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David A. Copland, Lauren P. Schewitz-Bowers, Andrew D. Dick, Richard W. Lee; Th17 Cells Are Refractory To Dexamethasone But Sensitive To Cyclosporine A. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4167.
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We have previously reported that CD4+ cells from patients with steroid refractory (SR) uveitis have a greater propensity to generate IL-17 following TCR ligation than steroid sensitive (SS) controls, and that Th17 cells derived from SR patients have a restricted genome-wide response to the synthetic glucocorticoid dexamethasone (Dex). Calcineurin inhibitors such as cyclosporine A (CsA) are commonly used in clinical practice to rescue SR uveitis, and the purpose of this study was to test the hypothesis that Th17 cells are SR but CsA-sensitive, both in vitro and in vivo.
In vitro: CD4+ cells from OT-II mice were cultured with ovalbumin and either Th1 (IL-12, αIL-4) or Th17 (IL-6, IL-1α, TGF-β, αIFN-γ, αIL-4, αIL-12) polarising cytokines. After activation, polarised cells were phenotyped for IL-17 and IFN-γ expression and incubated with either Dex or CsA to evaluate proliferative responses. In vivo: B10.RIII mice were immunised for EAU, and clinical disease monitored using Topical Endoscopic Fundal Imaging (TEFI). Mice displaying early signs of disease onset (raised optic nerve or early vasculitis) were selected for treatment with 10mg/kg Dex, 5mg/kg CsA or left untreated. Animals were treated every other day and after 4 treatments were sacrificed, their eyes enucleated, and the retina was analysed by flow cytometry to determine the cellular infiltrate phenotype.
Peptide specific Th17 cell proliferation was suppressed in the presence of CsA, but not with Dex (85% vs. 6%) whereas suppression of Th1 cell proliferation was greatest with Dex compared to CsA (99% vs. 44%). In vivo, clinical disease was suppressed in both groups, but Dex treated mice showed the greatest reduction in disease severity observed by TEFI. However, reductions in retinal CD4+ and CD11b+ infiltrate were similar between the Dex vs. CsA treatment groups compared to control animals (CD4+: 81% & 74%; CD11b+: 59% & 54%). Analysis of CD4+ cytokine expression demonstrates that Dex reduces IFN-γ expression with maintained IL-17 production, whilst CsA results in reduced IL-17 expression with maintained IFN-γ production.
Th17 cells are refractory to glucocorticoid inhibition with Dex, but sensitive to calcineurin inhibition with CsA, both in vitro and in vivo. This is consistent with the Th17 bias observed in SR patients, revealing a mechanism for the success of CsA treatment in SR uveitis and provides a rationale for targeted calcineurin inhibition in the treatment of Th17 driven autoimmune diseases.
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