Textbook Problem

Drugs with names that end in “–mab” consist of antibodies, and the research that yields these medications typically begins with mice. A mouse is injected with a molecule or interest: a human cytokine, for example, or a receptor implicated in cancer. The resulting antibody mediated response produces a set of antibodies that recognize different parts or the molecule. B cells are harvested from the mouse’s spleen, fused with cancerous B cells, and then cloned—isolated and cultivated separately. Each of the resulting cell lines produces identical antibodies that bind to one part of the injected molecule. These antibodies are called monoclonal antibodies, and they can be purified and studied for use as drugs.

Monoclonal antibodies can be effective drugs, but only in the immediate term. Antibodies produced by one’s own immune system can last up to about six months in the bloodstream, but monoclonals delivered in passive immunization often last for less than a week. Why the difference?