Immunochemical techniques have been in use for many years with
early examples of bacterial strain typing dating back to the 1940s.
The basis for the science is the exquisite elegance of the
mammalian immune system with its ability to recognize foreign
proteins and to manufacture antibody m- ecules that strongly bind
to the substances that elicited them. Not only are potentially
harmful pathogens and toxins recognized by the immune system, but
the system can be persuaded to manufacture antibodies to an
astonishing array of substances. In the early days of this science,
all antibodies for investigative work were produced by immunizing
mammals with the substance of interest, followed by regular donor
bleeds that yielded antisera. Serum produced in this way yields
heterogenic populations of antibody molecules recognizing different
epitopes on the target protein, which may be adequate for its
intended p- poses, but can also cause problems of crossreactivity.
In 1975, Kohler and Milstein reported that spleen cells from immune
donor animals could be immortalized, cloned from single cells, and
grown in continuous culture.