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Kathryn Paunicka, Jerry Y. Niederkorn, Peter W. Chen; CD8+ T Regulatory Cells Require IFN- to Mediate Anterior Chamber-Associated Immune Deviation (ACAID) Suppression. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2261.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction of alloantigens into the anterior chamber (AC) induces a unique form of tolerance known as anterior chamber-associated immune deviation (ACAID), which contributes to the maintenance of ocular immune privilege. Depletion of interferon-gamma (IFN-γ) prevents the expression of ACAID by impairing the suppressive function of ACAID CD8+ T regulatory cells (Tregs). This study examined the role of IFN-γ in the suppressive function of ACAID CD8+ T regulatory cells.
The effect of IFN-γ on alloantigen-induced ACAID was evaluated by injecting BALB/c spleen cells into the AC of WT C57BL/6, IFN-γ-/- C57BL/6 mice, or anti-IFN-γ treated WT C57BL/6 mice. Seven days later, mice were subcutaneously immunized with BALB/c splenocytes. Mice were ear challenged 7 days post immunization in a delayed type hypersensitivity (DTH) assay and ear swelling was measured 24 hrs later. Local Adoptive Transfer (LAT) assays using APCs, CD4+ T effector cells from C57BL/6 mice immunized towards BALB/c alloantigens, and IFN-γ competent, IFN-γ-deficient, or IFN-γR-deficient CD8+ ACAID-induced Tregs were used to evaluate ACAID CD8+ Treg suppressive function in response to IFN-γ.
As expected, WT mice that received AC injections of alloantigen prior to immunization showed suppression of DTH responses compared to control mice. However, IFN-γ-/- mice or mice treated with anti-IFN-γ antibody prior to AC injection of alloantigen failed to develop ACAID and as a result, expressed normal DTH responses. However, CD8+ T cells isolated from IFN-γ-/- mice that were primed in the AC with alloantigens were able to suppress DTH when used in a LAT assay in which exogenous IFN-γ was present. This suggested that IFN-γ was not needed for the induction of CD8+ ACAID T regs, but was required for their suppressive function. This was confirmed in experiments in which CD8+ Treg from IFN-γR-/- mice that were primed in the AC with alloantigens were not able to suppress alloantigen-specific DTH responses in LAT assays. Moreover, depletion of IFN-γ in LAT assays using cells from WT mice blocked ACAID CD8+ Treg suppression of DTH responses.
IFN-γ is widely viewed as a proinflammatory cytokine. However, these results indicate that although IFN-γ is not needed for the induction of CD8+ ACAID Tregs, it is required for ACAID Tregs to exert their suppression of allospecific DTH responses.
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