What are Antibodies

If this is the first time you have heard about antibodies, you may not know how important they are. Antibodies are one of the warriors inside our body, helping us to fight off nasty, invading particles. They are a type of protein, and are a key component of our immune system. If a person doesn’t produce, or over-produces, antibodies in their body, the person will become very ill. So where do antibodies come from? Antibodies circulate in the bloodstream and can appear anywhere throughout the body. Their function is to recognize bad agents, called antigens, and then trigger further chemical reactions in the body to remove the antigens. Antigens are foreign substances that are capable of triggering an immune response. They can be viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, and foreign particles. They can even be allergens like dust, pollen or certain foods, that cause allergic reactions. Antibodies are produced by the immune system in response to the presence of an antigen. So what do antibodies look like? Antibodies are also known as immunoglobulin. They are generally a Y-shaped protein consisting of four polypeptides: 2 identical light chains, and 2 identical heavy chains. the terms light and heavy simply mean larger and smaller. The 4 polypeptide chains are connected by disulphide bridges. Here, at the tip of each arm are the antigen binding sites. These are the really important parts for attacking invading antigens. Similar to the lock and key mechanism in enzymes, the shape of the antigen binding site is specific to the antigen it is targeting. If part of the antigen fits into the antigen binding site, the antibody “recognizes” the foreign antigen and binds it in. This stops the antigen from causing more damage elsewhere. Two identical binding sites means any given antibody can bind simultaneously to two identical antigens. Millions of antibodies with slightly different tip structures exist, with each variant binding to a different antigen. This enormous diversity of antibodies allows the immune system to recognize an equally diverse range of antigens. By binding in an antigen, an antibody can stop the antigen from entering or damaging cells. This is known as neutralizing. The antibody can also tag the antigen for attack by other parts of the immune system. In mammals there are five immunoglobulin isotypes. They perform different roles, and help direct the appropriate immune response for each different type of foreign invader. Antibodies are cloned in laboratories. So there we have the ninja Y-shaped antibodies - protecting us from foreign invading antigens. Antibodies are nearly identical, except for slightly different shaped antigen binding sites.