Which statement correctly describes Indirect ELISA?

Which statement correctly describes Indirect ELISA?

• A. It uses a conjugated primary antibody for direct detection.
• B. It includes an additional amplification step to detect antibodies in a sample.
• C. It measures enzyme activity of the target enzyme.
• D. It directly detects the antigen without antibody involvement.

Answer: (B)

Indirect ELISA relies on signal amplification using a secondary antibody. After the plate is coated with antigen, a primary antibody from the sample binds to that antigen. Then an enzyme‑conjugated secondary antibody recognizes and binds to the primary antibody. The enzyme on the secondary antibody converts a substrate to a detectable signal, and because multiple secondary antibodies can attach to one primary antibody, the signal is amplified. This increased sensitivity comes from the use of a secondary antibody rather than labeling the primary antibody itself. It doesn’t measure the target enzyme’s activity or directly detect the antigen without involving antibodies, and it relies on the antibody‑mediated detection step rather than a single labeled primary antibody.

Indirect ELISA relies on signal amplification using a secondary antibody. After the plate is coated with antigen, a primary antibody from the sample binds to that antigen. Then an enzyme‑conjugated secondary antibody recognizes and binds to the primary antibody. The enzyme on the secondary antibody converts a substrate to a detectable signal, and because multiple secondary antibodies can attach to one primary antibody, the signal is amplified. This increased sensitivity comes from the use of a secondary antibody rather than labeling the primary antibody itself. It doesn’t measure the target enzyme’s activity or directly detect the antigen without involving antibodies, and it relies on the antibody‑mediated detection step rather than a single labeled primary antibody.