IFN-α Suppresses Myeloid Cytokine Production, Impairing IL-12 Production and the Ability to Support T-Cell Proliferation.

BACKGROUND: Interferon-α (IFN-α) can suppress production of T-cell polarizing cytokines or induce inhibitory antigen-presenting cells that suppress T-cell activation. Previous studies showed that IFN-α therapy fails to boost virus-specific T-cell immunity in patients with chronic hepatitis B virus infection. Our aim was to determine whether IFN-α exposure alters human antigen-presenting cell function in vivo. METHODS: We investigated the immunomodulatory effects using peripheral blood mononuclear cells from healthy donors exposed to IFN-α and chronic hepatitis B (CHB) patients starting IFN-α therapy. RESULTS: IFN-α increased HLA-DR, CD80, CD86, and PD-L1 expression on healthy donor monocytes. In contrast to the activated phenotype, IFN-α inhibited Toll-like receptor-induced cytokine production and monocyte-induced T-cell proliferation. In CHB patients, peg-IFN treatment induced an interferon-stimulated gene signature in monocytes and increased HLA-DR, CD80, CD86, and PD-L1 expression. As early as 3 days after CHB patients started treatment, IFN-α inhibited monocyte cytokine production and T-cell stimulation ex vivo. IFN-α-mediated inhibition of IL-12 production, rather than inhibitory receptor expression, was responsible for inhibition of T-cell proliferation. Addition of IL-12 restored T-cell proliferation to baseline levels. CONCLUSIONS: Understanding how professional antigen-presenting cells respond to immunomodulation is important for both new innate and adaptive-targeted immunotherapies. CLINICAL TRIALS REGISTRATION: NCT00962871.

The Human Male Liver Is Predisposed to Inflammation Via Enhanced Myeloid Responses to Inflammatory Triggers.

Background & Aim: Men have a higher prevalence of liver disease. Liver myeloid cells can regulate tissue inflammation, which drives progression of liver disease. We hypothesized that sex alters the responsiveness of liver myeloid cells, predisposing men to severe liver inflammation. Methods: Luminex was done on plasma from Hepatitis B Virus infected patients undergoing nucleoside analogue cessation in 45 male and female patients. We collected immune cells from the sinusoids of uninfected livers of 53 male and female donors. Multiparametric flow cytometry was used to phenotype and characterize immune composition. Isolated monocytes were stimulated with TLR ligands to measure the inflammatory potential and the expression of regulators of TLR signaling. Results: We confirmed that men experienced more frequent and severe liver damage upon Hepatitis B Virus reactivation, which was associated with inflammatory markers of myeloid activation. No differences were observed in the frequency or phenotype of sinusoidal myeloid cells between male and female livers. However, monocytes from male livers produced more inflammatory cytokines and chemokines in response to TLR stimulation than female monocytes. We investigated negative regulators of TLR signaling and found that TOLLIP was elevated in female liver-derived monocytes. Conclusions: Our data show that enhanced responsiveness of myeloid cells from the male liver predisposes men to inflammation, which was associated with altered expression of negative regulators of TLR signaling.

Type I Interferon Responses Drive Intrahepatic T cells to Promote Metabolic Syndrome.

Obesity-related insulin resistance is driven by low-grade chronic inflammation of metabolic tissues. In the liver, non-alcoholic fatty liver disease (NAFLD) is associated with hepatic insulin resistance and systemic glucose dysregulation. However, the immunological factors supporting these processes are poorly understood. We found that the liver accumulates pathogenic CD8+ T cell subsets which control hepatic insulin sensitivity and gluconeogenesis during diet-induced obesity in mice. In a cohort of human patients, CD8+ T cells represent a dominant intrahepatic immune cell population which links to glucose dysregulation. Accumulation and activation of these cells are largely supported by type I interferon (IFN-I) responses in the liver. Livers from obese mice upregulate critical interferon regulatory factors (IRFs), interferon stimulatory genes (ISGs), and IFNα protein, while IFNαR1-/- mice, or CD8-specific IFNαR1-/- chimeric mice are protected from disease. IFNαR1 inhibitors improve metabolic parameters in mice, while CD8+ T cells and IFN-I responses correlate with NAFLD activity in human patients. Thus, IFN-I responses represent a central immunological axis that governs intrahepatic T cell pathogenicity during metabolic disease.