Regulatory T cells enhance Th17 migration in psoriatic arthritis which is reversed by anti-TNF.

Regulatory T cells (Treg) prevent the migration of effector T cells toward sites of inflammation, thereby limiting disease progression. We investigated this aspect of Treg function using psoriatic arthritis (PsA) as an exemplar of chronic inflammation. Patients with PsA had an increased Th17:Treg ratio which was reversed by anti-tumor necrosis factor (TNF) therapy. Utilizing an in vitro migration assay, Treg from patients with PsA treated with conventional therapy paradoxically boosted CCR6+ effector T-cell (a surrogate for Th17) migration toward CCL20. In contrast, Treg from patients with PsA treated with anti-TNF suppressed CCL20-driven effector T-cell migration. The boosting effect of TNF blockade upon Treg suppression of migration was accompanied by increased effector T-cell CCL20 production and enhanced interaction between Treg and effector T cells. This study provides mechanistic insight into Treg modulation of effector T-cell migration in patients with chronic inflammation and how this can be targeted by therapy.

Elevated ACKR2 expression is a common feature of inflammatory arthropathies.

Objectives: Chemokines are essential contributors to leucocyte accumulation at sites of inflammatory pathology. Interfering with chemokine or chemokine receptor function therefore represents a plausible therapeutic option. However, our currently limited understanding of chemokine orchestration of inflammatory responses means that such therapies have not yet been fully developed. We have a particular interest in the family of atypical chemokine receptors that fine-tune, or resolve, chemokine-driven responses. In particular we are interested in atypical chemokine receptor 2 (ACKR2), which is a scavenging receptor for inflammatory CC-chemokines and that therefore helps to resolve in vivo inflammatory responses. The objective of the current study was to examine ACKR2 expression in common arthropathies. Methods: ACKR2 expression was measured by a combination of qPCR and immuno-histochemistry. In addition, circulating cytokine and chemokine levels in patient plasma were assessed using multiplexing approaches. Results: Expression of ACKR2 was elevated on peripheral blood cells as well as on leucocytes and stromal cells in synovial tissue. Expression on peripheral blood leucocytes correlated with, and could be regulated by, circulating cytokines with particularly strong associations being seen with IL-6 and hepatocyte growth factor. In addition, expression within the synovium was coincident with aggregates of lymphocytes, potentially atopic follicles and sites of high inflammatory chemokine expression. Similarly increased levels of ACKR2 have been reported in psoriasis and SSc. Conclusion: Our data clearly show increased ACKR2 in a variety of arthropathies and taking into account our, and others', previous data we now propose that elevated ACKR2 expression is a common feature of inflammatory pathologies.

Microarray analyses demonstrate the involvement of type I interferons in psoriasiform pathology development in D6-deficient mice.

The inflammatory response is normally limited by mechanisms regulating its resolution. In the absence of resolution, inflammatory pathologies can emerge, resulting in substantial morbidity and mortality. We have been studying the D6 chemokine scavenging receptor, which played an indispensable role in the resolution phase of inflammatory responses and does so by facilitating removal of inflammatory CC chemokines. In D6-deficient mice, otherwise innocuous cutaneous inflammatory stimuli induce a grossly exaggerated inflammatory response that bears many similarities to human psoriasis. In the present study, we have used transcriptomic approaches to define the molecular make up of this response. The data presented highlight potential roles for a number of cytokines in initiating and maintaining the psoriasis-like pathology. Most compellingly, we provide data indicating a key role for the type I interferon pathway in the emergence of this pathology. Neutralizing antibodies to type I interferons are able to ameliorate the psoriasis-like pathology, confirming a role in its development. Comparison of transcriptional data generated from this mouse model with equivalent data obtained from human psoriasis further demonstrates the strong similarities between the experimental and clinical systems. As such, the transcriptional data obtained in this preclinical model provide insights into the cytokine network active in exaggerated inflammatory responses and offer an excellent tool to evaluate the efficacy of compounds designed to therapeutically interfere with inflammatory processes.

An investigation of the inflammatory cytokine and chemokine network in systemic sclerosis.

OBJECTIVES: Systemic sclerosis (SSc) is characterised by vasculopathy, an aberrantly activated immune system and excessive extracellular matrix deposition. Inflammatory chemokines control migration of cells to sites of tissue damage; their removal from inflamed sites is essential for resolution of the inflammatory response. The atypical chemokine receptor D6 has a critical role in this physiological balance. To explore potential deregulation of this system in SSc, inflammatory chemokine and D6 expression were compared with that in healthy controls (HC). METHODS: Serum levels of inflammatory mediators were assessed by luminex analysis. Peripheral blood mononuclear cells (PBMCs) were used in molecular and immunocytochemical analysis. Platelet-rich plasma was collected and assessed by western blotting for D6 expression levels. Sex-matched HC were used for comparison. RESULTS: 72 patients with SSc and 30 HC were enrolled in the study. The chemokines MCP-1/CCL2, MIP-1α/CCL3, MIP-1ß/CCL4 and IL-8/CXCL8 were significantly increased in patients with SSc, regardless of disease subtype and phase. Quantitative PCR analysis revealed a significant 10-fold upregulation of D6 transcripts in patients with SSc compared with controls, and this was paralleled by increased D6 protein expression in the PBMCs of patients with SSc. Platelet lysates also showed strong D6 expression in patients with SSc but not in controls. Importantly, high levels of D6 expression correlated with reduced levels of its ligands in serum. CONCLUSIONS: Inflammatory chemokines and the regulatory receptor D6 are significantly upregulated in SSc and high D6 levels are associated with lower systemic chemokine levels, indicating that some patients control systemic chemokine levels using D6. These results suggest that chemokines may represent a therapeutic target in SSc.

Tumour necrosis factor alpha blockade impairs dendritic cell survival and function in rheumatoid arthritis.

OBJECTIVES: Tumour necrosis factor alpha (TNFalpha) blockade is an effective therapy for rheumatoid arthritis (RA). The immunomodulatory effects of TNFalpha antagonists are thought to contribute to their therapeutic action. This study investigated whether anti-TNFalpha therapeutics exerted their immunoregulatory effects through modulation of dendritic cell (DC) function. METHODS: Two complementary approaches were taken: in the first 'in vitro' approach monocyte-derived DC from healthy donors were matured with lipopolysaccharide and treated with TNFalpha antagonists in vitro for 48 h. In the second 'ex vivo' approach monocyte-derived DC were generated from RA patients before and 8-12 weeks into anti-TNFalpha treatment. DC were analysed for survival, phenotype, cytokine production and T-cell stimulatory capacity. RESULTS: TNFalpha blockade during DC maturation in vitro induced approximately 40% of DC to undergo apoptosis. Importantly, the surviving DC displayed a semimature phenotype with reduced levels of HLA-DR, CD80, CD83, CD86 and CCR7, and their production of IL-10 was enhanced compared with DC matured without TNFalpha antagonists. Furthermore, anti-TNFalpha-treated DC were poor stimulators of T-cell proliferation and polarised T-cell development towards a higher IL-10/lower IFNgamma cytokine profile. Similarly, DC derived from RA patients after anti-TNFalpha treatment showed impaired upregulation of CD80 and CD86 upon lipopolysaccharide activation and displayed poor T-cell stimulatory activity. CONCLUSIONS: The data show that TNFalpha blockade has profound effects on DC function with downstream, potentially immunoregulatory, effects on T cells. These data provide an interesting new insight into the potential mechanism by which anti-TNFalpha drugs contribute to the restoration of immunoregulation in RA patients.