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Targeting IL-17 has become an important option in the current treatment of spondyloarthritis (SpA). To place this therapeutic advancement in context, we review the discovery and properties of this cytokine, noting those which predispose to inflammation and led to it being considered as an attractive target for the treatment of arthritis, especially SpA. The processes that regulate the differentiation of IL-17-producing cells, particularly Th17 CD4+ T cells, have been investigated thoroughly, including the role of IL-23, as these point to additional potential therapies as alternatives to direct IL-17 blockade. IL-17 is a critical cytokine in combatting infection, particularly caused by fungi, but it also has an important role in maintaining epithelial barrier functions, especially in the gut. Both these functions help predict possible adverse effects of IL-17 blockade. Finally, we review the current evidence for the use of IL-17 blockade in various forms of SpA and briefly speculate on future developments., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This review is concerned with a number of recent publications that contribute to current thinking on the pathogenesis of spondyloarthritis. The areas covered include the lymphocyte population in the enthesis, which is thought to drive enthesitis, and hence clinical manifestations. The debate on how HLA-B27 is implicated in inflammation is also considered, together with recent and contradictory evidence on the effects of the peptide-trimming enzyme ERAP1 on B27 expression and hence susceptibility to spondylitis. Lastly, a recent report on the role of the gut microbiome in an important model of spondyloarthritis is considered., Competing Interests: Competing interests: The author declares that he has no competing interests.No competing interests were disclosed.No competing interests were disclosed.

Expression of the adhesion molecule, CD146/MCAM/MelCAM, on T cells has been associated with recent activation, memory subsets and T helper type 17 (Th17) effector function, and is elevated in inflammatory arthritis. Th17 cells have been implicated in the pathogenesis of rheumatoid arthritis (RA) and spondyloarthritides (SpA). Here, we compared the expression of CD146 on CD4(+) T cells between healthy donors (HD) and patients with RA and SpA [ankylosing spondylitis (AS) or psoriatic arthritis (PsA)] and examined correlations with surface markers and cytokine secretion. Peripheral blood mononuclear cells (PBMC) were obtained from patients and controls, and synovial fluid mononuclear cells (SFMC) from patients. Cytokine production [elicited by phorbol myristate acetate (PMA)/ionomycin] and surface phenotypes were evaluated by flow cytometry. CD146(+) CD4(+) and interleukin (IL)-17(+) CD4(+) T cell frequencies were increased in PBMC of PsA patients, compared with HD, and in SFMC compared with PBMC. CD146(+) CD4(+) T cells were enriched for secretion of IL-17 [alone or with IL-22 or interferon (IFN)-γ] and for some putative Th17-associated surface markers (CD161 and CCR6), but not others (CD26 and IL-23 receptor). CD4(+) T cells producing IL-22 or IFN-γ without IL-17 were also present in the CD146(+) subset, although their enrichment was less marked. Moreover, a majority of cells secreting these cytokines lacked CD146. Thus, CD146 is not a sensitive or specific marker of Th17 cells, but rather correlates with heterogeneous cytokine secretion by subsets of CD4(+) helper T cells., (© 2014 British Society for Immunology.)

Objective: To determine which of two referral strategies, when used by referring physicians for patients with chronic back pain (CBP), is superior for diagnosing axial spondyloarthritis (SpA) by rheumatologists across several countries., Methods: Primary care referral sites in 16 countries were randomised (1 : 1) to refer patients with CBP lasting >3 months and onset before age 45 years to a rheumatologist using either strategy 1 (any of inflammatory back pain (IBP), HLA-B27 or sacroiliitis on imaging) or strategy 2 (two of the following: IBP, HLA-B27, sacroiliitis, family history of axial SpA, good response to non-steroidal anti-inflammatory drugs, extra-articular manifestations). The rheumatologist established the diagnosis. The primary analysis compared the proportion of patients diagnosed with definite axial SpA by referral strategy., Results: Patients (N=1072) were referred by 278 sites to 64 rheumatologists: 504 patients by strategy 1 and 568 patients by strategy 2. Axial SpA was diagnosed in 35.6% and 39.8% of patients referred by these respective strategies (between-group difference 4.40%; 95% CI -7.09% to 15.89%; p=0.447). IBP was the most frequently used referral criterion (94.7% of cases), showing high concordance (85.4%) with rheumatologists' assessments, and having sensitivity and a negative predictive value of >85% but a positive predictive value and specificity of <50%. Combining IBP with other criteria (eg, sacroiliitis, HLA-B27) increased the likelihood for diagnosing axial SpA., Conclusions: A referral strategy based on three criteria leads to a diagnosis of axial SpA in approximately 35% of patients with CBP and is applicable across countries and geographical locales with presumably different levels of expertise in axial SpA.

