Functionally Distinct IFNγ+ IL-17A+ Th cells in experimental autoimmune uveitis: T cell heterogeneity, migration and steroid response.

Immunopathogenic roles for both Th1 (CD4+ IFNγ+ ) and Th17 (CD4+ IL-17A+ ) cells have been demonstrated in experimental autoimmune uveitis (EAU). However, the role for Th17/Th1 (CD4+ T cells co-expressing IFNγ and IL-17A) cells in EAU is not yet understood. Using interphotoreceptor retinoid-binding protein (IRBP) peptide-induced EAU in mice, we found increased levels of Th17/Th1 cells in EAU retinae (mean 9.6 ± 4.2%) and in dLNs (mean 8.4 ± 3.9%; P = 0.01) relative to controls. Topical dexamethasone treatment effectively reduced EAU severity and decreased retinal Th1 cells (P = 0.01), but had no impact on retinal Th17/Th1 or Th17 cells compared to saline controls. Using in vitro migration assays with mouse CNS endothelium we demonstrated that Th17/Th1 cells were significantly increased within the migrated population relative to controls (mean 15.6 ± 9.5% vs. 1.9 ± 1.5%; P = 0.01). Chemokine receptor profiles of Th17/Th1 cells (CXCR3 and CCR6) did not change throughout the transendothelial migration process and were unaffected by dexamethasone treatment. These findings support a role for Th17/Th1 cells in EAU and their resistance to steroid inhibition suggests the importance of targeting both Th17 and Th17/Th1 cells for improving therapy. This article is protected by copyright. All rights reserved.