A wide variety of labeled secondary antibodies are available commercially.
Versatile because many primary antibodies can be made in one species and the same labeled secondary antibody can be used for detection.
Maximum immunoreactivity of the primary antibody is retained because it is not labeled.
Sensitivity is increased because each primary antibody contains several epitopes that can be bound by the labeled secondary antibody, allowing for signal amplification.
Different visualization markers can be used with the same primary antibody.