Enzyme-linked immunosorbent assays are assays in which both and reactions are utilized.

Enzyme-linked Immunosorbent Assays are assays in which both antigen and antibody reactions are utilized. It is an enzyme immunoassay in which a specific antigen with unknown amount is immobilized on the ELISA plate and a specific enzyme is added which is conjugated with an enzyme.

This enzyme is responsible for reacting with the substrate and on the reaction substrate gives a specific color. So higher the amount of antibody bounded with antigen higher will be the production of color.

In indirect ELISA two antibodies are used and the second antibody is conjugated with an enzyme and binds specifically with primary antibody. Primary antibody is already bonded with antigen. In indirect ELISA nonspecific binding is restricted so detection is more accurate.