious disease, Medical terms, Rheumatoid arthritis, Rheumatology, Arthritis, Autoimmunity, Rheumatoid factor


The pre-symptomatic stage of Rheumatoid arthritis (RA) is associated with pro-inflammatory cytokines and autoantibodies. High levels and epitope spread by Rheumatoid factors (RhF) and autoantibodies to citrullinated proteins signify progression towards disease expression. In established RA, the persistence of high autoantibody levels reflects production by both long-lived plasma cells and short-lived plasmablasts. Neither the relative contributions to pathogenesis by autoantibodies from either source, nor the factors responsible for deciding the fate of autoantigen specific ‘parent’ B-cells, is understood. Phenotypic markers identifying subsets of autoreactive B-cells are therefore of interest in understanding the origin and perpetuation of the autoimmune response in RA. One such phenotypic marker is the rat monoclonal antibody, 9G4, which recognises an idiotope on immunoglobuins derived from the inherently autoreactive VH-gene, VH4-34. We therefore investigated whether the 9G4 idiotope was expressed on autoantibodies in patients with RA.

Concepts: Immune system, Antibody, Protein, Immunology, B cell, Rheumatoid arthritis, Autoimmune diseases, Rheumatoid factor


Immune checkpoint inhibitors (ICIs) targeting the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) pathways have demonstrated survival improvements in multiple advanced cancers, but also cause immune-related adverse events (IRAEs). IRAEs with clinical features similar to rheumatic diseases have not been well described. We report patients with inflammatory arthritis and sicca syndrome secondary to ICIs.

Concepts: Cell, Rheumatoid arthritis, Rheumatology, Systemic lupus erythematosus, Sjögren's syndrome, Programmed cell death, Autoimmunity, Rheumatoid factor


We carried out metagenomic shotgun sequencing and a metagenome-wide association study (MGWAS) of fecal, dental and salivary samples from a cohort of individuals with rheumatoid arthritis (RA) and healthy controls. Concordance was observed between the gut and oral microbiomes, suggesting overlap in the abundance and function of species at different body sites. Dysbiosis was detected in the gut and oral microbiomes of RA patients, but it was partially resolved after RA treatment. Alterations in the gut, dental or saliva microbiome distinguished individuals with RA from healthy controls, were correlated with clinical measures and could be used to stratify individuals on the basis of their response to therapy. In particular, Haemophilus spp. were depleted in individuals with RA at all three sites and negatively correlated with levels of serum autoantibodies, whereas Lactobacillus salivarius was over-represented in individuals with RA at all three sites and was present in increased amounts in cases of very active RA. Functionally, the redox environment, transport and metabolism of iron, sulfur, zinc and arginine were altered in the microbiota of individuals with RA. Molecular mimicry of human antigens related to RA was also detectable. Our results establish specific alterations in the gut and oral microbiomes in individuals with RA and suggest potential ways of using microbiome composition for prognosis and diagnosis.

Concepts: Immune system, Bacteria, Gut flora, Rheumatoid arthritis, Rheumatology, Carbon, Lactobacillus, Rheumatoid factor


Anticarbamylated protein (anti-CarP) antibodies are a novel family of autoantibodies recently identified in patients with inflammatory arthritis. The aim of this study was to investigate their association with long-term outcomes of disability and disease activity over 20 years' follow-up in a cohort of patients with inflammatory polyarthritis (IP).

Concepts: Antibody, Rheumatoid arthritis, Osteoarthritis, Arthritis, Abraham Lincoln, Rheumatoid factor