White blood cells, also called leukocytes LOO-kuh-sytes , play an important role in the immune system. Some types of white blood cells, called phagocytes FAH-guh-sytes , chew up invading organisms. Others, called lymphocytes LIM-fuh-sytes , help the body remember the invaders and destroy them. One type of phagocyte is the neutrophil NOO-truh-fil , which fights bacteria.
When someone might have bacterial infection, doctors can order a blood test to see if it caused the body to have lots of neutrophils. Other types of phagocytes do their own jobs to make sure that the body responds to invaders. The two kinds of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes start out in the bone marrow and either stay there and mature into B cells, or go to the thymus gland to mature into T cells.
B lymphocytes are like the body's military intelligence system — they find their targets and send defenses to lock onto them. T cells are like the soldiers — they destroy the invaders that the intelligence system finds. When the body senses foreign substances called antigens , the immune system works to recognize the antigens and get rid of them. B lymphocytes are triggered to make antibodies also called immunoglobulins. These proteins lock onto specific antigens.
After they're made, antibodies usually stay in our bodies in case we have to fight the same germ again. When this system recognizes an invader, it goes into action immediately. The cells of this immune system surround and engulf the invader. The invader is killed inside the immune system cells.
These cells are called phagocytes. The acquired immune system, with help from the innate system, produces cells antibodies to protect your body from a specific invader. These antibodies are developed by cells called B lymphocytes after the body has been exposed to the invader. The antibodies stay in your child's body. It can take several days for antibodies to develop. But after the first exposure, the immune system will recognize the invader and defend against it.
The acquired immune system changes throughout your child's life. Immunizations train your child's immune system to make antibodies to protect him or her from harmful diseases. Lymph nodes. Small organs shaped like beans, which are located throughout the body and connect via the lymphatic vessels.
Lymphatic vessels. This innate immunity includes the external barriers of our body — the first line of defense against pathogens — such as the skin and mucous membranes of the throat and gut. This response is more general and non-specific. If the pathogen manages to dodge the innate immune system, adaptive or acquired immunity kicks in. This protect from pathogens develops as we go through life. As we are exposed to diseases or get vaccinated, we build up a library of antibodies to different pathogens.
This is sometimes referred to as immunological memory because our immune system remembers previous enemies. For instance, a baby receives antibodies from the mother through the placenta before birth and in breast milk following birth. This passive immunity protects the baby from some infections during the early years of their life.
Immunization introduces antigens or weakened pathogens to a person in such a way that the individual does not become sick but still produces antibodies. Because the body saves copies of the antibodies, it is protected if the threat should reappear later in life.
Because the immune system is so complex, there are many potential ways in which it can go wrong. Types of immune disorder fall into three categories:. These arise when one or more parts of the immune system do not function. Immunodeficiencies can be caused in a number of ways, including age, obesity , and alcoholism. In developing countries, malnutrition is a common cause. AIDS is an example of an acquired immunodeficiency. In some cases, immunodeficiencies can be inherited, for instance, in chronic granulomatous disease where phagocytes do not function properly.
In autoimmune conditions, the immune system mistakenly targets healthy cells, rather than foreign pathogens or faulty cells. In this scenario, they cannot distinguish self from non-self. With hypersensitivity, the immune system overreacts in a way that damages healthy tissue. An example is anaphylactic shock where the body responds to an allergen so strongly that it can be life-threatening. The immune system is incredibly complicated and utterly vital for our survival.
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