ANTIGEN IS A SUBSTANCE OR PART OF A SUBSTANCE THAT STIMULATES AN IMMUNE RESPONSE AND REACTS WITH IMMUNE CELLS OR THEIR PRODUCTS, SUCH AS ANTIBODIES.
The immune system targets antigens. Antigen is an “antibody-generating substance” (living or nonliving); a substance that stimulates an immune response. Generally antigens are large protein or polysaccharide molecules.
Antigens present in a person’s body usually provoke no response. However, when foreign antigens enter the body, they often initiate an immune response which leads to the production of antibodies.
ANTIBODY IS A PROTEIN THAT REACTS TO A SPECIFIC ANTIGEN.
Antibodies are Y-shaped molecules. Antibody is a protein molecule released by a B cell or a plasma cell that binds to a specific antigen. An antibody inactivates or destroys toxins.
Antibodies are of following classes:
IgA, IgD, IgE, IgG and IgM