and infect epithelial cells via different strategies.

BACKGROUND

As the first line of defense, epithelial cells play a vital role in the initiation and control of both innate and adaptive immunity, which participate in the development of disease. Despite its therapeutic significance, little is understood about the specific interaction between pathogenic microorganisms and lung epithelial cells.

METHODS

In this study, we performed a head-to-head comparison of the virulence and infection mechanisms of () and (), which represent Gram-negative/positive respiratory pathogens, respectively, in lung epithelial cell models for the first time.

RESULTS

Through scanning electron microscopy combined with bacterial infection experiments, we confirmed the ability of and strains to form biofilm and cord factor out of the cell wall. has stronger adhesion and intracellular retention ability, while is more likely to induce acute infection. These pathogens could stay and proliferate in lung epithelial cells and stimulate the secretion of specific cytokines and chemokines through a gene transcription regulator. infection can promote crosstalk among epithelial cells and other immune cells in the lung from a very early stage by prompting the secretion of pro-inflammatory cytokines. Meanwhile, there were significant correlations between infection and higher levels of interleukin-15 (IL-15), interleukin-1Rα (IL-1Rα), fibroblast growth factor (FGF) basic, and granulocyte colony-stimulating factor (G-CSF). At the same time, infection also led to changes in the expression of cytoskeletal proteins in epithelial cells.

CONCLUSIONS

Our results emphasized the immunoprotection and immunomodulation of lung epithelial cells against exogenous pathogenic microorganisms, indicating that different pathogens damaged the host through different strategies and induced varying innate immune responses. At the same time, they provided important clues and key immune factors for dealing with complicated pulmonary infections.