Objective
The importance of interleukin‐17A (IL‐17A) in the pathogenesis of axial spondyloarthritis (SpA) has been demonstrated by the success of IL‐17A blockade. However, the nature of the cell ...populations that produce this important proinflammatory cytokine remains poorly defined. We undertook this study to characterize the major IL‐17A–producing blood cell populations in the peripheral blood of patients with axial SpA, with a focus on mucosal‐associated invariant T (MAIT) cells, a population known to be capable of producing IL‐17.
Methods
We evaluated IL‐17A production from 5 sorted peripheral blood cell populations, namely, MAIT cells, γδ T cells, CD4+ T cells, CD8+ T cells, and neutrophils, before and after stimulation with phorbol myristate acetate, the calcium ionophore A23187, and β‐1,3‐glucan. Expression of IL‐17A transcripts and protein were determined using nCounter and ultra‐sensitive Simoa technology, respectively. MAIT cells from the axial entheses of non‐axial SpA control patients (n = 5) were further characterized using flow cytometric immunophenotyping and quantitative polymerase chain reaction, and the production of IL‐17 was assessed following stimulation.
Results
On a per‐cell basis, MAIT cells from peripheral blood produced the most IL‐17A compared to CD4+ T cells (P < 0.01), CD8+ T cells (P < 0.0001), and γδ T cells (P < 0.0001). IL‐17A was not produced by neutrophils. Gene expression analysis also revealed significantly higher expression of IL17A and IL23R in MAIT cells. Stimulation of peripheral blood MAIT cells with anti‐CD3/CD28 and IL‐7 and/or IL‐18 induced strong expression of IL17F. MAIT cells were present in the normal, unaffected entheses of control patients who did not have axial SpA and showed elevated AHR, JAK1, STAT4, and TGFB1 transcript expression with inducible IL‐17A protein. IL‐18 protein expression was evident in spinal enthesis digests.
Conclusion
Both peripheral blood MAIT cells and resident MAIT cells in normal axial entheses contribute to the production of IL‐17 and may play important roles in the pathogenesis of axial SpA.
Objective
To assess the efficacy of etanercept in the treatment of early active nonsteroidal antiinflammatory drug (NSAID)–refractory nonradiographic axial spondyloarthritis (SpA).
Methods
The study ...population consisted of patients who met the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial SpA but not the modified New York radiographic criteria for ankylosing spondylitis (as assessed by a radiologist at the central trial site), had a symptom duration of >3 months but <5 years, had a score of ≥4 on the Bath Ankylosing Spondylitis Disease Activity Index, and had been treated unsuccessfully with ≥2 NSAIDs. Patients were randomized to receive etanercept 50 mg/week or placebo and continued background NSAID treatment for 12 weeks (double‐blind study); during the subsequent open‐label period, all patients received etanercept 50 mg/week. The primary study end point was meeting the ASAS criteria for 40% improvement (ASAS40) at week 12. Magnetic resonance imaging (MRI) of the sacroiliac joints and spine was performed at baseline and week 12.
Results
One hundred six patients were randomized to the etanercept group and 109 to the placebo group. Of the 215 patients, the mean ± SD age at baseline was 32.0 ± 7.8 years, 154 (72%) were HLA–B27 positive, and 174 (81%) had MRI‐confirmed sacroiliitis. At 12 weeks, the proportion of patients with improvement according to the ASAS40 was significantly higher in the etanercept group than in the placebo group (34 of 105 32% versus 17 of 108 16%; P = 0.006). Patients who received etanercept exhibited a greater reduction in MRI‐based scores for sacroiliac joint inflammation (−46.9% versus −10.9%; P < 0.001) and spinal inflammation (−45.4% versus −33.4%; P = 0.04) compared with placebo‐treated patients at week 12. Post hoc analyses suggested a possible association between higher baseline C‐reactive protein levels or MRI sacroiliac joint inflammation scores and higher rates of ASAS40 response to etanercept. At week 24, patients in the placebo group who had switched to etanercept at 12 weeks exhibited improvement similar to that observed in patients who had received etanercept for 24 weeks.
Conclusion
In patients with nonradiographic axial SpA, etanercept treatment was associated with rapid, significant improvement in symptomatic disease activity, function, and systemic and skeletal inflammation over 12 weeks; clinical/functional improvement was sustained over 24 weeks.
