Antigens stimulate the immune system to produce antibodies to defend against foreign substances, but can also cause harmful allergic reactions. Medical tests can identify unique antibodies to determine exposure to disease or toxins. Antigens can come from bacteria, viruses, toxins, and transplanted organs. Allergies occur when the body develops an antigenic response to something harmless.
An antigen is a substance that stimulates an immune response. When exposed to an antigen, the body sees it as foreign material and takes steps to neutralize it. Typically, the body accomplishes this by producing antibodies, which are intended to defend the body against the invasion of potentially dangerous substances. Several medical tests can be used to test substances, to determine whether or not someone has been exposed to a disease or toxin.
The term “antigen” comes from the understanding that many foreign substances stimulate the generation of antibodies within the immune system. These antibodies can be helpful, as in the case when the body learns to fight a virus such as measles, or they can be harmful, in the case of allergies. The unique signatures of these antibodies can be identified in medical tests, which can be used to determine why a patient is exhibiting a variety of symptoms.
Most animals have what is known as an adaptive immune system. Within the immune system, a number of cells perform specific functions that help the immune system recognize and deal with potential threats to its host. Some of these cells learn to recognize substances that do not come from the host organism. When an antigen is identified, these cells warn other cells of the problem and the body takes action.
Many things can be sources of antigens. Humans can inhale or ingest bacteria and viruses from other organisms, for example. A toxin can also be a source, as the body realizes that the substance is foreign and potentially dangerous. Transplanted organs and tissue material can also generate an antibody response because the body does not recognize them as part of the host organism. Because of this problem, people who undergo organ transplants take immunosuppressant drugs designed to limit the response so the body does not reject the introduced organ.
Sometimes, the body develops an antigenic response to something that isn’t actually harmful. This is better known as an allergy. In these cases, the body is exposed to a small amount of the antigen, such as peanut butter, grain or bee sting. The helper cells of the immune system label the substance, causing the body to produce cells that will counteract the substance if it reappears in the body. When the unwitting human host eats peanuts, munches on a slice of toast, or is stung by a bee again, the body mounts an antibody response that can cause severe discomfort and sometimes even death.
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