Immunity is the way your body defends itself against bacteria, viruses, fungi, and other substances that appear to be foreign and harmful. Your immune system attacks and destroys these substances, which are called antigens. Antigens can be proteins on the surface of living cells, or they can be nonliving particles such as a splinter or a piece of hay.
Your immune system is a network of organs, white blood cells and proteins that work together to protect your body from germs and other invaders. It also helps your body fight off infections and heal from injuries.
The first part of your immune system is innate immunity, which is active from the time you are born. It creates physical barriers, such as the skin and mucous membranes that line the respiratory, digestive, and genitourinary tracts. It also responds quickly to an infection by sending out a variety of cells to surround and capture the pathogen.
In the next phase, the adaptive immune response begins. This involves two types of lymphocytes, which are key players in the immune response. B lymphocytes are like the body’s military intelligence system, finding invaders and directing T cells to lock onto them. T cells are like soldiers, attacking and destroying the invaders that B cells find.
The adaptive immune response can build up memory against certain antigens, which allows the immune system to react faster and more efficiently when the same invaders come back. This is the principle behind vaccines, which can prevent you from getting diseases such as polio and chickenpox by immunizing you against these diseases.
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