Objective: To measure the frequencies of IL-4+ CD8+ T cells from patients with AS and RA, and to assess their clinical relevance and properties., Methods: Peripheral blood (PB) and clinical data were obtained from 37 AS, 36 RA patients and 37 healthy controls. We also generated IL-4-producing CD8+ T cell lines and clones by co-culture with autologous dendritic cells. Using flow cytometry, we evaluated intracellular cytokine expression by T cells following stimulation with PMA and calcium ionophore. The phenotype and ability of the IL-4-producing CD8+ T cell clones to suppress IFN-gamma production were examined., Results: The percentages of IL-4+ CD8+ T cells were higher in PB of patients with AS and RA than controls (medians 0.90 and 0.84% vs 0.30%). In RA, patients with active inflammation had an increased percentage of IL-4+ CD8+ T cells. Higher frequencies of IL-4+ CD8+ T cells were also found in CD8+ T cell lines established from patients with arthritis. Interestingly, most IL-4+ CD8+ T cells produced TNF-alpha. Cloning the CD8+ T cell lines yielded more IL-4-producing clones from AS (23%) and RA patients (14%) than from controls (7%). The ability to suppress IFN-gamma production was observed in 56% (AS) and 85% (RA) of IL-4-producing clones. Suppressive IL-4+ CD8+ T cell clones from RA patients showed a similar regulatory phenotype to the clones previously isolated from AS patients., Conclusions: Expansion of IL-4+ CD8+ T cells, which may include precursors of a regulatory CD8+ T cell subset, may represent a general response to chronic joint inflammation.

More than 20 yrs ago, T-helper lymphocytes were divided into Th1 and Th2 subsets on the basis of their cytokine production. The pro-inflammatory Th1 subset was considered predominant in inflammatory arthritis, but evidence for this notion was incomplete, and some called into question the role of helper T cells. The identification of a novel T cell subset, Th17 cells, which appears to be critical for several forms of autoimmune inflammation, including arthritis, requires a reconsideration of arthritis pathogenesis and the role of T cells. This review deals with several of the newly described ('big number') cytokines which are involved in the differentiation and action of Th17 cells, and pays particular attention to the pathogenesis of spondyloarthritis because of the implication of the same cytokine networks in psoriasis and inflammatory bowel disease. The role of dendritic cells as coordinators of T cell differentiation in response to pathogen-derived signals in also emphasized.

Background: Anti-heat-shock protein 60 (HSP60) antibody-levels have been linked to carotid atherosclerosis and cardiovascular risk in a variety of studies. The potential role of cellular immune reactions against HSP60 has so far attracted little attention in epidemiological research., Methods and Results: In vitro T-cell reactivity to various HSP60s and tuberculin was assessed in blood samples from a elderly subpopulation of the Bruneck study (100 men, 50-69 years) and the young participants of the ARMY study (141 men, 17-18 years), and analyzed for a potential association with common carotoid artery intima-media thickness (IMT). In vivo skin reaction against tuberculin was recorded in subjects of the Bruneck study and correlated with the in vitro proliferative response to tuberculin (P=0.004). T-cells isolated from peripheral blood of all individuals proliferated upon stimulation with HSP60s. In multivariate linear regression analysis adjusted for standard risk factors, T-cell stimulation was significantly related to IMT in the ARMY (P=0.005 for human HSP60 and P=0.064 for mycobacterial HSP60) but not in the Bruneck study., Conclusions: T-cell reactivity against HSP60s correlated with IMT in male youngsters but not in men aged 50 and over, indicating a more prominent role of specific cellular immunity to HSP60s in the young and very early stages of atherosclerosis.

