What is the basic function of the immune system?

The immune system's primary role is to protect the body from pathogens, such as bacteria, viruses, fungi, and parasites, as well as to prevent diseases that can arise from these infectious agents. This system consists of a complex network of cells, tissues, and organs that work together to identify and eliminate harmful invaders. When the body detects a foreign substance, immune cells are activated to respond swiftly and effectively, utilizing various strategies such as producing antibodies to neutralize pathogens, mobilizing white blood cells to attack infected cells, and creating memory cells for faster responses in the future. This protective function is essential for maintaining overall health and ensuring the body's ability to ward off infections and diseases.

While other choices may address different bodily functions—such as regulating body temperature, facilitating gas exchange in the lungs, or storing energy in fat and muscle tissues—they do not pertain to the immune system's fundamental role. The immune system is specifically dedicated to defense against disease, which underscores why the correct answer centers on its protective capabilities.