Immune Responses to Respiratory Infections

The respiratory system is a complex system representing both a physical and immunological barrier between the external environment and the blood and tissues. It provides gas exchange and oxygenation of the blood and is a crucial component of the body’s defenses against various pathogens that can cause infections. In response to harmful microorganisms entering the respiratory tract, such as viruses, bacteria, fungi, and protozoa, a complex and multifaceted response occurs. Respiratory cells and innate immune cells initiate the clearing and resolution of infection, followed by the intervention of adaptive immune cells. A range of cellular and molecular mechanisms are involved in this immune response, which is responsible for identifying, neutralizing, and eliminating the invading pathogens. Recurrent and severe respiratory tract infections, particularly if caused by atypical pathogens, are indeed listed among the key warning signs that should raise the suspicion of an Inborn Error of Immunity (IEI), both in pediatric and adult patients. Acute respiratory tract infections (ARTIs) are the leading cause of symptomatic illness worldwide and are frequently caused by viruses, although bacteria and fungi can also cause ARTIs. Both innate and adaptive defense systems are involved in antimicrobial immunity.