Lesson 3: Autoimmune Thyroid Disease
The Immune System
The immune system is a complex network of blood cells and organs that work together to protect us from disease. Our immune system cells consist of white blood cells. White blood cells known as lymphocytes are the key players and they're assisted by a smaller number of white cells known as monocytes and macrophage cells. These immune system cells constantly circulate through our bloodstream, watching for and guarding us against foreign antigens.
Our immune system organs, which include the bone marrow, spleen, thymus gland, tonsils, adenoids and lymph nodes, are the sites of white blood cell production. The bone marrow is the most important immune system organ. Here, the overwhelming majority of the body’s white blood cells are produced.
Our lymphocytes have a number of different surface markers that normally tell these cells what substances to react with. They also direct the severity of the reaction. These markers are under genetic control. Studies show that people with certain markers are more likely to develop certain autoimmune disorders.
Antigens and Antibodies Antigens are substances, usually protein in nature that the immune system is capable of reacting with. Antigens include protein particles that make up our body’s organs and cells, and proteins found in bacteria, viruses, pollen, toxins and other substances. Substances that are not normally found in the body, such as pollen, are called foreign antigens.
Our immune system’s cells work together to launch an immune response when they encounter foreign antigens. In this response, the cells produce specific proteins known as antibodies. The presence of specific antibodies can be used as disease markers. For instance, when the laboratory finds antibodies to a specific virus, it knows that the body has been exposed to this virus or it has been vaccinated against this virus. When we’re vaccinated, we receive a specific substance similar to the infectious agent. Our body then reacts by producing antibodies. Antibodies, in most cases, protect us from a second exposure to the infectious agent.
For instance, when we’re vaccinated or immunized against the poliovirus, our immune system produces polio antibodies. These antibodies react with and destroy polio particles. If we’re exposed to polio, these antibodies destroy the virus before it produces a disease.
Autoantibodies When our immune system is not working the way it should, it is inefficient. A weakened immune system loses the ability to distinguish between the body’s own antigens and foreign antigens. It begins to produces antibodies against the body’s own organs and cell components. These antibodies are known as autoantibodies. When the laboratory finds autoantibodies in the person’s blood, these autoantibodies can be used to diagnose certain diseases. Autoantibodies do not protect us from disease the way regular antibodies do. Autoantibodies cause autoimmune disorders. Normally, the human body does not have any autoantibodies.
Specific thyroid autoantibodies are known to perform specific actions. Most people with an autoimmune thyroid disease produce several different thyroid antibodies. The antibody that predominates determines what specific thyroid disorder a person has. Later in this lesson, we’ll learn about specific thyroid antibodies and their relationship to autoimmune thyroid diseases.
