Logan Reed
Antibodies are protective proteins produced by the immune system in response to foreign substances known as antigens. They play a crucial role in maintaining the body's defence mechanism by attaching to these antigens and facilitating their elimination from the body. Antibodies are present in various bodily fluids and locations, including the skin, lungs, saliva, breast milk, and blood. They exhibit immune tolerance by recognizing and attacking foreign antigens while refraining from targeting the body's own tissues or self-antigens. While antibodies perform a diverse range of functions, there may be aspects or specific antigens that they do not address. Understanding the limitations of antibodies is essential in the context of medical research and treatment options.
| Characteristics | Values |
|---|---|
| What antibodies do | Attach to antigens (foreign substances) such as bacteria, fungi, viruses and toxins, and remove them from the body |
| Produced by the immune system | |
| Lab-made monoclonal antibodies are used to treat certain health problems, such as cancer, heart disease, rheumatoid arthritis, etc. | |
| Located in various areas of the body, including skin, lungs, tears, saliva, and breast milk | |
| Are proteins | |
| Each antibody has four polypeptides, including two heavy chains and two light chains | |
| Antibodies do not attach to self-antigens (this is called "immune tolerance") | |
| Antibodies can be passed from mother to fetus via the placenta | |
| Antibodies can be passed from mother to baby via breast milk | |
| Antibodies can neutralize viruses by blocking their attachment to host receptors | |
| Antibodies can promote the killing of certain blood forms by certain cells | |
| Antibodies can abolish the infectivity of certain gametes to mosquitoes | |
| Antibodies can have beneficial or adverse consequences for the host | |
| Antibodies can be used to localize cellular components | |
| What antibodies do not do | N/A |
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What You'll Learn
Antibodies do not attack self-antigens, only foreign antigens
Antibodies are protective proteins produced by the immune system. They attach to antigens (foreign substances) such as bacteria, fungi, viruses, and toxins, and remove them from the body. Antibodies are located in various areas of the body, including the skin, lungs, tears, saliva, and even breast milk.
Antigens are molecules present on the surface of cells that bind to receptors on antibodies or on the surface of lymphocytes. Antigens are classified based on where they originate, and the immune system discriminates between native and foreign antigens to fight against pathogens. There are three types of antigens: autoantigens (self-antigens), endogenous antigens (produced in bacteria or viruses living within the body), and exogenous antigens (produced outside the body and are foreign to the immune system).
The immune system ensures that self-antigens do not trigger an immune response through a process known as "central tolerance" or "negative selection" during the development of B and T cells. Lymphocytes with antigen-binding sites that might bind to and become activated by self-antigens are eliminated during cellular development. This process of immune tolerance ensures that only lymphocytes that are unreactive with self-antigens (i.e., B or T cells that only react with non-self-antigens) reach maturity and participate in the immune system.
In some cases, however, antibodies can mistakenly attack self-antigens, leading to autoimmune diseases. Autoimmune diseases occur when the body's adaptive immune response targets self-antigens instead of foreign antigens. This can result in chronic inflammatory injury to tissues, which may prove lethal. An example of an autoimmune disease is autoimmune hemolytic anemia, where antibodies against self-antigens on red blood cells trigger the destruction of those cells, leading to anemia.
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Antibodies do not provide long-lasting protection when injected as antiserum
Antibodies are protective proteins produced by the immune system. They attach to antigens (foreign substances) such as bacteria, fungi, viruses, and toxins, and remove them from the body. Antibodies are located in various areas of the body, including the skin, lungs, tears, saliva, and even breast milk.
Passive immunization is a process by which antibodies are injected into the body. These antibodies are formed in another person or animal's body. Passive immunization provides immediate protection against an antigen but does not provide long-lasting protection. Antiserum, a blood serum containing specific antibodies against an antigen, is often used in passive immunization. Antibodies in antiserum work by detecting and neutralizing antigens. While antiserum can be produced in animals, it can also be produced in humans in response to infection, vaccination, or intoxication.
The use of antiserum from animals can lead to serious allergic reactions in the recipient. Additionally, antibody treatments often require intravenous injection, which is more time-consuming and potentially complicated than other injection methods. The immunity conferred by passive immunization is short-lived because it does not lead to the formation of long-lasting memory immune cells. In contrast, active immunity, where a person's immune system produces antibodies, results in long-lasting protection.
The limitations of passive immunization highlight the importance of developing long-lasting immunity through active methods such as vaccination. Vaccines work by causing acquired immunity without the need for prior infection. This allows the immune system to build a defense against specific antigens, providing long-term protection.
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Antibodies do not attach to self-tissues
Antibodies are protective proteins produced by the immune system. They attach to antigens (foreign substances) such as bacteria, fungi, viruses, and toxins, and remove them from the body.
The body's own cells have markers called human leukocyte antigens (HLAs) that identify them as "self". All of our cells have HLAs except red blood cells. The body does not produce antibodies to attack these self-antigens. This is called "immune tolerance".
In some cases, an overactive immune response can lead to the development of autoimmune diseases, in which antibodies form against the body's own tissues. This can happen if an individual has antibodies to HLAs, causing an autoimmune disease if they happen to be their own. For example, in organ transplants, recipients are tested to ensure they do not have antibodies to the donor's HLAs, which would cause their body to attack the donated organ.
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Antibodies do not alter their cognate antigen
Antibodies are protective proteins produced by the immune system. They attach to antigens, which are foreign substances such as bacteria, fungi, viruses, and toxins, and remove them from the body. Antibodies are located in various areas of the body, including the skin, lungs, tears, saliva, and even breast milk.
The importance of antibodies in healthcare and biotechnology has led to the development of various techniques to study their structures, such as X-ray crystallography and computational approaches. Antibodies have two identical antigen-binding sites, which allow them to cross-link antigens. The binding site can alter its shape after antigen binding to better fit the ligand. However, the rest of the antibody's structure is much less variable.
Vaccines work by imitating antigens, triggering the production of specific antibodies. These antibodies then lie dormant in the body until they are needed to fight the infection caused by the antigen. This is why vaccinated individuals can often avoid getting sick when exposed to the actual infection.
In summary, antibodies play a crucial role in protecting the body from antigens, and their specificity ensures that they do not alter their cognate antigen.
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Antibodies do not bind directly to the virus attachment site
Antibodies are protective proteins produced by the immune system. They are synthesised exclusively by B cells, which are produced in the bone marrow and mature in the periphery. B cells produce antibodies in response to antigens (foreign substances) such as bacteria, fungi, viruses and toxins.
Each antibody has a unique structure, composed of two heavy chains and two light chains, which combine to form a Y-shaped molecule. The antigen-binding sites are located at the tips of the "Y", and it is here that antibodies attach to antigens.
However, antibodies do not bind directly to the virus attachment site. Instead, they bind to antigens in order to neutralise them. Antibodies also activate the complement system to destroy bacterial cells and facilitate phagocytosis of foreign substances by phagocytic cells.
The diversity of antibodies is such that they can recognise all types of antigens, except self-antigens. This is called "immune tolerance". This feature ensures that self-cells and tissues are not attacked by antibodies.
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Frequently asked questions
Antibodies are protective proteins produced by the immune system. They attach to antigens (foreign substances) and remove them from the body.
Antibodies do not attack self-antigens. This is called "immune tolerance".
Examples of antigens include bacteria, fungi, viruses, and toxins.
Antibodies are located in various areas of the body, including the skin, lungs, tears, saliva, and breast milk.
Antibodies attach to specific antigens, making it easier for immune cells to destroy them. They can also neutralize pathogens by blocking their attachment to host receptors.