Spondyloarthritis (SpA) is a chronic inflammatory rheumatism characterized by inflammation of sacroiliac joints, peripheral joints, and spine. The Assessment of SpondyloArthritis Society describes ...three disease forms: axial (axSpA), peripheral, and enthesitic SpA. Each may be associated with extra-articular manifestations: psoriasis, inflammatory bowel disease, and acute anterior uveitis. Genome-wide association studies performed in axSpA and psoriatic arthritis (PsA) have shown a shared genetic background, especially the interleukin 23 (IL-23)/IL-17 pathway, which suggests pathophysiological similarities. The convincing positive results of clinical trials assessing the effect of secukinumab and ixekizumab (anti-IL-17A monoclonal antibodies) in axSpA and PsA have reinforced the speculated crucial role of IL-17 in SpA. Nevertheless, and obviously unexpectedly, the differential efficacy of anti-IL-23-targeted treatments between axSpA (failure) and PsA (success) has profoundly disrupted our presumed knowledge of disease pathogeny. The cells able to secrete IL-17, their dependence on IL-23, and their respective role according to the clinical form of the disease is at the heart of the current debate to potentially explain these observed differences in efficacy of IL-23/IL-17-targeted therapy. In fact, IL-17 secretion is usually mainly related to T helper 17 lymphocytes. Nevertheless, several innate immune cells express IL-23 receptor and can produce IL-17. To what extent these alternative cell populations can produce IL-17 independent of IL-23 and their respective involvement in axSpA and PsA are the crucial scientific questions in SpA. From this viewpoint, this is a nice example of a reverse path from bedside to bench, in which the results of therapeutic trials allow for reflecting more in depth on the pathophysiology of a disease. Here we provide an overview of each innate immunity-producing IL-17 cell subset and their respective role in disease pathogeny at the current level of our knowledge.
Cell stimulation leads to the shedding of phosphatidylserine (PS)-rich microparticles (MPs). Because autoimmune diseases (AIDs) are characterized by cell activation, we investigated level of ...circulating MPs as a possible biomarker in primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
We measured plasma levels of total, platelet and leukocyte MPs by prothrombinase capture assay and flow cytometry in 43 patients with pSS, 20 with SLE and 24 with RA and in 44 healthy controls (HCs). Secretory phospholipase A2 (sPLA2) activity was assessed by fluorometry. Soluble CD40 ligand (sCD40L) and soluble P-selectin (sCD62P), reflecting platelet activation, were measured by ELISA.
Patients with pSS showed increased plasma level of total MPs (mean +/- SEM 8.49 +/- 1.14 nM PS equivalent (Eq), P < 0.0001), as did patients with RA (7.23 +/- 1.05 n PS Eq, P = 0.004) and SLE (7.3 +/- 1.25 nM PS Eq, P = 0.0004), as compared with HCs (4.13 +/- 0.2 nM PS Eq). Patients with AIDs all showed increased level of platelet MPs (P < 0.0001), but only those with pSS showed increased level of leukocyte MPs (P < 0.0001). Results by capture assay and flow cytometry were correlated. In patients with high disease activity according to extra-glandular complications (pSS), DAS28 (RA) or SLEDAI (SLE) compared with low-activity patients, the MP level was only slightly increased in comparison with those having a low disease activity. Platelet MP level was inversely correlated with anti-DNA antibody level in SLE (r = -0.65; P = 0.003) and serum beta2 microglobulin level in pSS (r = -0.37; P < 0.03). The levels of total and platelet MPs were inversely correlated with sPLA2 activity (r = -0.37, P = 0.0007; r = -0.36, P = 0.002, respectively). sCD40L and sCD62P concentrations were significantly higher in pSS than in HC (P < or = 0.006).
Plasma MP level is elevated in pSS, as well as in SLE and RA, and could be used as a biomarker reflecting systemic cell activation. Level of leukocyte-derived MPs is increased in pSS only. The MP level is low in case of more severe AID, probably because of high secretory phospholipase A2 (sPLA2) activity, which leads to consumption of MPs. Increase of platelet-derived MPs, sCD40L and sCD62P, highlights platelet activation in pSS.
