Which of the following is not true for polyclonal antibodies?

A. They contain a mixture of antibodies

B. They are raised against purified proteins

C. They can be used to detect targets that differ in only a single antigenic determinant

D. The amounts of antibodies in a polyclonal preparation may vary from one batch to another

B. They are raised against purified proteins

Explanation:

Polyclonal antibodies are those produced as a result of an immune response to an antigen, which generally involves the activation of multiple B cells, all of which address a specific epitope on that antigen. These antibodies are characterized by having different epitope specificities and affinities. Polyclonal antibodies can be obtained from the serum of immunized animals when the antigen of interest stimulates B lymphocytes to produce a diverse range of immunoglobulin specific for that antigen. Such antibodies can be used to detect targets that differ only in a single antigenic determinant and their amount originates from a polyclonal preparation that varies from batch to batch.

As stated earlier, these antibodies are made to be used against antigens and not against a purified protein.