Cypress pollen causes respiratory syndromes with different grades of severity, including asthma. IL-33, its receptor ST2, and dendritic cells (DCs) have been implicated in human respiratory allergy.

We sought to define a new mouse model of allergy to cypress pollen that recapitulates clinical parameters in allergic patients and to evaluate the implications of DCs and the IL-33/ST2 pathway in this pathology.

BALB/c mice, either wild-type or ST2 deficient (ST2^−/−), were sensitized and challenged with the Cupressus arizonica major allergen nCup a 1. Local and systemic allergic responses were evaluated. Pulmonary cells were characterized by means of flow cytometry. DCs were stimulated with nCup a 1 and tested for their biological response to IL-33 in coculture assays.

nCup a 1 causes a respiratory syndrome closely resembling human pollinosis in BALB/c mice. nCup a 1–treated mice exhibit the hallmarks of allergic pathology associated with pulmonary infiltration of eosinophils, T cells, and DCs and a dominant T_H2-type immune response. IL-33 levels were increased in lungs and sera of nCup a 1–treated mice and in subjects with cypress allergy. The allergen-specific reaction was markedly reduced in ST2^−/− mice, which showed fewer infiltrating eosinophils, T cells, and DCs in the lungs. Finally, stimulation of DCs with nCup a 1 resulted in ST2 upregulation that endowed DCs with increased ability to respond to IL-33–mediated differentiation of IL-5– and IL-13–producing CD4 T cells.

Our findings define a novel preclinical model of allergy to cypress pollen and provide the first evidence of a functionally relevant linkage between pollen allergens and T_H2-polarizing activity by DCs through IL-33/ST2.