Project description:Ocular immune privilege (IP) limits immune surveillance of intraocular tumors as certain immunogenic tumor cell lines (P815, E.G7-OVA) that are rejected when transplanted in the skin grow progressively when placed in the anterior chamber (a.c.) of the eye. As splenectomy (SPLNX) is known to terminate ocular IP, we characterized immune mechanisms responsible for spontaneous rejection of intraocular tumors in SPLNX mice as a first step toward identifying how to restore tumoricidal activity within the eye. Microarray data showed a 3-fold increase in interferon (IFN)-γ and a 2.7-fold increase in Fas ligand (FasL). There was a robust increase in transcripts (127 of 408 surveyed) from interferon (IFN)-stimulated genes and a marked decrease (in 40 of 192 surveyed) in the expression of cell-cycle-associated genes. Non-microarray data confirmed that IFNγ, FasL and CD8+ T cells but not perforin or TNFα were required for elimination of intraocular E.G7-OVA tumors that culminated in destruction of the eye (ocular phthsis). IFNγ and FasL did not target tumor cells directly as the majority of SPLNX IFNγR1-/- mice and Fas-defective lpr mice failed to eliminate ocular E.G7-OVA tumors that expressed Fas and IFNγR1. Bone marrow chimeras showed that immune cell expression of IFNγR1 and Fas was critical and that SPLNX increased the frequency of activated macrophages within ocular tumors in an IFNγ- and Fas/FasL-dependent manner. Rejection of intraocular tumors was associated with increased ocular mRNA expression of several inflammatory genes including FasL, NOS2, CXCL2 and T-bet. Our data support a model in which IFNγ- and Fas/FasL-dependent activation of intratumoral macrophage by CD8+ T cells promotes severe intraocular inflammation that indirectly eliminates intraocular tumors by inducing phthisis. The immunosuppressive mechanisms which maintain ocular IP likely interfere with the interaction between CD8+ T cells and macrophage to limit immunosurveillance of intraocular tumors. C57BL/6 mice that were splenectomized (Tumor_splnx) or were not surgically manipulated (Tumor_intact) were challenged with 10^4 luciferase-expressing E.G7-OVA cells injected into the anterior chamber of the eye. Fifteen days later, the animals were euthanized and tumor-bearing eyes were removed.

Project description:COVID-19 has rapidly circulated around the globe and caused significant morbidity and mortality. The disease is characterized by excessive production of pro-inflammatory cytokines and acute lung damage and patient mortality. Although initial cytokine cascades may be beneficial to the host for clearing the virus, enhanced production of pro-inflammatory cytokines and increasing levels in the systemic circulation, referred to as cytokine storm, can promote tissue damage by inducing inflammatory cell death in both infected and bystander cells. Of the multiple inflammatory cytokines produced by innate immune cells during SARS-CoV-2 infection, we found that the combination of TNF-α and IFN-γ specifically induced cell death characterized by GSDME¬–mediated pyroptosis, caspase-8–mediated apoptosis, and MLKL–mediated necroptosis. Cells deficient in both RIPK3 and caspase-8 or RIPK3 and FADD were resistant to this cell death. However, deletion of pyroptosis, apoptosis, or necroptosis individually was not sufficient to protect against cell death. Mechanistically, the STAT1/IRF1 axis activated by TNF-α and IFN-γ co-treatment induced iNOS for the production of nitric oxide. Pharmacological and genetic deletion of this pathway inhibited pyroptosis, apoptosis, and necroptosis in macrophages. Moreover, inhibition of inflammatory cell death protected mice from TNF-α and IFN-γ–induced lethal cytokine shock that mirrors the pathological symptoms of COVID-19. To determine the physiological relevance of protection, we neutralized both TNF-α and IFN-γ in multiple disease models associated with cytokine storm and found that this treatment provided substantial protection against not only SARS-CoV-2 infection, but also sepsis, hemophagocytic lymphohistiocytosis, and cytokine shock models. Collectively, our findings reveal that blocking the COVID-19 cytokine-mediated inflammatory cell death signaling pathway identified in this study may benefit patients with COVID-19 or other cytokine storm-driven syndromes by limiting inflammation and tissue damage. Additionally, these results open new avenues for the treatment of other infectious and autoinflammatory diseases and cancer where TNF-α and IFN-γ synergism play key pathological roles.

Project description:Ocular immune privilege (IP) limits immune surveillance of intraocular tumors as certain immunogenic tumor cell lines (P815, E.G7-OVA) that are rejected when transplanted in the skin grow progressively when placed in the anterior chamber (a.c.) of the eye. As splenectomy (SPLNX) is known to terminate ocular IP, we characterized immune mechanisms responsible for spontaneous rejection of intraocular tumors in SPLNX mice as a first step toward identifying how to restore tumoricidal activity within the eye. Microarray data showed a 3-fold increase in interferon (IFN)-γ and a 2.7-fold increase in Fas ligand (FasL). There was a robust increase in transcripts (127 of 408 surveyed) from interferon (IFN)-stimulated genes and a marked decrease (in 40 of 192 surveyed) in the expression of cell-cycle-associated genes. Non-microarray data confirmed that IFNγ, FasL and CD8+ T cells but not perforin or TNFα were required for elimination of intraocular E.G7-OVA tumors that culminated in destruction of the eye (ocular phthsis). IFNγ and FasL did not target tumor cells directly as the majority of SPLNX IFNγR1-/- mice and Fas-defective lpr mice failed to eliminate ocular E.G7-OVA tumors that expressed Fas and IFNγR1. Bone marrow chimeras showed that immune cell expression of IFNγR1 and Fas was critical and that SPLNX increased the frequency of activated macrophages within ocular tumors in an IFNγ- and Fas/FasL-dependent manner. Rejection of intraocular tumors was associated with increased ocular mRNA expression of several inflammatory genes including FasL, NOS2, CXCL2 and T-bet. Our data support a model in which IFNγ- and Fas/FasL-dependent activation of intratumoral macrophage by CD8+ T cells promotes severe intraocular inflammation that indirectly eliminates intraocular tumors by inducing phthisis. The immunosuppressive mechanisms which maintain ocular IP likely interfere with the interaction between CD8+ T cells and macrophage to limit immunosurveillance of intraocular tumors.

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Increased Cell Surface Fas Expression is Necessary to Sensitize Lung Fibroblasts to Fas Ligation-Induced Apoptosis: Implications for Fibroblast Accumulation in Idiopathic Pulmonary Fibrosis.

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