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Antigens and antibodies are two entirely different things. For the uninitiated, an antibody is a glycoprotein that is produced in response to and counteracts the effects of a specific antigen. An antigen, on the other hand, is a foreign substance (usually harmful) that triggers an immune response, resulting in the production of antibodies in the body.Antigens are molecules that have the ability to activate an immune response. Each antigen has a unique set of surface characteristics, known as epitopes, that cause it to elicit a specific immune response. When the immune system encounters an antigen, antibodies (immunoglobulins) are produced by B cells. Antibodies are Y-shaped proteins that are produced by B cells in response to the antigen.
Antigens
Immune responses to pathogens, such as bacteria, fungi, viruses, and other foreign particles, are triggered by large protein molecules on the surface of the pathogen. When these harmful agents enter the body, they trigger an immune response that allows antibodies to be formed.
As an illustration, consider the following: When a standard cold virus enters the body, it causes the body to produce antibodies in order to prevent the person from becoming ill.
Characteristics of Antigens
The following are the characteristics of antigens:
- To elicit an immune response, the antigen should be a foreign substance that is not readily recognised.
- They have a molecular mass between 14,000 and 6,00,000 Da and are classified as antigenic.
- Proteins and polysaccharides constitute the majority of them.
- A substance’s immunogenicity is proportional to how chemically complex it is.
- It is necessary to distinguish between species when dealing with antigens.
- Immunogenicity is affected by one’s age. Extremely young children and the elderly are immunogenic to a very small degree.
Antibodies
An antibody is also referred to as an immunoglobulin in some circles. Plasma cells produce these large, Y-shaped blood proteins, which are large in size and shape. They attach themselves to foreign particles and infiltrate them. When foreign pathogens enter the body, they have the potential to elicit an immune response from our immune system, either by grouping together with a larger molecule or by acting alone after binding with antibodies to trigger a specific immune response. As a result, antigens stimulate the production of antibodies by the immune system.
Structure of Antibody
An antibody molecule is composed of four polypeptide subunits that are arranged in a Y shape. One of the heavy chains forms an association with one of the light chains, resulting in the formation of two antigen-binding domains. Fragment antigen binding (Fab) domains are the arms of the “Y” shape and are responsible for binding antigen fragments. During the antibody’s interaction with the effector cells, it plays an important role. The disulfide and non-covalent bonds that hold all four polypeptide subunits together are responsible for their stability. The variable region of the antibodies is sandwiched between three constant regions in the large chains. Each antibody contains two antigen-binding sites that are identical to one another, but they differ between antibodies.
Difference between Antigen And Antibody
| Basis | Antigen | Antibody |
| Known as | Immunogens | Immunoglobulins |
| Molecular Type | Antigens are typically lipids in nature. Proteins, carbohydrates, and nucleic acids are all examples of macromolecules. | All antibodies are made up of proteins. |
| Effect | Allergic reactions and even illnesses can be caused by antigens. | Protection against the impacts of the antigen is achieved through either lysis or immobilisation of the antigen particle. |
| Origins | Antigens come from places other than the body. | Antibodies are always produced by the body. |
| Specific Binding Site | These are regions of the antigen where antibodies can bind and interact with it. | It is the variable regions of an antibody that bind to an epitope that are known as paratopes. |
Conclusion
In order for acquired immunity to work, antigens and a group of proteins known as antibodies, which are produced by B cells in the bloodstream, must come into contact with one another. The antigens that antibodies recognise are numerous, and each antibody recognises a different type of antigen. As a result, the precise binding of antigens to antibodies causes the immune response in acquired immunity.One of the most fundamental applications is the identification of ABO blood groups. As a molecular method, it is also used to diagnose infection with various pathogens, including HIV, microbes, and helminth parasites.
