Which of the Following Best Describes What an Antigen Is

Question

Which of the following best describes what an antigen is?
A) a protein in the immune system that is used to identify potential pathogens
B) a molecule, such as a polypeptide or carbohydrate, that initiates a response from the immune system
C) a molecule that is used during an immune response to enhance the binding of antibodies to damaged cells
D) all of the above

Accepted Answer

An antigen is a molecule, such as a polypeptide or carbohydrate, that initiates a response from the immune system. It is typically a foreign substance that elicits an immune response, but can also be a self-antigen that triggers an autoimmune response. Antigens are recognized by the immune system based on their unique features or epitopes.