Natural antibodies drive type 2 immunity in response to damage associated molecular patterns.

Allergic Airway Disease (AAD) is an example of type 2 inflammation which leads to chronic airway eosinophilia controlled by CD4 Th2 cells. Inflammation is reinforced by mast cells and basophils armed with allergen-specific IgE made by allergen-specific B2 B cells of the adaptive immune system. Little is known about how AAD is affected by innate B1 cells which produce natural antibodies (NAbs) that facilitate apoptotic cell clearance and detect damage and pathogen associated molecular patterns (DAMPS and PAMPS). We used transgenic mouse models lacking either B cells or NAbs in distinct mouse models of AAD, that require either DAMPS or PAMPS as the initial trigger for type 2 immunity. In a DAMP-induced allergic model, driven by alum and uric acid, mouse strains lacking B cells (CD19DTA), NAbs (IgHEL MD4), or all secreted antibodies (sIgm-/-Aid-/-), displayed significant reduction in both eosinophilia and Th2 priming compared to wild-type or Aid-/- mice lacking only germinal center dependent high-affinity class switched antibodies. Replenishing B-cell deficient mice with either unimmunized B1 B cells or NAbs during sensitization restored eosinophilia, suggesting NAbs are required for licensing antigen presenting cells to prime type 2 immunity. Conversely, PAMP-dependent type 2 priming to house dust mite or Aspergillus were not dependent on NAbs. This study reveals an underappreciated role of B1 B cell-generated natural antibodies in selectively driving DAMP-induced type-2 immunity.