From lungs to brain: the neuroimmune impact of respiratory microbiota

The bidirectional communication between the lungs and the central nervous system, known as the lung-brain axis, has emerged as an important framework for understanding systemic mechanisms influencing neurological health. Increasing evidence indicates that pulmonary inflammation, respiratory microbiota alterations, and environmental exposures can modulate neuroinflammation, blood-brain barrier integrity, and microglial activation.

This review summarizes current experimental and clinical evidence describing the molecular, microbial, and neuroimmune mechanisms underlying the lung-brain axis. Particular emphasis is placed on the role of the respiratory microbiota across the upper and lower airways and its interaction with immune signaling pathways. In addition, the neurological consequences of pulmonary diseases and infections, including asthma and COVID-19, are discussed, highlighting neuroanatomical, humoral, and immunological routes linking pulmonary and brain physiology.

Emerging data suggest that the respiratory system functions as an immunometabolic interface capable of influencing neuroimmune regulation and brain function. Integrative approaches combining respiratory microbiota profiling, immune biomarkers, and neuroimaging may help clarify causal mechanisms and support the development of novel diagnostic and therapeutic strategies for neurological and post-infectious conditions.