Objectives: How human leucocyte antigen B27 (HLA-B27) contributes towards arthritis susceptibility is still unclear, but effects on the response to bacteria unrelated to the classical antigen presenting role of B27 have been suggested. This study investigated whether HLA-B27 modulates the innate response to lipopolysaccharide (LPS), a component shared between all Gram negative bacteria that can trigger reactive arthritis., Methods: Pools of U937 transfectants expressing either HLA-B27, HLA-A2 or the expression plasmid alone were differentiated with phorbol 12-myristate 13-acetate and stimulated with LPS. Supernatants were analysed for tumour necrosis factor-alpha (TNF-alpha) secretion and the gene expression profiles of unstimulated and LPS-stimulated cells were determined by microarray analysis. Changes in gene expression that are indicative of an unfolded protein response (UPR) were also analysed by quantitative polymerase chain reaction (PCR)., Results: TNF-alpha secretion, a biological marker of the inflammatory response to LPS, was not significantly different between U937-B27 and U937-control. No differences in gene expression between unstimulated U937-B27 and U937-control lines were detected. Both U937-control and U937-B27 exhibited a stereotypic response to LPS. Only one gene, OAS2, was differentially expressed by these cell lines, and this was confirmed by quantitative PCR. Analysis of XBP-1 splicing suggested that the UPR is induced following the LPS stimulation, but this increase was seen in all transfectants., Conclusions: The expression of B27 does not profoundly alter the gene expression following LPS stimulation. Therefore, additional signals, such as those provided by cytokines or intracellular infection, may be required to reveal any influence of B27 expression on the inflammatory response.

Background: The development of inhibitors in hemophiliacs is a severe complication of factor VIII (FVIII) replacement therapy and is a process driven by FVIII specific T helper cells., Objectives: To finely map T cell epitopes within the whole FVIII protein in order to investigate the possibility of engineering FVIII variants with reduced propensity for inhibitor development., Patients and Methods: T cell lines were generated from five patients with severe hemophilia who had developed inhibitors, and were screened for T cell proliferation against pools of overlapping peptides spanning the entire B domain deleted (BDD) FVIII sequence. Positive peptide pools were decoded by screening individual peptides against the T cell lines. Positive peptides, and mutants thereof, were tested for their ability to bind major histocompatibility complex (MHC) Class II and stimulate T cell proliferation in a panel of healthy donors. The activities of the corresponding mutant proteins were assessed via chromogenic assay., Results: One peptide, spanning FVIII amino acids 2098-2112, elicited a vigorous response from one hemophiliac donor, induced strong T cell responses in the panel of healthy donors and bound to a number of HLA-DR alleles. Mutations were made in this peptide that removed its ability to stimulate T cells of healthy donors and to bind to MHC Class II while retaining full activity when incorporated into a mutant BDD-FVIII protein., Conclusions: Fine T cell epitope mapping of the entire FVIII protein is feasible, although challenging, and this knowledge may be used to create FVIII variants which potentially have reduced immunogenicity.

Objective: To compare the cytokine expression profile of three CD8+, three CD4+, and three gammadelta+ T cell clones all derived from the synovial fluids of three patients with reactive arthritis (ReA)., Methods: Complementary DNA based microarrays containing the specific sequence of 56 cytokine transcripts were used for screening. Selected genes were confirmed by reverse transcriptase-polymerase chain reaction assay., Results: Microarray showed that transcripts encoding for interferon gamma and tumour necrosis factor alpha were expressed by all CD8+ and CD4+ T cell clones. However, gammadelta+ T cells predominantly expressed transforming growth factor beta2 and granulocyte monocyte-colony stimulating factor., Conclusion: T lymphocyte clones from the joint of patients with ReA exhibit differential cytokine expression profiles. CD8+ and CD4+ T cells demonstrate a Th1 mediated profile, whereas gammadelta+ T cells show a more heterogeneous and less proinflammatory Th3 driven pattern.

Natural killer (NK) cells are an important component of the immediate immune response to infections, including infection by intracellular bacteria. We have investigated recognition of Chlamydia trachomatis (CT) by NK cells and show that these cells are activated to produce interferon (IFN)-gamma when peripheral blood mononuclear cells (PBMC) are stimulated with CT organisms. Furthermore, infection of epithelial cell lines with CT renders them susceptible to lysis by human NK cells. Susceptibility was observed 18-24 h following infection and required protein synthesis by the infecting chlamydiae, but not by the host cell; heat or UV inactivated chlamydiae did not induce susceptibility to NK cell lysis. CT infection was also shown to decrease the expression of classical and non-classical major histocompatibility complex (MHC) molecules on infected cells, thus allowing recognition by NK cells when combined with an activating signal. A candidate activating signal is MICA/B, which was shown to be expressed constitutively on epithelial cells.

