Immune System and Disorders
Source: MedlinePlus Health Topics, U.S. National Library of Medicine
What is the immune system? Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases. When germs such as bacteria or viruses invade your body, they attack and multiply. This is called an infection. The infection causes the disease that makes you sick. Your immune system protects you from the disease by fighting off the germs. What are the parts of the immune system? The immune system has many different parts, including: Your skin, which can help prevent germs from getting into the body Mucous membranes, which are the moist, inner linings of some organs and body cavities. They make mucus and other substances which can trap and fight germs. White blood cells, which fight germs Organs and tissues of the lymph system , such as the thymus, spleen , tonsils, lymph nodes, lymph vessels, and bone marrow . They produce, store, and carry white blood cells. How does the immune system work? Your immune system defends your body against substances it sees as harmful or foreign. These substances are called antigens. They may be germs such as bacteria and viruses. They might be chemicals or toxins. They could also be cells that are damaged from things like cancer or sunburn . When your immune system recognizes an antigen, it attacks it. This is called an immune response. Part of this response is to make antibodies. Antibodies are proteins that work to attack, weaken, and destroy antigens. Your body also makes other cells to fight the antigen. Afterwards, your immune system remembers the antigen. If it sees the antigen again, it can recognize it. It will quickly send out the right antibodies, so in most cases, you don't get sick. This protection against a certain disease is called immunity. What are the types of immunity? There are three different types of immunity: Innate immunity is the protection that you are born with. It is your body's first line of defense. It includes barriers such as the skin and mu