Q.Differentiate between antigen and antibody.
An antigen is a foreign substance that triggers an immune response; an antibody is the protective glycoprotein the immune system produces in response to that antigen, and which binds specifically to it.
Step 1. An antigen is defined as any foreign substance invading the body that is capable of stimulating an immune response.
Step 2. An antibody is defined as the protective chemical (a glycoprotein/immunoglobulin) produced by immune cells (plasma cells) specifically in response to that antigen.
Step 3. Structurally and functionally they are opposites within the same interaction: the antigen carries the antigenic determinant (epitope) that is recognised, while the antibody carries the matching antigen-binding site (paratope) that does the recognising, the two combining to form an antigen-antibody complex.
Step 4. In short, the antigen is the trigger/target, and the antibody is the immune system's specific response to it.
Antigen = the foreign, response-triggering substance; Antibody = the specific protective molecule produced against it
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