Dendritic cells are associated with augmentation of antigen sensitization by influenza A virus infection in mice

To study the mechanisms responsible for enhanced sensitization of inhaled antigen in respiratory viral infections, we examined the contribution of dendritic cells (DC) and T lymphocytes to the development of inhalation sensitization during infection with influenza A virus in mice. BALB/c mice were sensitized by inhalation of ovalbumin (OA) from 3 to 7 days after the inoculation with influenza A virus, and were challenged with OA 3 weeks later. Airway responsiveness and serum OA-specific IgE were increased. The numbers of eosinophils and CD4(+) and CD8(+) T cells in bronchoalveolar ravage fluid were also increased. These changes were not observed in animals only sensitized with OA or only inoculated with the virus. In animals only inoculated with the virus, DC were immunohistochemically detected on the bronchial epithelium on days 2-5. With OA inhalation after virus inoculation, DC with high expression of MHC class II were retained for 5 weeks. These results show that influenza virus infection induces the migration of DC to the bronchial epithelium, and that simultaneous inhalation of antigen causes the loading of antigen-peptide/class II molecule complex on DC. Thus, the migration of DC in viral infection may play some role in the augmentation of antigen sensitization.