Self-Sustained Resistance to Suppression of CD8+ Teff Cells at the Site of Autoimmune Inflammation Can Be Reversed by Tumor Necrosis Factor and Interferon-γ Blockade

Abstract

OBJECTIVE: Resistance of effector T cells (Teff) to regulatory T cell (Treg)-mediated suppression contributes to the breakdown of peripheral tolerance in the inflamed joints of Juvenile Idiopathic Arthritis (JIA) patients. However, an unanswered question is whether this resistant phenotype is self-sustained and whether CD8(+) and CD4(+) Teff share the same mechanism of resistance to suppression. Here, we investigated CD8(+) Teff intrinsic resistance to suppression and how this can be targeted therapeutically. METHODS: CD8(+) or CD4(+) Teff were cultured with or without antigen presenting cells (APC) in Treg-dependent and -independent suppression assays. Synovial fluid (SF)-derived Teff were cross-cultured with peripheral blood (PB) Treg from JIA patients or healthy controls. TNF-α or IFN-γ blocking agents were used to restore Teff responsiveness to suppression. RESULTS: Suppression of cell proliferation and cytokine production by CD8(+) Teff from the SF of JIA patients was severely impaired compared to PB of JIA patients, regardless of APC and CD4(+) Teff cell presence. Similarly to CD4(+) Teff, impaired suppression of CD8(+) Teff was shown to be an intrinsic feature of this cell population. Whereas TNF-α blockade rescued both CD8(+) and CD4(+) Teff resistance, autocrine release of IFN-γ selectively sustained CD8(+) Teff resistance, which could be relieved by IFN-γ blockade. CONCLUSION: Unlike CD4(+) Teff, resistance of CD8(+) Teff to suppression at the site of autoimmune inflammation is maintained by autocrine release of IFN-γ and blockade of IFN-γ restores CD8(+) Teff responsiveness to suppression. These findings indicate a potential therapeutic value of blocking IFN-γ to restore immune regulation in JIA. This article is protected by copyright. All rights reserved.