Antigen

Antigens are substances that stimulate the immune system to produce antibodies against them. They are usually protein or polysaccharide molecules that are present on the surface of cells or viruses. When an antigen enters the body, it is recognized by the immune system as a foreign substance and triggers the production of specific antibodies that bind to and neutralize the antigen.

Types of Antigens

There are two types of antigens: self-antigens and foreign antigens. Self-antigens are molecules that are present on the surface of the body's own cells and do not usually stimulate an immune response. Foreign antigens, on the other hand, are substances that are not normally present in the body and are recognized as foreign by the immune system.

Functions of Antigens

The primary function of antigens is to stimulate the production of antibodies by the immune system. Antibodies are proteins that are produced by specialized cells of the immune system called B cells. When antibodies bind to antigens, they can neutralize or eliminate them from the body.

Examples of Antigens

Examples of antigens include:

- Bacteria and viruses
- Pollen and dust mites
- Foods, such as peanuts or shellfish
- Drugs, such as penicillin
- Transplanted organs, such as a kidney

Conclusion

Antigens are substances that stimulate the immune system to produce antibodies against them. They are usually protein or polysaccharide molecules that are present on the surface of cells or viruses. When an antigen enters the body, it triggers the production of specific antibodies that bind to and neutralize the antigen.