Structural Biochemistry/Proteins/Preparation of Polyclonal Antibody
An antibody (which is a protein itself), is also called an immunoglobulin. It is synthesized by an animal’s body when there is a foreign substance (called an antigen). The synthesis of antibodies has high and specific affinities. An antibody can recognize a specific group or cluster of amino acids on a specific molecule (called an antigenic determinant or epitope).
To collect antibodies that recognize a specific protein, a protein is injected once into a rabbit, then a second time about three weeks later. The protein will then stimulate the reproduction of cells and produce antibodies that recognize it. When the blood is taken from the immunized rabbit several weeks later, it is centrifuged to separate the blood cells from the supernatant. Antibodies can be found in the supernatant (also called the serum) to all the antigens the rabbit was exposed to. Only some of them will actually be antibodies to the protein that was originally injected. The indication that cells produce many different antibodies that each recognizes a different surface feature of the same antigen means that the antibodies are heterogeneous, or polyclonal.