Fig. 4.

Generation of CD4⁺ and CD8⁺ lung-resident memory T (T_RM) cells in lung tissues. At 30 days post-3rd immunization in Study 1, single-cell suspensions from the lung samples were collected and subjected to FACS to determine the percentages of CD4⁺CD44⁺CD69⁺ (A), CD4⁺ CD44⁺CD69⁺CD103⁺ (B), CD4⁺ CD44⁺CD69⁺CD103⁻ (C), CD8⁺CD44⁺CD69⁺ (D), CD4⁺ CD44⁺CD69⁺CD103⁺ (E) and CD8⁺ CD44⁺CD69⁺CD103⁻ (F) T_RM cells (n = 4, *P < 0.05, **P < 0.01, ***P < 0.001). Notably, Salmonella strain χ11802 harboring plasmids pYL180 and pYL230 was designated S180 and S230, respectively. Two oral immunizations with S180 and S230 followed by the 3rd intranasal boost immunization with purified nanoparticles were named S180in and S230in, respectively