Additionally, unsensitized mice receiving three days of ryegrass only developed modest airway eosinophilia and neutrophilia. cell (ILC2) and Th2 cell recruitment to the airway was improved afterAlternariaextract exposure in ryegrass challenged mice. Innate challenges withAlternariaextract induced BAL eosinophilia, Th2 cell recruitment as well as ILC2 growth and proliferation. == Conclusions == A single exposure ofAlternariaextract in ryegrass sensitized and challenged mice enhances the type-2 lung inflammatory response including Uridine triphosphate airway eosinophilia, peribronchial infiltrate, and mucus production probably through Th2 cell recruitment and ILC2 growth. If translated to humans, exposures to both grass pollen andAlternariamay be a potential cause of thunderstorm-related asthma. Keywords:Alternaria, asthma, thunderstorm asthma, ryegrass == Intro == The inflammatory response in sensitive asthma has mainly been characterized by a dysregulated adaptive immune response including differentiation of Th2 cells that create IL-4, IL-5, and IL-13 resulting in IgE production, eosinophil infiltration and mucus production in the lungs [1]. Though much has been learned about pathogenic adaptive Th2 cell reactions over the past few decades, recent studies Uridine triphosphate have shown that innate type-2 reactions also contribute to cells eosinophilia and mucus production independent of the presence of adaptive immune cells [2-4]. We recently reported that a solitary administration of the fungal allergen extractAlternaria alternatagiven to unsensitized mice results in airway eosinophilia and improved IL-5 levels and is present in RAG2 deficient mice that lack B and T cells [5,6]. Further, we have demonstrated that IL-5 generating innate lymphoid cells (ILC2) are rapidly activated afterAlternariaextract challenge and contribute to Uridine triphosphate lung eosinophilia [6]. This suggests that the adaptive Th2 paradigm may not completely explain type 2 reactions in asthma and that innate immune activation by allergens such asAlternariamay contribute to eosinophilic airway swelling and mucus production. Though asthma offers many medical, physiologic, and immunologic phenotypes, the majority of asthmatics have Uridine triphosphate allergic triggers. Exposure to the fungal allergenAlternaria alternatais specifically associated with severe asthma including life-threatening exacerbations as well as thunderstorm-related asthma [7-13]. Thunderstorm asthma is definitely a well-documented medical phenomenon in which patients develop severe asthma symptoms in epidemics during a thunderstorm outflow in which pollens and fungi are swept up and concentrated at high levels [14,15]. This prospects to an abundance of allergen including formation of respirable particles of pollen (<10 m) and fragmented fungal spores ofAlternaria alternata[10]. IgE sensitization to grass pollen allergens including ryegrass is definitely a risk element for patients to develop asthma exacerbations during thunderstorms suggesting a link between adaptive Th2 reactions to grass pollen and thunderstorm asthma [16,17]. Little is known about the underlying immune mechanisms in thunderstorm asthma beyond one statement that demonstrated improved sputum eosinophilia and IL-5+ cells in the lungs of symptomatic asthmatics during thunderstorms suggesting a potentiated type 2 response [17]. The medical associations betweenAlternaria, grass pollen exposure and epidemics of severe asthma during thunderstorms are intriguing but how these inhaled allergens might lead to improved airway inflammatory reactions is unclear. We hypothesized that an innate type 2 response induced byAlternariaextract may enhance eosinophilic lung swelling induced by ryegrass pollen. We demonstrate that a solitary challenge withAlternariaextract enhances lung eosinophilia, peribronchial infiltration, and epithelial mucus production as well as Th2 cell and ILC2 recruitment in ryegrass challenged WT mice. Our data suggests that the combination of innate and adaptive reactions to allergens may contribute to severe asthma. == Materials and Methods == == Mice == Female BALB/c mice (The Jackson Laboratory, Bar Harbor, ME) were used at 810 wk of age. All animal experimental procedures were authorized by the University or college of California, San Diego Animal Subjects Committee. == Ryegrass and Alternaria airway swelling models == To induce airway swelling with ryegrass pollen, mice were immunized intraperitoneally with 200 g of ryegrass pollen draw out (Lolium perenne, Uridine triphosphate Lot 147138, Greer, Lenoir, NC) adsorbed to 2 mg of an aqueous answer of alum hydroxide (Aldrich) in 500 l PBS or in PBS without alum on days 0 and 7. Intranasal ryegrass pollen (100 g in 40L in PBS, LPS content material .71 ng/ml by Lonza limulus assay) was administered for three consecutive days under isoflurane anesthesia. IntranasalAlternaria alternataextract (Lot 177372, Greer) was given at a dose of 25 or 50 g in 40 L of PBS 3 days prior or 3 days after rye grass challenges. In some experiments BAL and lungs CD109 from mice were analyzed 3 days afterAlternariaextract or PBS difficulties. In other experiments, nave mice were given 100 g of ryegrass draw out intranasally daily for three days and euthanized one day later on. Control challenges consisted of the same volume of PBS.