Antigen

Definition

An antigen is any substance that induces an immune response in the body, specifically by triggering the production of antibodies. They are typically foreign proteins or polysaccharides found on the surface of pathogens like bacteria and viruses.

5 Must Know Facts For Your Next Test

1. Antigens can be proteins, polysaccharides, lipids, or nucleic acids.
2. They are recognized by specific receptors on immune cells such as B cells and T cells.
3. The epitope is the part of an antigen that is recognized by an antibody.
4. Monoclonal antibodies are derived from a single clone of B cells and are specific to a single epitope.
5. Polyclonal antibodies are produced by different B cell lineages and can bind to multiple epitopes on the same antigen.

Review Questions

• What types of molecules can act as antigens?
• How do monoclonal antibodies differ from polyclonal antibodies in their specificity?
• What part of the antigen is specifically recognized by an antibody?

Related terms

Epitope: The specific part of an antigen that is recognized and bound by an antibody.

B Cell Receptor (BCR): A membrane-bound immunoglobulin molecule on B cells that binds to antigens.

Pathogen: An organism or substance capable of causing disease, often identified by its antigens.