Antigens VS Antibodies Explained

Показать описание

In the last video, I told you that pathogens are a fancier word for germs and that they have these “IDs” called antigens which allow the body to recognize them. Well, an antigen is in fact any substance that causes your immune system to produce antibodies against it. In other words an antigen is a molecule which triggers an immune response. Therefore, an antigen is not recognized by your immune system or in other words, your immune system recognizes it as foreign and tries to fight it off. Each antigen has distinct surface features called epitopes.

The epitope is the smallest part of an antigen which is recognized by our immune system as “foreign” and binds an antibody. The specific part of the antibody which binds to the epitope is called the paratope.

In response to antigens, the body produces antibodies or immunoglobins which are Y-shaped proteins produced by B cells of the immune system. Each antibody contains a paratope which recognizes a specific epitope on an antigen, acting like a lock and key binding mechanism. This is because antibodies are usually “specific” to antigens, therefore each type of antibody has a sort of “soulmate” to which it binds. This binding helps to eliminate antigens from the body, either by direct neutralization or by “tagging” for other parts of the immune system. This is the same reason that if a pathogen mutates, thereby changing it antigen, a new type of antibody has to be produced in response to it.

When infected with a pathogen such as SARS-CoV-2, the body produces antibodies that bind specifically to the antigens to help eliminate the pathogen. This binding can be harnessed to develop antibody and antigen-based diagnostic tests. Such tests, commonly called immunoassays can detect the presence of a pathogen due to its antigen which a specific monoclonal antibody may bind to.

Vaccines are examples of antigens in an immunogenic form, which are intentionally administered to a patient to induce the memory function of the adaptive immune system towards antigens of the pathogen invading that patient. In, this way antigens can be used to “train” the body to quickly respond to future “attacks” of the same pathogen.