“The immune system is the body’s defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
About the Immune System
The immune system is the body’s defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. One of the important cells involved are white blood cells, also called leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.
Leukocytes are produced or stored in many locations in the body, including the thymus, spleen, and bone marrow. For this reason, they’re called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes.
The leukocytes circulate through the body between the organs and nodes via lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.
The two basic types of leukocytes are:
Here’s how it works:When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, which are specialized proteins that lock onto specific antigens.
Once produced, these antibodies stay in a person’s body, so that if his or her immune system encounters that antigen again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person usually won’t get sick from it again.
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen in a way that doesn’t make someone sick, but does allow the body to produce antibodies that will then protect the person from future attack by the germ or substance that produces that particular disease.
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That’s the job of the T cells, which are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (Some T cells are actually called “killer cells.”) T cells also are involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies also can neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.
Problems of the Immune System
Disorders of the immune system fall into four main categories:
Acquired (secondary) immunodeficiencies include:
Allergic disorders happen when the immune system overreacts to exposure to antigens in the environment. The substances that provoke such attacks are called allergens. The immune response can cause symptoms such as swelling, watery eyes, and sneezing, and even a life-threatening reaction called anaphylaxis. Medicines called antihistamines can relieve most symptoms.
Allergic disorders include:
About the Immune System
The immune system is the body’s defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. One of the important cells involved are white blood cells, also called leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.
Leukocytes are produced or stored in many locations in the body, including the thymus, spleen, and bone marrow. For this reason, they’re called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes.
The leukocytes circulate through the body between the organs and nodes via lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.
The two basic types of leukocytes are:
- phagocytes, cells that chew up invading organisms
- lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them
Here’s how it works:When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, which are specialized proteins that lock onto specific antigens.
Once produced, these antibodies stay in a person’s body, so that if his or her immune system encounters that antigen again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person usually won’t get sick from it again.
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen in a way that doesn’t make someone sick, but does allow the body to produce antibodies that will then protect the person from future attack by the germ or substance that produces that particular disease.
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That’s the job of the T cells, which are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (Some T cells are actually called “killer cells.”) T cells also are involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies also can neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.
Problems of the Immune System
Disorders of the immune system fall into four main categories:
- immunodeficiency disorders (primary or acquired)
- autoimmune disorders (in which the body’s own immune system attacks its own tissue as foreign matter)
- allergic disorders (in which the immune system overreacts in response to an antigen)
- cancers of the immune system
Acquired (secondary) immunodeficiencies include:
- HIV (human immunodeficiency virus) infection/AIDS (acquired immunodeficiency syndrome) is a disease that slowly and steadily destroys the immune system. It is caused by HIV, a virus that wipes out certain types of lymphocytes called T-helper cells. Without T-helper cells, the immune system is unable to defend the body against normally harmless organisms, which can cause life-threatening infections in people who have AIDS. Newborns can get HIV infection from their mothers while in the uterus, during the birth process, or during breastfeeding. People can get HIV infection by having unprotected sexual intercourse with an infected person or from sharing contaminated needles for drugs, steroids, or tattoos.
Allergic disorders happen when the immune system overreacts to exposure to antigens in the environment. The substances that provoke such attacks are called allergens. The immune response can cause symptoms such as swelling, watery eyes, and sneezing, and even a life-threatening reaction called anaphylaxis. Medicines called antihistamines can relieve most symptoms.
Allergic disorders include:
- Asthma, a respiratory disorder that can cause breathing problems, often involves an allergic response by the lungs. If the lungs are oversensitive to certain allergens (like pollen, molds, animal dander, or dust mites), breathing tubes can become narrowed and swollen, making it hard for a person to breathe.
- Eczema is an itchy rash also known as atopic dermatitis. Although not necessarily caused by an allergic reaction, eczema most often happens in kids and teens who have allergies, hay fever, or asthma or who have a family history of these conditions.
- Allergies of several types can affect kids and teens. Environmental allergies (to dust mites, for example), seasonal allergies (such as hay fever), drug allergies (reactions to specific medications or drugs), food allergies (such as to nuts), and allergies to toxins (bee stings, for example) are the common conditions people usually refer to as allergies.