Dual Role of Interleukin-1 alpha in Delayed-Type Hypersensitivity and Airway Hyperresponsiveness

Background: Using a T helper (Th)1/Th2 disease model, we previously showed that genetically determined Th development depends on dendritic cell-derived interleukin (IL)-1 alpha. In Leishmania major infections, Th1 immunity develops if IL-1 alpha is present during T cell priming, whereas at later time points, IL-1 alpha worsens disease outcome. In the present study, we determined the role of IL-1 alpha in other Th2-mediated diseases. Methods: BALB/c mice were subjected to delayedtype hypersensitivity (DTH) or ovalbumin (OVA)/alum-induced allergic asthma in the presence or absence of IL-1 alpha. Results: In DTH, mice treated with IL-1 alpha during sensitization with keyhole limpet hemocyanin (KLH)/alum developed decreased footpad swelling associated with elevated KLH-specific interferon-alpha levels. In asthma, significantly decreased airway hypersensitivity responses (AHRs) were detected upon treatment with IL-1 alpha during T cell priming. In contrast to control mice, IL-1 alpha-treated mice showed reduced peribronchial inflammatory infiltrates. The bronchoalveolar lavage (BAL) fluid contained significantly decreased eosinophil numbers (approximately 50%), but 4 times more neutrophils. The BAL fluid of IL-1 alpha-treated BALB/c exhibited reduced amounts of IL-5 and OVA-specific IgE serum levels. In contrast, IL-1 alpha treatment at later time points after sensitization or during allergen challenge worsened AHR, had no effect on lung inflammation and BAL fluid cell composition. Furthermore, cytokine levels (IL-5, IL-13) and antigen-specific IgE were increased or unaltered under these conditions. Conclusion: Similarly to leishmaniasis, IL-1 alpha administration during sensitization of Th2-mediated allergic reactions suppresses the course of disease by shifting the immune response towards Th1, whereas later treatments worsen disease outcome. Future studies will elucidate the therapeutic value of IL-1 alpha in asthmatic patients. Copyright (C) 2010 S. Karger AG, Basel