High-affinity antibodies reenter germinal centers (GCs) and limit antigen access, thus causing sustained directional evolution in GCs toward higher-affinity antibody production.

Background: Estimation of the intake of oily fish at a population level is difficult. The measurement of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in biological samples may provide a useful biomarker of intake.Objective: We identified the most appropriate biomarkers for the assessment of habitual oily fish intake and changes in intake by elucidating the dose- and time-dependent response of EPA and DHA incorporation into various biological samples that represent roles in fatty acid transport, function, and storage.Design: This was a double-blind, randomized, controlled intervention trial in 204 men and women that lasted 12 mo. EPA and DHA capsules were provided in a manner to reflect sporadic consumption of oily fish (ie, 1, 2, or 4 times/wk). EPA and DHA were assessed at 9 time points over 12 mo in 9 sample types (red blood cells, mononuclear cells, platelets, buccal cells, adipose tissue, plasma phosphatidylcholine, triglycerides, cholesteryl esters, and nonesterified fatty acids).Results: A dose response (P < 0.05) was observed for EPA and DHA in all pools except for red blood cell EPA (P = 0.057). EPA and DHA measures in plasma phosphatidylcholine and platelets were best for the discrimination between different intakes (P < 0.0001). The rate of incorporation varied between sample types, with the time to maximal incorporation ranging from days (plasma phosphatidylcholine) to months (mononuclear cells) to >12 mo (adipose tissue).Conclusions: Plasma phosphatidylcholine EPA plus DHA was identified as the most suitable biomarker of acute changes in EPA and DHA intake, and platelet and mononuclear cell EPA plus DHA were the most suitable biomarkers of habitual intake. This trial was registered at Current Controlled Trials (www.controlled-trials.com) as ISRCTN48398526.

Metabolomic studies of body fluids show that immune-mediated inflammatory diseases such as rheumatoid arthritis (RA) are associated with metabolic disruption. This is likely to reflect the increased bioenergetic and biosynthetic demands of sustained inflammation and changes in nutrient and oxygen availability in damaged tissue. The synovial membrane lining layer is the principal site of inflammation in RA. Here, the resident cells are fibroblast-like synoviocytes (FLS) and synovial tissue macrophages, which are transformed toward overproduction of enzymes that degrade cartilage and bone and cytokines that promote immune cell infiltration. Recent studies have shown metabolic changes in both FLS and macrophages from RA patients, and these may be therapeutically targetable. However, because the origins and subset-specific functions of synoviocytes are poorly understood, and the signaling modules that control metabolic deviation in RA synovial cells are yet to be explored, significant additional research is needed to translate these findings to clinical application. Furthermore, in many inflamed tissues, different cell types can forge metabolic collaborations through solute carriers in their membranes to meet a high demand for energy or biomolecules. Such relationships are likely to exist in the synovium and have not been studied. Finally, it is not yet known whether metabolic change is a consequence of disease or whether primary changes to cellular metabolism might underlie or contribute to the pathogenesis of early-stage disease. In this review article, we collate what is known about metabolism in synovial tissue cells and highlight future directions of research in this area.

Engagement of Fc␥ receptors (Fc␥Rs; ⌬H, ؊6.5 kcal mol ؊1 ; T⌬S, 1.9 kcal mol ؊1 ; ⌬C p , ؊160 cal mol ؊1 K ؊1 ). Removal of terminal galactose residues did not alter the thermodynamic parameters significantly. Outer-arm GlcNAc residues contributed significantly to thermal stability of the C H 2 domains but only slightly to sFc␥RIIb binding. Truncation of 1,3-and 1,6-arm mannose residues generates a linear trisaccharide core structure and resulted in a significantly decreased affinity, a less exothermic ⌬H, and a more negative ⌬C p for sFc␥RIIb binding, which may result from a conformational change coupled to complex formation. Deglycosylation of the C H 2 domains abrogated sFc␥RIIb binding and resulted in the lowest thermal stability accompanied with noncooperative unfolding. These results suggest that truncation of the oligosaccharides of IgG-Fc causes disorder and a closed disposition of the two C H 2 domains, impairing sFc␥RIIb binding.

Objective. Inflammatory arthritis is associated with systemic manifestations including alterations in metabolism. We used nuclear magnetic resonance (NMR) spectroscopy–based metabolomics to assess metabolic fingerprints in serum from patients with established rheumatoid arthritis (RA) and those with early arthritis.Methods. Serum samples were collected from newly presenting patients with established RA who were naive for disease-modifying antirheumatic drugs, matched healthy controls, and 2 groups of patients with synovitis of ≤3 months' duration whose outcomes were determined at clinical followup. Serum metabolomic profiles were assessed using 1-dimensional 1H-NMR spectroscopy. Discriminating metabolites were identified, and the relationships between metabolomic profiles and clinical variables including outcomes were examined.Results. The serum metabolic fingerprint in established RA was clearly distinct from that of healthy controls. In early arthritis, we were able to stratify the patients according to the level of current inflammation, with C-reactive protein correlating with metabolic differences in 2 separate groups (P < 0.001). Lactate and lipids were important discriminators of inflammatory burden in both early arthritis patient groups. The sensitivities and specificities of models to predict the development of either RA or persistent arthritis in patients with early arthritis were low.Conclusion. The metabolic fingerprint reflects inflammatory disease activity in patients with synovitis, demonstrating that underlying inflammatory processes drive significant changes in metabolism that can be measured in the peripheral blood. The identification of metabolic alterations may provide insights into disease mechanisms operating in patients with inflammatory arthritis.

