The Complement System: A Bridge Between Innate and Adaptive Immunity and an Influencer of Eosinophilic Inflammation in Respiratory Diseases

The complement system is a key link between innate and adaptive im-munity, participating in the elimination of pathogens, the regulation of immune responses and the maintenance of tissue homeostasis. Its activa-tion is not only crucial in infections, such as COVID-19, but also plays a prominent role in the pathomechanism of several non-infectious respira-tory diseases, such as asthma, COPD, sarcoidosis and lung cancer. Com-plement components can influence the quality of the adaptive response, including through the regulation of T2 immunity and eosinophilic in-flammation, thereby linking natural defense to complex immune process-es. In recent years, it has become increasingly clear that dysregulation of the complement system contributes to the development of inflammation, thrombosis and tissue damage in a wide range of respiratory diseases. The study of the various components of this cascade system may therefore be promising from both a diagnostic and therapeutic point of view. Some of its components may serve as biomarkers for distinguishing between dif-ferent phenotypes of certain lung diseases, while their targeted inhibition or modulation may open the way towards new treatment options. A better understanding of the complement system's connecting role not only allows for a deeper exploration of immunological relationships, but may also bring us closer to personalised, immunology-based pulmonology, which may have real clinical benefits in the future.