What are antigens?

Antigens are foreign substances that enter the body and trigger an immune response. They are usually present on the surface of pathogens such as bacteria, viruses, fungi, or other harmful particles.

When antigens enter the body, the immune system recognizes them as foreign and produces antibodies to destroy them.

Characteristics of Antigens

• Usually proteins or complex molecules

• Found on microorganisms or foreign cells

• Stimulate the production of antibodies

• Recognized specifically by the immune system

Sources of Antigens

Antigens may come from:

• Bacteria

• Viruses

• Fungi

• Pollen

• Toxins

• Foreign tissues or transplanted organs

How Antigens Work

1. An antigen enters the body

2. The immune system identifies it as foreign

3. White blood cells activate immune responses

4. Antibodies specific to the antigen are produced

5. The pathogen or harmful substance is destroyed

Antigen-Antibody Reaction

Each antibody matches a specific antigen, similar to a lock-and-key mechanism.

This reaction helps:

• Neutralize pathogens

• Prevent infections

• Remove harmful substances from the body

Importance of Antigens

Antigens are important because they:

• Activate the immune system

• Help the body recognize harmful organisms

• Support immunity and vaccination processes

Antigens in Vaccines

Vaccines contain weakened or harmless forms of antigens that stimulate the immune system to produce antibodies and memory cells without causing severe disease.

This prepares the body for future infections.