Non-Self Antigens, Self-Antigens & Allergens

Non-Self Antigens, Self-Antigens & Allergens
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  • 0:04 Who Are You?
  • 1:44 Non-Self Antigens
  • 3:20 Allergies & Autoimmune…
  • 4:16 Antibodies & Transplantation
  • 5:01 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Your immune system uses antigens to identify which cells belong to you and which should be destroyed. In this lesson, learn about nonself-antigens, self-antigens, and allergens, and how your immune system responds to them.

Who Are You?

What makes you the unique person you are? Is it your great personality, the color of your eyes, or maybe the sound of your voice? While all of these are important, at a cellular level, it's actually your antigens.

Every cell in your body has markers that identify it as being uniquely YOU. Microorganisms like bacteria and viruses have their own unique markers as well, and your immune system looks for the presence of these markers to know when to attack. These markers, called antigens, are most often small proteins, but can also sometimes be fragments of nucleic acids, carbohydrates, or even fats.

The antigens on your own cells are known as self-antigens, while those that do not originate in your body are called non-self antigens. Self-antigens are present on all your cells, but they're particularly important in blood cells. You can only receive a blood transfusion from a donor with the same type of antigen. Otherwise your immune system will attack the donated blood because it will display antigens that are not recognized as being self-antigens.

Non-self antigens are present on bacteria and viruses such as influenza and tetanus, which invade your body and make you sick. They are also present in blood or organs transplanted from another person who has antigens different from yours.

If any non-self antigens are found inside your body, your immune system immediately goes to work trying to eradicate them. This is great when you're sick and need to kill viruses and bacteria, but the system is very sensitive, and there are many ways in which it can go wrong.

Non-Self Antigens

One type of white blood cell, the lymphocyte, is responsible for recognizing and reacting to non-self antigens. As lymphocytes grow and mature in your bone marrow and then thymus, they're exposed to your own antigens so they learn not to react to them. Once lymphocytes mature and are released into your body, they are always on the lookout for antigens they don't recognize as being a part of you. There are two types of lymphocytes, T-cells and B-cells; these work together to initiate an antibody response.

If a B-cell encounters a non-self antigen, it binds to it. With the help of a T-cell, the B-cell will become fully activated, and it will then start dividing to produce large plasma cells that release antibodies targeting the alien antigen. Each antibody has an antigen-binding site that will only attach to one specific type of antigen. When antibodies bind to antigens, it helps other parts of the immune system to locate and destroy invading microorganisms.

In addition to antibody-producing plasma cells, memory B-cells are also produced during an immune response. These can stay in your body for many years, and the presence of these memory B-cells means that if you're exposed to the same antigen again, antibody production starts much more quickly. This is the basis of vaccines. A vaccine contains pieces of a virus or bacteria that will trigger the production of antibodies and memory B-cells. Then your immune system will recognize the infectious agent, ready to immediately destroy it if you ever encounter it again.

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