Secondary antibodies are designed to recognize and bind to primary antibodies in a number of immunoassays. Using secondary antibodies in immunoassays offers several advantages.    

• The signal amplification resulting from multiple secondary antibodies binding to a single primary antibody attracts additional reporter molecules to the antibody-antigen complex, which increases sensitivity.
• A given secondary antibody is able to bind to any primary antibody of the same type and host species, which makes secondary antibodies more versatile.
• Secondary antibodies expand conjugate options by offering extended access to a wider range of probes and increasing flexibility in assay design.
• Prevents interference with the paratope or the primary antibody’s antigen-binding site and preserves the primary antibody’s activity. 
• Secondary antibodies enable multiplexing or multi-labeling in experiments.