Polyclonal antibody recognizes several epitopes on the target
protein while monoclonal antibody recognizes only single epitope.
Sometimes, monoclonal antibodies are not able to precipitate the
antigen because the epitope might need to be exposed on the surface
of the antigen to be recognized by the antibody. Since the epitope
might be hidden and it's a single epitope that is recognized by the
monoclonal antibody, the propability of the antibody to reconize
the epitope is lower compared with the polyclonal antibody that
recognizes several epitopes on the target protein.