Question

What is an antigen?

Options

• A protective chemical produced in response to foreign substances

• Any foreign substance capable of stimulating an immune response

• A barrier formed by skin and mucous membranes

• A type of white blood cell that fights infections

Answer 1

An antigen is defined as any foreign substance capable of stimulating an immune response. Antigens can be proteins, polysaccharides, or other molecules on the surface of pathogens or foreign substances that trigger the immune system to mount a defensive response.