Fig. 6

Nanoparticles traffic the nasal epithelium to induce immune responses. Nanoparticles can cross the mucosal respiratory layer to reach the nasal epithelial tissues through microfold cells (M cells). The M cells are antigen-delivering epithelial cells that transport antigens by transcytosis to the underlying immune cells. Nanoparticles can also be actively captured by dendritic cells or transmitted passively through epithelial cell junctions. Cells that have encountered nanoparticles migrate to the lymph nodes and activate T helper cells. Activated T helper cells induce B cell proliferation in the lymph nodes (B cell zone) and enter the systemic circulation to reach the site of inflammation. Among class-switched B cells, IgA + B cells differentiate into antibody-secreting plasma cells to produce IgA dimers. IgA dimers are transferred to the mucosal surface by the polymeric immunoglobulin receptor that translocates the secreted IgA across the epithelium