Therapeutic expansion of CD4+FoxP3+ regulatory T cells limits allergic airway inflammation during pulmonary fungal infection

Allergic asthma can be frequently caused and exacerbated by sensitization to ubiquitous fungal allergens associated with pulmonary mucus production, airway hyperresponsiveness and bronchial constriction, resulting in a complex disease that is often difficult to treat. Fungal infections are frequently complicated by the development of a type 2 immune response that prevents successful elimination of the fungal pathogen. Furthermore, production of type 2 cytokines triggers allergic airway inflammation. Following intranasal infection of BALB/c mice with the fungus Cryptococcus neoformans , we recently described a more pronounced type 2 immune response in the absence of regulatory T (Treg) cells. To determine whether Treg cell expansion is able to suppress type 2-related fungal allergic inflammation, we increased Treg cell numbers during pulmonary C. neoformans infection by administration of an interleukin (IL)-2/anti-IL-2 complex. Expansion of Treg cells resulted in reduced immunoglobulin (Ig) E production and decreased allergic airway inflammation including reduced production of pulmonary mucus and type 2 cytokines as well as production of immunosuppressive cytokines such as IL-10 and transforming growth factor (TGF)-β1. From our data we conclude that Treg cells and/or their suppressive mediators represent potential targets for therapeutic intervention during allergic fungal airway disease.