The role of tumour necrosis factor (TNF-α) in experimental autoimmune uveoretinitis (EAU)
The pleiotropic cytokine tumour necrosis factor-alpha (TNF-alpha) is released from cells that include macrophages and T-cells during inflammatory responses, orchestrating the initiation of further leucocytic infiltration via adhesion molecule upregulation, dendritic cell maturation and survival, macrophage activation and driving Th1 T-cells responses within tissues. Exposure to TNF also plays a role in maintaining tissue homeostasis, particularly relating to resident cell responses of both microglia and retinal pigment epithelium. Depending on the balance between duration and dose of TNF exposure, an environment where full expression of inflammatory and autoimmune responses within tissues may occur. In experimental autoimmune uveoretinitis (EAU), increased tissue concentrations of TNF facilitate the on-going T-cell effector responses and macrophage activation. These are responsible for targeted and bystander tissue damage and can be suppressed by anti-TNF therapies, in particular, those directed at the p55 TNF receptor. The ability to suppress disease experimentally has led to the successful translation of anti-TNF therapy for treatment of uveitis in cohort studies and phase I/II trials where, additionally, altered peripheral blood CD4(+) T-cell profiles can be demonstrated following each treatment.
Available from: Chi-Chao Chan
- "Experimentally, we consistently observe that the tissue is protected following neutralisation of TNF-α activity, or by reprogramming myeloid cell activation threshold with CD200R treatment. Not surprisingly, therefore, anti-TNF-α agents provide clinical benefit in human disease ([97–99], and see below). "
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ABSTRACT: The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of Treg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8(+) T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders.
Available from: Martina Angi
- "Some authors have suggested that TNF-α participates actively in the pathogenesis of uveitis, although it seems to have a more important role systemically rather than locally. In animal models, it has been demonstrated that experimentally induced autoimmune uveoretinitis is CD4+Th1 dependent.22 A chronically activated T-cell produces, directly and indirectly, not only TNF-α, but also IL-1, IL-6, chemokines such as IL-8, inhibiting factors of macrophages, and metalloproteinases. "
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ABSTRACT: Juvenile idiopathic arthritis-related uveitis is the most common type of uveitis in childhood and one of the main causes of visual impairment in children. The introduction of biological treatment has widened the range of therapeutic options for children with uveitis refractory to standard nonbiologic immunosuppressants. Data from clinical trials suggest that both adalimumab and infliximab have demonstrated effectiveness and safety in open-label studies, although no large, randomized, controlled trials have been reported so far. The role of etanercept in treating juvenile idiopathic arthritis-related uveitis is not yet well defined. In our experience, anti-tumor necrosis factor therapy has been shown to be more effective than steroids and/or methotrexate in treating uveitis. Up to now, tumor necrosis factor blocking compounds have been reserved for the treatment of the most severe cases of refractory uveitis, and larger prospective clinical trials are required in order to better assess the safety of these new compounds.
Available from: Dalia Dawoud
- "Studies utilising experimental models of autoimmune uveitis have demonstrated that TNF-α plays a pivotal role in the pathogenesis of intraocular inflammation , which has been borne out in the treatment of adult uveitis . In mouse models of anterior uveitis, deleting the p55 receptor, as well as combined TNF receptor (TNFR) p55- and p75-knockout animals, resulted in reduced disease  more significantly than the effect of TNFR p55 fusion protein . "
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ABSTRACT: Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in children. Children with JIA are at risk of inflammation of the uvea in the eye (uveitis). Overall, 20% to 25% of paediatric uveitis is associated with JIA. Major risk factors for development of uveitis in JIA are oligoarticular pattern of arthritis, an age at onset of arthritis of less than seven years of age, and antinuclear antibody positivity. In the initial stages of mild to moderate inflammation the uveitis is asymptomatic. This has led to current practice of screening all children with JIA for uveitis. Approximately 12% to 38% of patients with JIA develop uveitis in seven years following onset of arthritis. In 30% to 50% of children with JIA-associated uveitis structural complications are present at diagnosis. Furthermore about 50% to 75% of those with severe uveitis will eventually develop visual impairment secondary to ocular complications such as cataract and glaucoma. Defining the severity of inflammation and structural complications in uveitis patients is now possible following Standardised Uveitis Nomenclature (SUN) guidelines, and modified to incorporate the consensus of end point and outcome criteria into the design of randomised trials. Despite current screening and therapeutic options (pre-biologics) 10% to 15% of children with JIA-associated uveitis may develop bilateral visual impairment and certified legally blind. To date, there remains no controlled trial evidence of benefits of biologic therapy.Methods/design: This study will randomise 154 patients aged 2 to 18 years with active JIA-associated uveitis (despite methotrexate (MTX) treatment for at least 12 weeks). All participants will be treated for 18 months, with follow up of 3 years from randomisation (continuing on MTX throughout). All participants will receive a stable dose of MTX and in addition either adalimumab (20 mg/0.8 ml for patients <30 kg or 40 mg/0.8 ml for patients weighing 30 kg or more, subcutaneous (s/c) injection every 2 weeks based on body weight), or placebo (0.8 ml as appropriate according to body weight) s/c injection every 2 weeks.
This is the first randomised controlled trial that will assess the clinical effectiveness, safety and cost effectiveness of adalimumab in combination with methotrexate for the treatment of juvenile idiopathic arthritis associated uveitis.Trial registration: ISRCTN10065623.
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