Interferon-gamma ameliorates experimental autoimmune encephalomyelitis by inducing homeostatic adaptation of microglia

Compelling evidence has shown that interferon (IFN)-γ has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-γ may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-γ at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-γ administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b⁺ myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from the spinal cord of IFN-γ-treated EAE mice that were ex vivo re-stimulated with a low dose (1 ng/ml) of IFN-γ and neuroantigen, promoted a significantly higher induction of CD4⁺ regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-β secretion. Additionally, IFN-γ-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-γ-treated EAE mice had a significantly higher frequency of CX3CR1^high MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1^highPD-L1^lowCD11b⁺Ly6G^- cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1^highPD-L1^low MG). Amelioration of clinical symptoms and induction of CX3CR1^highPD-L1^low MG by IFN-γ were dependent on STAT-1. RNA-seq analyses revealed that in vivo treatment with IFN-γ promoted the induction of homeostatic CX3CR1^highPD-L1^low MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-γ plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-γ in EAE.

Decreased Expression of TIM-3 on Th17 Cells Associated with Ophthalmopathy in Patients with Graves' Disease

Purpose:

Thyroid-associated Ophthalmopathy (TAO) is one of the most common orbital immunological diseases in adults. CD4+ helper T (Th) cells play important roles in the pathogenesis of TAO. But the mechanisms regulating CD4+ T cell activity is unclear. This study examines T cell immunoglobulin domain and mucin domain 3 (TIM-3) expression in helper T cell type 1 (Th1), Th17, and regulatory T cells in sufferers of TAO.

Methods:

Participants were divided into 3 groups: patients with TAO, patients with Graves’ disease but without orbitopathy (GD), and healthy control patients (HC). Peripheral blood samples were collected for each patient in the designated group. Flow cytometry methods assessed the frequency of Th1 (CD4+IFN-γ+), Th17 (CD4+IL-17+), regulatory T cells (CD4+CD25hiCD127lo), and TIM-3 protein expression. Mean fluorescence intensity (MFI) measured the magnitude of TIM-3 expression and the percentage of TIM-3+ cells for each patient.

Results:

Compared to the GD group, TAO patients possessed higher frequencies of Th1 and Th17 cells in peripheral blood samples. The percentage of TIM-3+ Th1 and Th17 cells was significantly lower in the TAO patients than the GD group. Across all patients sampled, TIM-3+ cell percentage negatively correlated with Th1 cell frequency. Th1 and Th17 cells exhibited significantly decreased expression of TIM-3 in TAO patients compared to healthy controls. Regulatory T cells showed little TIM-3 expression and we observed no significant differences in frequency between groups.

Conclusion:

These results suggest a role for TIM-3 in the regulation of Th1 and Th17 cells and the pathogenesis of Graves’ ophthalmopathy.