ObjectiveAnti–tumor necrosis factor (anti-TNF) therapies are highly effective in rheumatoid arthritis (RA) and psoriatic arthritis (PsA), but a significant number of patients exhibit only a partial or no therapeutic response. Inflammation alters local and systemic metabolism, and TNF plays a role in this. We undertook this study to determine if the patient's metabolic fingerprint prior to therapy could predict responses to anti-TNF agents.MethodsUrine was collected from 16 RA patients and 20 PsA patients before and during therapy with infliximab or etanercept. Urine metabolic profiles were assessed using nuclear magnetic resonance spectroscopy. Discriminating metabolites were identified, and the relationship between metabolic profiles and clinical outcomes was assessed.ResultsBaseline urine metabolic profiles discriminated between RA patients who did or did not have a good response to anti-TNF therapy according to European League Against Rheumatism criteria, with a sensitivity of 88.9% and a specificity of 85.7%, with several metabolites contributing (in particular histamine, glutamine, xanthurenic acid, and ethanolamine). There was a correlation between baseline metabolic profiles and the magnitude of change in the Disease Activity Score in 28 joints from baseline to 12 months in RA patients (P = 0.04). In both RA and PsA, urinary metabolic profiles changed between baseline and 12 weeks of anti-TNF therapy. Within the responders, urinary metabolite changes distinguished between etanercept and infliximab treatment.ConclusionThe clear relationship between urine metabolic profiles of RA patients at baseline and their response to anti-TNF therapy may allow development of novel approaches to the optimization of therapy. Differences in metabolic profiles during treatment with infliximab and etanercept in RA and PsA may reflect distinct mechanisms of action.

Objectives: To develop an objective method of nailfold capillaroscopy (NFC), applicable to a wide age range of paediatric patients. To compare the morphological characteristics of the nailfold capillaries in different rheumatology patient groups and controls. Methods: A colour digital video camera attached to a stereomicroscope was used to capture nailfold capillary images. Computerised image processing was used to analyse and store data. Subsequent quantitative and qualitative morphological analysis was performed in the following paediatric patient and control groups: 18 children with connective tissue diseases (CTD: juvenile dermatomyositis, systemic sclerosis, and undifferentiated connective tissue disease), eight with systemic lupus erythematosus, nine with primary Raynaud's disease, three with primary vasculitis, 15 with juvenile idiopathic arthritis, 17 healthy children and 20 healthy adults. Images were analysed by a single assessor who was unaware of the patient details. Results: The NFC technique was simple to perform and gave reproducible results, although some intraand intersubject variation was noted. Capillary density and width was age related, with younger children having fewer and wider capillaries than older children and adults. Linear capillary density was significantly higher in healthy adults (mean (SD) 8.6 (1.6) capillaries/mm) compared with healthy children (HC 6.9 (0.9) capillaries/mm). The group with CTD had the most abnormal findings, with lower linear density (4.9 (1.7) capillaries/mm) and increased capillary loop width (10.7 (7.3) mm) compared with HC (3.5 (1.7) mm). In addition, 11/18 (61%) patients in the CTD group had more than two definitely abnormal capillaries in at least two nailfolds, an abnormality not seen in other subjects. Two qualitative measures, the degree of avascularity and general disarrangement of capillary pattern, were more commonly observed in the CTD group than in HC. The proportion of tortuous capillaries did not differ significantly between study groups. Conclusions: This study is unique in measuring objective quantitative and qualitative parameters of the nailfold vasculature across a wide spectrum of age and disease. Differences in capillary morphology and frequency in children with CTD compared with other paediatric diseases and healthy controls were demonstrated. In the clinical situation, an assessment of the general degree of disarrangement may offer a fast tool for assessment of the nailfold vasculature which correlates well with NFC data.

We sought to evaluate the diagnostic accuracy of metabolomic biomarker profiles in neurological conditions (idiopathic intracranial hypertension (IIH), multiple sclerosis (MS) and cerebrovascular disease (CVD) compared to controls with either no neurological disease or mixed neurological diseases). Spectra of CSF (n = 87) and serum (n = 72) were acquired using (1)H NMR spectroscopy. Multivariate pattern recognition analysis was used to identify disease-specific metabolite biomarker profiles. The metabolite profiles were then used to predict the diagnosis of a second cohort of patients (n = 25). CSF metabolite profiles were able to predict diagnosis with a sensitivity and specificity of 80% for both IIH and MS. The CVD serum metabolite profile was 75% sensitive and specific. On analysing the second patient cohort, the established metabolite biomarker profiles generated from the first cohort showed moderate ability to segregate patients with IIH and MS (sensitivity:specificity of 63:75% and 67:75%, respectively). These findings suggest that NMR spectroscopic metabolic profiling of CSF and serum can identify differences between IIH, MS, CVD and mixed neurological diseases. Metabolomics may, therefore, have the potential to be developed into a clinically useful diagnostic tool. The identification of disease-unique metabolites may also impart information on disease pathology.