#Id: 4631
#Unit 13. Methods in Biology
Competitive ELISA. In this technique, antibody is first incubated in solution with a sample containing antigen. The antigen-antibody mixture is then added to an antigen coated microtiter well.
The more antigen present in the sample, the less free antibody will be available to bind to the antigen-coated well.
Addition of an enzyme-conjugated secondary antibody (Ab2) specific for the isotype of the primary antibody can be used to determine the amount of primary antibody bound to the well as in an indirect ELISA.
In the competitive assay, however, the higher the concentration of antigen in the original sample, the lower the absorbance.
