Surfactant Protein A (SP-A) is a protein that plays a crucial role in the lungs. It is part of the surfactant system, which helps reduce surface tension in the alveoli, the tiny air sacs where gas exchange occurs. By doing so, SP-A helps keep the lungs inflated and prevents them from collapsing. In addition to its role in lung function, SP-A is involved in the immune response. It helps recognize and bind to pathogens, such as bacteria and viruses, enhancing the body's ability to fight infections. This makes SP-A important for overall respiratory health and defense against respiratory diseases.