Interferon gamma boosts the nucleotide oligomerization domain 2-mediated signaling pathway in human dendritic cells in an X-linked inhibitor of apoptosis protein and mammalian target of rapamycin-dependent manner

Interferon-γ Stimulates Interleukin-27 Derived from Dendritic Cells to Regulate Th9 Differentiation through STAT1/3 Pathway

The initiation and progression of allergic asthma (AA) are associated with complex interactions between inflammation and immune response. Herein, we report the specific mechanisms underlying the molecular action of interferon (IFN)-γ in AA regulation. We speculated that IFN-γ inhibits Th9 differentiation by regulating the secretion of interleukin (IL)-27 from dendritic cells (DCs), thereby suppressing airway inflammation in asthma. We constructed a mouse model of ovalbumin-induced AA and overexpressed IFN-γ to evaluate the effect on the IL-27/Th9 axis via the in vitro effect of IFN-γ on IL-27 secretion by DCs and their influence on Th9 differentiation and asthmatic inflammation. IFN-γ overexpression reduced the proportion of Th9 cells and DCs and altered lung morphology and cytokine production in AA-induced mice, thus suppressing the AA phenotype. In addition, exogenous IFN-γ stimulation promoted the secretion of IL-27 and suppressed Th9 differentiation of CD4+ T cells via signal transducer and activator of transcription 1/3 (STAT1/3) signaling in a time-dependent manner. This study aimed to clarify the regulatory effect and mechanism of the IFN-γ/DCs/IL-27/Th9 axis on AA and provide novel insights for effective targeted treatment of asthma.

A regulatory region on RIPK2 is required for XIAP binding and NOD signaling activity

Signaling via the intracellular pathogen receptors nucleotide-binding oligomerization domain-containing proteins NOD1 and NOD2 requires receptor interacting kinase 2 (RIPK2), an adaptor kinase that can be targeted for the treatment of various inflammatory diseases. However, the molecular mechanisms of how RIPK2 contributes to NOD signaling are not completely understood. We generated FLAG-tagged RIPK2 knock-in mice using CRISPR/Cas9 technology to study NOD signaling mechanisms at the endogenous level. Using cells from these mice, we were able to generate a detailed map of post-translational modifications on RIPK2. Similar to other reports, we did not detect ubiquitination of RIPK2 lysine 209 during NOD2 signaling. However, using site-directed mutagenesis we identified a new regulatory region on RIPK2, which dictates the crucial interaction with the E3 ligase XIAP and downstream signaling outcomes.

NOD Signaling and Cell Death

Innate immune signaling and programmed cell death are intimately linked, and many signaling pathways can regulate and induce both, transcription of inflammatory mediators or autonomous cell death. The best-characterized examples for these dual outcomes are members of the TNF superfamily, the inflammasome receptors, and the toll-like receptors. Signaling via the intracellular peptidoglycan receptors NOD1 and NOD2, however, does not appear to follow this trend, despite involving signaling proteins, or proteins with domains that are linked to programmed cell death, such as RIP kinases, inhibitors of apoptosis (IAP) proteins or the CARD domains on NOD1/2. To better understand the connections between NOD signaling and cell death induction, we here review the latest findings on the molecular regulation of signaling downstream of the NOD receptors and explore the links between this immune signaling pathway and the regulation of cell death.

Interleukin-28B dampens airway inflammation through up-regulation of natural killer cell-derived IFN-γ

Interleukin-28A (IL-28A) modulates CD11c+ dendritic cell (DC) function and promotes type 1T helper (Th1) differentiation, thus suppressing allergic airway diseases. However, the function of the IL-28A isoform IL-28B in these diseases remains largely unknown. In this study, we revealed a novel role of IL-28B in inducing type 1 immunity and protecting against ovalbumin (OVA)-induced allergic asthma in mice. IL-28B overexpression in wild-type mice promoted natural killer (NK) cell polarization in the lung, leading to the increased number of interferon (IFN)-γ-producing NK1 cells as well as Th1 differentiation. Importantly, IL-28B overexpression had no protective effect on OVA-induced asthma in IFN-γ-knockout (IFN-γ−/−) mice. These results demonstrate that IL-28B ameliorates experimental allergic asthma via enhancing NK cell polarization, which might be useful for prevention and treatment of allergic asthma.

How genetic testing can lead to targeted management of XIAP deficiency-related inflammatory bowel disease

X-linked lymphoproliferative disease type 2 (XLP-2, OMIM 300635) is a primary immunodeficiency caused by the loss of X chromosome-linked inhibitor of apoptosis (XIAP), the X-linked inhibitor of apoptosis gene at Xq25. XLP-2 individuals are susceptible to several specific and potentially fatal infections, such as Epstein-Barr virus (EBV). Children with XIAP-related XLP-2 may present with either familial hemophagocytic lymphohistiocytosis, often triggered in response to EBV infection, or with a treatment-refractory severe pediatric form of inflammatory bowel disease (IBD) that might be diagnosed as Crohn disease. However, this monogenic cause of IBD is distinct from adult Crohn disease (a polygenic and multifactorial disease) in its etiology and responsiveness to therapy. XLP-2 and the associated IBD symptoms are managed by a reduced-intensity conditioning regimen with an allogeneic hematopoietic stem cell transplantation that causes resolution of gastrointestinal symptoms. Exome sequencing has enabled identification of XIAP-deficient diseased individuals and has altered their morbidity by providing potentially lifesaving strategies in a timely and effective manner. Here, we summarize XLP-2 IBD treatment history and patient morbidity/mortality since its original identification in 2006. Since XLP-2 is rare, cases are probably undergiagnosed or misdiagnosed. Consideration of XLP-2 in children with severe symptoms of IBD can prevent serious morbidities and mortality, avoid unnecessary procedures, and expedite specific targeted therapy.Genet Med 19 2, 133-143.