They are tiny magic bullets that are quietly shaping the lives of millions of patients around the world. Produced in the lab, invisible to the naked eye, relatively few people are aware of these molecules’ existence or where they came from. Yet monoclonal antibodies are contained in six out of ten of the world’s bestselling drugs, helping to treat everything from cancer to heart disease to asthma.

Known as Mabs for short, these molecules are derived from the millions of antibodies the immune system continually makes to fight foreign invaders such as bacteria and viruses. The technique for producing them was first published 40 years ago. It was developed by César Milstein, an Argentinian émigré, and Georges Köhler, a German post-doctoral researcher. They were based at the UK Medical Research Council’s Laboratory of Molecular Biology in Cambridge.

Harnessing the Power of the Immune System

Milstein and Köhler wanted to investigate how the immune system can produce so many different types of antibodies, each capable of specifically targeting one of a near-infinite number of foreign substances that invade the body. This had puzzled scientists ever since the late 19th century, but an answer had proved elusive. Isolating and purifying single antibodies with known targets, out of the billions made by the body, was a challenge.

The two scientists finally solved this problem by immunising a mouse against a particular foreign substance and then fusing antibodies taken from its spleen with a cell associated with myeloma, a cancer that develops in the bone marrow. Their method created a hybrid cell that secreted Mabs. Such cells could be grown indefinitely, in the abdominal cavity of mice or in tissue culture, producing endless quantities of identical antibodies specific to a chosen target. Mabs can be tailored to combat a wide range of conditions.