The immune system maintains homeostasis by preventing pathogens from disrupting the body's normal functioning. It achieves this in various ways, including adaptive immunity when the body encounters a new pathogen, innate immunity, secreting acids onto the skin and using mucus membranes to breakdown bacteria.
Several factors can disrupt homeostasis, including viruses and other microorganisms that induce fevers, raise blood pressure and alter blood pH. The immune system maintains homeostasis by preventing such microorganisms from becoming problematic and reducing their ability to disrupt normal functioning. For example, in adaptive immunity, the immune system remembers a pathogen when it first enters the body. When it enters the body for the second time, it immediately tackles it, preventing it from causing a second infection and disrupting homeostasis.
There are several ways the immune system protects the body, including the skin, antigens and mucus membranes. The skin is the body's first line of defense. The immune system promotes a skin pH that deters some bacteria. When antigens encounter a foreign substance, they remember it and later produce antibodies when it enters the bloodstream again. The respiratory tract is home to mucus membranes and cilia. The mucus membranes have enzymes that tackle pathogens, and the cilia sweep them away.