Objective: To determine the efficacy of weekly treatment with oral azithromycin for 13 weeks on the severity and resolution of reactive arthritis (ReA)., Methods: 186 patients from 12 countries were enrolled in a randomised, double blind, placebo controlled trial. Inclusion criteria were inflammatory arthritis of < or =6 swollen joints, and disease duration of < or =2 months. All patients received a single azithromycin dose (1 g) as conventional treatment for possible Chlamydia infection, and were then randomly allocated to receive weekly azithromycin or placebo. Clinical assessments were made at 4 week intervals for 24 weeks., Results: 152 patients were analysable (34 failed entry criteria), with a mean (SD) age of 33.8 (9.4) and duration of symptoms 30.7 (17.5) days. Mean C reactive protein (CRP) was 48 mg/l, and approximately 50% of those typed were HLA-B27+, suggesting that the inclusion criteria successfully recruited patients with acute ReA. Treatment and placebo groups were well matched for baseline characteristics. There were no statistical differences for changes in any end point (swollen and tender joint count, joint pain, back pain, heel pain, physician and patient global assessments, and CRP) between the active treatment and placebo groups, analysed on an intention to treat basis or according to protocol completion. The time to resolution of arthritis and other symptoms or signs by life table analyses was also not significantly different. Adverse events were generally mild, but were more commonly reported in the azithromycin group., Conclusions: This large trial has demonstrated that prolonged treatment with azithromycin is ineffective in ReA.

It is established that the molecular chaperone, chaperonin 60, from various bacteria and from Homo sapiens has cell-cell signalling activity and is able to induce proinflammatory cytokine synthesis. We previously reported that chaperonin 60 proteins from Gram-negative bacteria, but not mycobacteria, have the capacity to resorb cultured murine calvarial bone. We now report that lipopolysaccharide-low human recombinant chaperonin 60 (Hsp60) is a relatively weak cytokine-inducing agonist but is a potent stimulator of murine calvarial bone resorption. The osteolytic activity of Hsp60 was significantly inhibited by indomethacin, interleukin-1 receptor antagonist, and osteoprotegerin, but 5-lipoxygenase inhibitors were less effective. Analysis of Hsp60 truncation mutants revealed that N-terminal mutants (Delta1-137, Delta1-358, and Delta1-465) retained bone resorbing activity. In contrast, a C-terminal truncation mutant (Delta1-26 + Delta466-573) was inactive. This suggests that the active domain in this protein is found within residues 466-573. It is now established that Hsp60 is present in the blood of the majority of the population with the normal range encompassing levels able to activate bone cells. The possibility exists that this protein could play a role in bone remodelling.

Detection of antibodies to an outer membrane protein 2 (OMP2) by enzyme-linked immunosorbent assay (ELISA) by using either the Chlamydia trachomatis- or the Chlamydia pneumoniae-specific protein was investigated. OMP2 is an immunodominant antigen giving rise to antibody responses in humans infected with different C. trachomatis serovars (A to C and D to K) or with C. pneumoniae, which could be detected by OMP2 ELISA. OMP2 ELISA is not species specific, but antibody titers were usually higher on the homologous protein. The sensitivity of this assay was high but varied according to the "gold standard" applied. Levels of antibody to C. pneumoniae OMP2 as detected by ELISA seem to return to background or near-background values within a shorter period of time compared to antibodies to C. pneumoniae detected by microimmunofluorescence (MIF), making it more likely that positive results in ELISA reflect recent infection. Thus, OMP2 ELISA has distinct advantages over MIF and commercially available ELISAs and might be a useful tool for the serodiagnosis of chlamydial infection.

The aetiology of chronic prostatitis is not understood. The aim of this study is to investigate an autoimmune hypothesis by looking for T cell proliferation in response to proteins of the seminal plasma. We studied peripheral blood mononuclear cell proliferation from 20 patients with chronic prostatitis and 20 aged-matched controls in response to serial dilutions of seminal plasma (SP) from themselves (autologous SP) and from a healthy individual without the disease (allo-SP). We found that the patients have a statistically greater lymphocyte proliferation to autologous SP at the 1/50 dilution on day 6 compared to controls (P = 0 x 01). They also have a greater proliferation to allo-SP on both day 5 (P = 0 x 001) and day 6 (P = 0 x 01) at the same dilution. Using a stimulation index (SI) of 9 to either autologous SP or allo-SP on day 6 at the 1/50 dilution as a definition of a proliferative response to SP, then 13/20 patients as compared to 3/20 controls showed a proliferative response to SP (P = 0 x 003, Fishers exact test). These data support an autoimmune hypothesis for chronic prostatitis.