Aspirin gained tremendous popularity during the 1918 Spanish Influenza virus pandemic, 50 years prior to the demonstration of their inhibitory action on prostaglandins. Here, we show that during influenza A virus (IAV) infection, prostaglandin E2 (PGE2) was upregulated, which led to the inhibition of type I interferon (IFN) production and apoptosis in macrophages, thereby causing an increase in virus replication. This inhibitory role of PGE2 was not limited to innate immunity, because both antigen presentation and T cell mediated immunity were also suppressed. Targeted PGE2 suppression via genetic ablation of microsomal prostaglandin E-synthase 1 (mPGES-1) or by the pharmacological inhibition of PGE2 receptors EP2 and EP4 substantially improved survival against lethal IAV infection whereas PGE2 administration reversed this phenotype. These data demonstrate that the mPGES-1-PGE2 pathway is targeted by IAV to evade host type I IFN-dependent antiviral immunity. We propose that specific inhibition of PGE2 signaling might serve as a treatment for IAV.

Mechanisms by which regulatory T (Treg) cells fail to control inflammation in asthma remain poorly understood. We show that a severe asthma-associated polymorphism in the interleukin-4 receptor alpha chain (IL4RA R576) promotes conversion of induced Treg (iTreg) cells towards a T helper 17 (TH17) cell fate. This skewing is mediated by the recruitment by IL-4Rα-R576 of the growth factor receptor-bound protein 2 (GRB2) adaptor protein, which drives IL-17 expression by activating a pathway involving extracellular signal-regulated kinase, IL-6 and STAT3. Treg cell-specific deletion of Il6ra or Rorc, but not Il4 or Il13, prevented exacerbated airway inflammation in Il4raR576 mice. Furthermore, treatment of Il4raR576 mice with a neutralizing anti-IL-6 antibody prevented iTreg cell reprogramming into TH17-like cells and protected against severe airway inflammation. These findings identify a novel mechanism for the development of mixed TH2-TH17 cell inflammation in genetically prone individuals, and point to interventions that stabilize iTreg cells as potentially effective therapeutic strategies.

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Elucidating the mechanisms that sustain asthmatic inflammation is critical for precision therapies. We found that IL-6 and STAT3 transcription factor-dependent upregulation of Notch4 receptor on Iung tissue regulatory T (T reg ) cells is necessary for allergens and particulate matter pollutants to promote airway inflammation. Notch4 subverted T reg cells into T H 2 and T H 17 effector T (T eff ) cells by Wnt and Hippo pathway-dependent mechanisms. Wnt activation induced growth and differentiation factor 15 (GDF15) expression in T reg cells, which activated group 2 innate lymphoid cells (ILC2) to provide a feed-forward mechanism for aggravated inflammation. Notch4, Wnt and Hippo were upregulated on circulating T reg cells of asthmatics as a function of disease severity, in association with reduced T reg cell-mediated suppression. Our studies thus identify Notch4-mediated immune tolerance subversion as a fundamental mechanism that licenses tissue inflammation in asthma.

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Intravenous immunoglobulin (IVIg) is a polyclonal immunoglobulin G preparation with potent immunomodulatory properties. The mode of action of IVIg has been investigated in multiple disease states, with various mechanisms described to account for its benefits. Recent data indicate that IVIg increases both the number and the suppressive capacity of regulatory T cells, a subpopulation of T cells that are essential for immune homeostasis. IVIg alters dendritic cell function, cytokine and chemokine networks, and T lymphocytes, leading to development of regulatory T cells. The ability of IVIg to influence Treg induction has been shown both in animal models and in human diseases. In this review, we discuss data on the potential mechanisms contributing to the interaction between IVIg and the regulatory T-cell compartment.

The use of tocilizumab in two children with severe persistent, steroid-resistant asthma resulted in immunological improvement and suggestive of clinical improvement.

IVIG was effective in ameliorating allergic airway disease in our model. IVIG may be a promising adjunct therapy requiring further study for patients with severe asthma.