Interplay between bacteria and pulmonary immune system in respiratory infections

The local immune system of the lungs is essential for the defense against pathogens, and respiratory bacterial infections remain a major cause of mortality in patients with lower respiratory tract diseases. However, the precise mechanisms underlying immune–pathogen interactions and the modulatory roles of commensal bacteria remain incompletely understood. This review discusses the mechanisms of immune recognition and inflammatory responses during bacterial respiratory bacterial infections, highlighting the importance of pattern recognition receptors, including toll-like receptors, nucleotide oligomerization domain-like receptors, and C-type lectin receptors in detecting pathogens and triggering immune signaling pathways. We also explore how commensal bacteria influence the respiratory immune microenvironment and discuss the complex interplay among pathogenic bacteria, commensals, and the host pulmonary immune system. This analysis provides a theoretical foundation for the development of targeted therapeutics against bacterial respiratory infections.