In an indirect ELISA, what comprises the indicator system for antibody detection?

In an indirect ELISA, the main goal is to detect specific antibodies present in a sample. The indicator system crucial for this detection involves an enzyme-conjugated secondary antibody that binds to the specific antibody being tested. This secondary antibody is linked to an enzyme that catalyzes a reaction with a chromogenic substrate, resulting in a color change that can be measured.

The enzyme-conjugated antibody interacts with the sample containing the target antibodies, amplifying the detection signal. When the chromogenic substrate is introduced, the enzyme catalyzes a reaction that produces a colored product, which is proportional to the amount of specific antibody present. This system of enzyme-conjugated antibody paired with a chromogenic substrate creates a measurable result, making it a fundamental component in the indirect ELISA for antibody detection.

In contrast, using an enzyme-conjugated antigen or substrate without the specific enzyme-linked antibody would not provide the necessary means to detect the antibodies effectively, as the primary goal of indirect ELISA is to identify antibodies rather than antigens.