How do antibodies differ from antigens?

Antibodies are proteins produced by the immune system to neutralise pathogens, while antigens are molecules that trigger this immune response.

Antibodies and antigens are both crucial components of the immune system, but they play very different roles. Antibodies, also known as immunoglobulins, are Y-shaped proteins produced by B cells, a type of white blood cell. Their primary function is to identify and neutralise foreign objects such as bacteria, viruses, and other pathogens. They do this by binding to specific sites on the pathogen, known as antigens, which effectively 'tags' the pathogen for destruction by other immune cells.

Antigens, on the other hand, are molecules capable of inducing an immune response. They are typically found on the surface of pathogens, but can also be produced by the body itself in certain situations, such as during an allergic reaction or in the presence of cancer cells. When an antigen enters the body, it is recognised as foreign by the immune system, which triggers the production of specific antibodies to neutralise it.

The interaction between antibodies and antigens is highly specific. Each antibody can only bind to a specific antigen, much like a lock and key. This specificity is determined by the structure of the antigen-binding site on the antibody, which is unique for each type of antibody. This means that for each new antigen that enters the body, a new type of antibody must be produced.

In summary, while both antibodies and antigens are integral to the immune response, they serve different functions. Antibodies are the body's 'defence' against foreign invaders, produced in response to the presence of antigens. Antigens, meanwhile, are the 'triggers' that stimulate this defensive response. Understanding the interaction between these two components is key to understanding how the immune system works to protect the body against disease.