Nanoparticle size influences the magnitude and quality of mucosal immune responses after intranasal immunization

► We determined how nanoparticle size modulates mucosal immunity in mice. ► Two sizes 200 and 30 nm nanoparticles were compared after intranasal immunization. ► 200 nm nanoparticles enhanced lung antigen-specific CD4+ T cell immunity. ► 200 nm nanoparticles increased IFNγ production by CD4+ T cells on a per-cell basis. ► 200 nm nanoparticles increased both systemic and mucosal antibody responses.