Innate Immune Responses in Pulmonary Infections

The respiratory tract relies on a multilayered innate defence system to prevent and control infections. The airway epithelium constitutes a physical barrier with mucociliary clearance and secretes antimicrobial peptides such as defensins and surfactant proteins. Alveolar macrophages patrol the airspaces, phagocytosing pathogens and producing cytokines that orchestrate inflammation. Epithelial and myeloid cells express pattern recognition receptors including Toll-like receptors and cytosolic sensors that detect conserved microbial motifs, triggering the release of chemokines to recruit neutrophils and monocytes. Neutrophils execute rapid antimicrobial responses through phagocytosis, degranulation and reactive oxygen species generation. Innate lymphoid cells and dendritic cells further modulate local immunity and shape the transition to adaptive responses. Tight regulation of these processes is essential to eliminate pathogens while preserving alveolar integrity and gas exchange. Advances in understanding signalling networks, cellular heterogeneity and epithelial–immune cross-talk are opening avenues for host-directed therapies in pneumonia and acute lung injury.

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Innate Immune Responses in Pulmonary Infections publication trend

The graph below shows the total number of articles in innate immune responses in pulmonary infections across all publications each year (not limited to Nature Index journals).

Technical terms

Alveolar macrophage: Resident phagocytic immune cell in the airspaces that engulfs pathogens and initiates inflammatory signalling.

Neutrophil: Short-lived leukocyte that migrates rapidly to sites of infection, releasing antimicrobial granules and reactive oxygen species.

Pattern recognition receptor: Germline-encoded receptor that detects conserved microbial components to trigger innate immune responses.

Toll-like receptor: Family of membrane-associated pattern recognition receptors that recognise pathogen motifs and activate downstream signalling.

Reactive oxygen species: Chemically reactive molecules produced by innate cells to kill pathogens but requiring tight regulation to prevent tissue damage.

References

1. Neutrophil subsets enhance the efficacy of host-directed therapy in pneumococcal pneumonia. Mucosal Immunology (2024).
2. The RNA receptor RIG-I binding synthetic oligodeoxynucleotide promotes pneumonia survival. JCI Insight (2024).
3. Innate immune responses in pneumonia. Pneumonia (2023).