Which of the following best describes an antigen?

• A. A protein produced by B cells to neutralize pathogens
• B. A chemical signal that attracts immune cells to the site of infection
• C. A molecule that can be recognized by the immune system and elicit an immune response
• D. A type of white blood cell involved in phagocytosis

Answer: (C)

Verified step by step guidance

1. Understand the role of an antigen in the immune system: An antigen is a substance that the immune system can recognize as foreign or non-self.
2. Recall that antigens are typically molecules, often proteins or polysaccharides, found on the surface of pathogens or foreign particles.
3. Recognize that the primary function of an antigen is to elicit an immune response, meaning it triggers the activation of immune cells.
4. Differentiate antigens from other immune components: for example, antibodies are proteins produced by B cells to neutralize antigens, not antigens themselves.
5. Conclude that the best description of an antigen is 'a molecule that can be recognized by the immune system and elicit an immune response.'