B cell activating factor (BAFF) plays a key role in promoting B lymphocyte activation. We investigated whether danger signals induce BAFF secretion by cultured salivary gland epithelial cells (SGEC), ...which are the target of primary Sjögren's syndrome, a prototypic systemic autoimmune disease. SGEC cultures were established from minor salivary glands obtained from ten patients with pSS or sicca symptoms. BAFF mRNA and protein were measured after stimulation of the different Toll-like receptors (TLR) by agonists or viruses. The expression of TLR2, -3, and -7 was detected in SGEC. Poly (I:C) (a synthetic TLR3 agonist) and reovirus-1 (a dsRNA virus) induced high expression of BAFF mRNA (multiplied by a factor of 246 ± 39 (SEM) and 347 ± 66, respectively) and of BAFF protein secretion (58.49 ± 4.34 pg/mL and 69.73 ± 5.67). Inhibition of both the endosomal (by chloroquine) and IFN (by anti-IFNAR antibody) pathways partly inhibited BAFF expression. Treatment with both dsRNA virus and poly (I:C) induced high levels of BAFF mRNA and protein expression by SGEC, through pathways dependent on and independent of TLR and dependent on and independent of IFN. BAFF induction by target organs of autoimmune diseases after viral infection may be a link between innate immunity and autoimmunity.
Background: The cytokine B cell-activating factor of the TNF family (BAFF) is involved in the pathogenesis of autoimmune diseases. Objective: To access changes in serum protein and mRNA levels of ...BAFF after rituximab treatment. Methods: Serum and peripheral blood mononuclear cells (PBMCs) were isolated from five patients (two with lupus, two with Sjögren’s syndrome, one with rheumatoid arthritis) before and 12 weeks (range 7–17) after a first course of rituximab infusion. Monocytes and B cells were selected from healthy controls and cocultured for 72 h. BAFF protein and mRNA levels were assessed by ELISA and real-time PCR, respectively. Results: After rituximab treatment, median serum BAFF protein level and BAFF to actin mRNA ratio in PBMCs significantly increased. In monocytes cocultured with autologous B cells, BAFF protein level decreased, whereas the mRNA level was stable. In one closely monitored patient, the mRNA ratio of BAFF to actin in PBMCs increased later than the BAFF serum level. Conclusions: Two distinct mechanisms are probably involved in the increase in BAFF level after B cell depletion: (1) the decrease in its receptors leading to a release of BAFF; (2) a delayed regulation of BAFF mRNA transcription. This could favour the re-emergence of autoreactive B cells.
Objective
Migration of B cells from peripheral blood to the synovium in patients with rheumatoid arthritis (RA) may predict clinical response to rituximab (RTX). We undertook this study to ...investigate whether serum levels of chemokines involved in B cell trafficking are correlated with blood levels of memory B cells or serum levels of B cell activation biomarkers before B cell depletion and whether chemokine levels predict RTX responsiveness.
Methods
Blood B cell subsets were analyzed by flow cytometry (CD27, IgD), and serum B cell activation biomarkers (rheumatoid factor, anti–cyclic citrullinated peptide, free light chains, IgG, IgA, IgM, and BAFF) were measured in 208 RA patients and 70 control subjects. Serum CCL19, CXCL12, and CXCL13 chemokine levels in patients and controls were determined by enzyme‐linked immunosorbent assay. The first course of RTX was administered to RA patients, and the response was evaluated at week 24 according to European League Against Rheumatism (EULAR) criteria. Results were expressed as the odds ratio (OR) and 95% confidence interval (95% CI).
Results
Levels of all chemokines were increased in RA patients compared with controls, and levels were inversely correlated with CD27+ memory B cell frequency. CCL19 and CXCL13 levels correlated with levels of 6 serum B cell biomarkers and 4 serum B cell biomarkers, respectively. By univariate analysis, the CCL19 level was positively associated with EULAR response (OR 1.43 95% CI 1.08–1.90, P = 0.01). By multivariate analysis, the CCL19 level was predictive of a response to RTX (OR 1.48 95% CI 1.06–2.06, P = 0.02), but this did not persist after adjustment for autoantibody status.
Conclusion
CXCL13 and CCL19 reflect blood B cell disturbances and their levels correlate with those of other serum B cell biomarkers. CXCL13 and CCL19 are, therefore, surrogate measures for serum B cell biomarkers in RA. Serum CCL19 measurement is a new hallmark of the B cell–mediated RA subtype and may predict clinical response to RTX.
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