Antigen

Definition

An antigen is any substance that triggers an immune response by being recognized as foreign by the immune system. Antigens can be proteins, polysaccharides, lipids, or nucleic acids.

5 Must Know Facts For Your Next Test

1. Antigens are typically found on the surface of pathogens such as bacteria and viruses.
2. The body recognizes antigens through specific receptors on B-cells and T-cells.
3. Each antigen has distinct molecular structures called epitopes that are specifically recognized by antibodies.
4. Vaccines work by introducing antigens to the body to stimulate an adaptive immune response without causing disease.
5. Antigen presentation is a crucial process where antigen-presenting cells display antigens to T-cells, initiating an immune response.

Review Questions

• What types of molecules can function as antigens?
• How do B-cells and T-cells recognize antigens?
• Why are antigens important in the development of vaccines?

Related terms

Antibody: A protein produced by B-cells that binds specifically to an antigen.

Pathogen: An organism or substance capable of causing disease.

Epitope: The specific part of an antigen that is recognized and bound by an antibody or receptor on a lymphocyte.