What is defined as an antigen?

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Multiple Choice

What is defined as an antigen?

Explanation:
An antigen is any substance that the immune system recognizes as foreign and that can trigger an immune response. It doesn’t have to be a whole pathogen; it can be a piece of a protein or polysaccharide on a pathogen, a toxin, or other foreign molecules that the body identifies as non-self. An antibody, by contrast, is the protein produced by the immune system to bind to antigens. A virus is a type of foreign invader that can carry antigens, but the term antigen refers to the specific substance that elicits the immune response, not the invader itself. An enzyme is a different kind of protein that speeds up chemical reactions and is not defined by being recognized as foreign. So the best description is a substance identified as foreign by the body that can provoke an immune reaction.

An antigen is any substance that the immune system recognizes as foreign and that can trigger an immune response. It doesn’t have to be a whole pathogen; it can be a piece of a protein or polysaccharide on a pathogen, a toxin, or other foreign molecules that the body identifies as non-self. An antibody, by contrast, is the protein produced by the immune system to bind to antigens. A virus is a type of foreign invader that can carry antigens, but the term antigen refers to the specific substance that elicits the immune response, not the invader itself. An enzyme is a different kind of protein that speeds up chemical reactions and is not defined by being recognized as foreign. So the best description is a substance identified as foreign by the body that can provoke an immune reaction.

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