Immunoaffinity chromatography (IAC) harnesses the specificity and avidity of the interaction between an antigen and its antibody to purify the antigen. The technique may be used with either polyclonal or monoclonal antibodies (MAb) (1), but MAbs are preferable for a number of reasons. Polyclonal sera are never specific for a single antibody but reflect the variety of immunological challenges sustained by an animal since birth. Furthermore, the best polyclonal sera are generated using highly purified antigen, so if a purification method already exists, why raise sera to develop a second purification method? Perhaps the main disadvantage of polyclonal sera lies in the wide range of avidity of antibodies they contain; although this ensures that such antibodies will bind their antigen, the dissociation of the antigen-antibody complex may prove impossible using conditions that retain the activity of both.