ABSTRACT

ELISA A sandwich ELISA can be used to detect and quantify the amount of a specific protein antigen in a sample. The antibody is bound to an inert polymer support, then exposed to the sample. Unbound protein is washed away and a second antibody that reacts with the antigen at a different epitope is added. The second antibody used is one that is fluorescently labeled or has an enzyme attached to it that converts a colorless substrate into a colored product. The amount of second antibody bound, and hence the amount of protein antigen present in the original sample, is determined by quantification of the intensity of color or fluorescence produced. An indirect ELISA, in which the antigen is bound to an inert polymer, can be used to detect the presence in a sample of an antibody against the antigen.