Potential adjuvant effect of intranasal urban aerosols in mice through induction of dendritic cell maturation

Urban air pollution is a crucial environmental problem in industrialized and developing countries. Although epidemiologic studies have associated exposure to urban aerosols with exacerbations of allergic airway diseases, the underlying mechanism of toxicity is largely unknown. Here, we evaluated the effect of urban aerosols from China, on the induction of allergic diseases in vivo and on the function of dendritic cells (DCs) in vitro. Mice were intranasally given urban aerosol plus ovalbumin (OVA), and the levels of OVA-specific antibodies in the plasma were determined. Urban aerosol induced higher OVA-specific immunoglobulin (Ig) G and IgE responses than OVA alone. Furthermore, urban aerosol plus OVA induced high levels of histamine production, indicating that exposure to the aerosol could cause serious allergic symptoms. Next, we examined the effect of urban aerosol on DCs. The aerosol enhanced cell-surface expression of co-stimulatory molecules such as CD80 and CD86 and the production of interleukin (IL)-1β and IL-6 on DCs. In addition, allogeneic T-cell-stimulation assay showed that the urban aerosol could activate T cells through maturation of DCs. These results indicate that urban aerosols can induce allergic airway diseases through activation of DCs.