Describe Direct and Indirect protein detection systems work

Describe how the direct and indirect protein detection systems work

The direct protein detection system is when the antibody used to bind to the protein is labeled, for example with a fluorophore. Because it's the primary antibody that binds directly to the protein, that antibody is always specific for that protein.
The indirect protein detection system is when two antibodies are used; the primary antibody which binds to the protein and a secondary antibody that is labeled and binds to the primary antibody. The primary antibody is specific for that protein, but the secondary antibody is not as it only needs to bind on the primary antibody. More secondary antibodies can bind on the primary antibody, amplifying that way the signal of the label used.