Indirect ELISA is a two-step ELISA which involves two binding process of primary antibody and labeled secondary antibody. The primary antibody is incubated with the antigen followed by the incubation with the secondary antibody. However, this may lead to nonspecific signals because of cross-reaction that the secondary antibody may bring about.
1. Micro-well plates are incubated with antigens, washed up and blocked with BSA.
2. Samples with antibodies are added and washed.
3. Enzyme linked secondary antibody are added and washed.
4. A substrate is added, and enzymes on the antibody elicit a chromogenic or fluorescent signal.