Host-pathogen interaction in community-acquired pneumonia: a focus on the immune response

Community-acquired pneumonia (CAP) remains one of the leading causes of morbidity and mortality worldwide, affecting individuals of all ages. Various pathogens can cause this condition, and growing antibiotic resistance makes treatment more difficult while raising the risk of severe outcomes. Despite substantial advances in diagnostics, antimicrobial therapy, and supportive care, CAP continues to represent a significant clinical and public health challenge. In this review, we provide a comprehensive overview of CAP, summarizing key aspects of its epidemiology, pathogen frequency, and recent progress in diagnostic tools and biomarkers. We also describe the innate and adaptive immune responses involved in CAP, with a particular focus on pneumonia caused by Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, respiratory syncytial virus, severe acute respiratory syndrome coronavirus 2, and Influenza A and B viruses. A deeper understanding of CAP immunopathogenesis may support the development of improved diagnostic and therapeutic approaches for pneumonia management.