Principle of ELISA

ELISA utilizes enzyme-labeled antigens and antibodies to detect biological molecules. Antigens are immobilized in 96-well microtiter plates. A specific capture antibody (primary antibody) is added to the wells and binds to the antigen. An enzyme-coupled detection antibody (secondary antibody) is then added and binds to the primary antibody. Chromogenic substrates for the enzyme are added, yielding a visible color change, thus indicating the presence of the antigen. The color intensity can be measured quantitatively and/or qualitatively to identify the amount of antigen present.