This lesson will talk about what defines an autoimmune disease, a hypersensitivity reaction, and more. We'll also discuss Graves' disease and myasthenia gravis.
When police officers or military personnel undergo training, they need to learn how to recognize the bad guy from the good guy. They need to quickly react. They need to accurately shoot the burglar but purposefully avoid shooting the person being burglarized. Sometimes, due to a bad judgment call or poor training, friendly fire does occur. The friendly fire ends up hurting the good guys. This same type of deal can occur in our body as well.
When our own body's white blood cells, called lymphocytes, undergo maturation and training, they learn to recognize what is considered to be a friend, like a cell that belongs to our body, and what is the bad guy, like a virus or bacteria. They do this by being exposed to antigens, the little particles of the cells I mentioned, which our immune system can recognize and respond to.
However, sometimes these training processes go haywire for more than one reason. These reasons and how they develop and progress are outside of the scope of this lesson. However, what you need to know is that sometimes an autoimmune disease, or an immune response specific to self-antigens, can occur.
Normally, the cops, our lymphocytes, train to purposefully ignore shooting the good guy, the self-antigen - meaning the police officers don't just not shoot the good guy because they were trained to only shoot the bad guy. No, they actively avoid shooting the good guy as much as they actively try and shoot the bad guy. Self-tolerance, the ability to not attack our own body's antigens, is an active physiological process.
Therefore, any time that our body overreacts to a self-antigen and begins to produce antibodies directed against our own body's cells or receptors, called autoantibodies, or allows self-reactive lymphocytes called T cells to damage our body's cells, we call this autoimmunity.
Autoimmunity is just one cause of something known as a hypersensitivity reaction. A hypersensitivity reaction is a reaction in which our own body's immune cells overreact to an antigen and cause excessive inflammation and damage to our own body's cells and receptors in the process.
I don't want you to think, however, that all hypersensitivity reactions are autoimmune diseases. That's not true!
Autoimmune diseases have cops, the lymphocytes, that directly target the good guys and avoid the bad guys altogether. A hypersensitivity reaction can be either that or a process whereby a cop targets a bad guy but also hits a good guy by accident with the same shot - meaning the cop damages our own body's cells indirectly, or by extension, and in the process of trying to get the bad guy, like a virus or bacteria.
Examples of Autoimmune Disease
In any case, some famous examples of autoimmune diseases include myasthenia gravis and Graves' disease. In the former, antibodies target our own body's receptors at the neuromuscular junction and block certain chemicals from binding to and stimulating the receptors on the muscle cells that cause muscles to contract. This causes things like difficulty walking, eating, talking, and so on - basically anything that involves the use of your muscles.
In Graves' disease, the exact opposite occurs. Instead of the antibodies blocking a receptor, as in myasthenia gravis, the autoantibodies bind to receptors in the thyroid gland and actually mimic a normal hormone in your body. Once these autoantibodies bind to receptors in the thyroid gland, they cause the overproduction of thyroid hormones, thereby leading to hyperthyroidism. This condition leads to everything from a rapid heartbeat to weight loss to even exophthalmos, or the bulging of the eyes, because this autoantibody also seems to affect the muscles around the eyes.
In this lesson, we covered the basics of what makes an autoimmune disease, or an immune response specific to self-antigens.
Autoimmunity involves autoantibodies, which are antibodies directed against our own body's cells or receptors.
Autoimmunity is just one cause of something known as a hypersensitivity reaction, which is a reaction in which our own body's immune cells overreact to an antigen and cause excessive inflammation and damage to our own body's cells and receptors in the process.
Two famous examples of an autoimmune disease include Graves' disease and myasthenia gravis.
Following this lesson, you'll be able to:
- Describe what an autoimmune disease is
- Define autoantibodies
- Differentiate autoimmunity from the broader category of hypersensitivity reaction
- Explain what happens when a person has Graves' disease and myasthenia gravis