Allergens Abrogate the Anti-inflammatory Property of DNA and Unmasks Macrophage/ILC2-STING-TNFα-driven Neutrophilic Asthma

The mechanism of neutrophilic and mixed neutrophilic-eosinophilic asthma is poorly understood. We found that extracellular DNA and nucleosomes (Nucs) were elevated in the airways from neutrophilic-eosinophilic asthma patients and correlated with bronchoalveolar lavage neutrophils. Bronchial tissue from neutrophilic-eosinophilic asthma expressed increased DNA sensor-positive cells. Intranasally administered DNA did not induce airway hyperreactivity (AHR) or any pathology but induced AHR and neutrophilic-eosinophilic inflammation when co- administered with the allergen Alternaria (Alt). Nucs alone induced anti-inflammatory/defensive genes whereas the Nuc-Alt combo increased TNFα and innate cytokines. The Alt-Nuc phenotype was abolished in cGas-/- , Alr-/- , Sting-/- , LysMcre:Stingf/f, Il7rcre:Roraf/f and Tnfrsf1b-/- mice. Alt, unexpectedly, played an essential role in the Nuc-induced phenotype. It abrogated Nuc-induction of anti_x0002_inflammatory genes, facilitated Nuc uptake, induced ILC2s, which, in presence of Nucs, produced high levels of TNFα and promoted neutrophilic infiltration. We established a paradigm where allergens inhibit the anti-inflammatory effects of DNA/Nucs and facilitate STING-TNFα-driven neutrophilic-eosinophilic inflammation in asthma.