As the workhorses of our internal defence system, we owe an enormous debt to antibodies. Responding to external threats such as disease-causing microorganisms, protein antibody molecules are released by specialized immune cells into the blood stream to disarm the threat. Their mode of attack is target recognition: millions of different molecules can be created, each with a different binding site, which can identify distinctive proteins on their specifically assigned foe with pinpoint accuracy.

A long-standing question in the field was how an almost identical-looking collection of antibody proteins can, at the same time, have the capacity to target specifically any one of an almost infinite range of foreign agents – until their structure was solved by the recipients of 1972 Nobel Prize in Physiology or Medicine. Gerald Edelman and Rodney Porter independently took similar approaches to deciphering their structure, both realizing that the best way in which to grasp the finer aspects of such large molecules was to split them into smaller, more manageable pieces. Their deconstruction methods differed. Porter used a protein-cleaving enzyme that fragmented an antibody molecule into its functional subsections. Edelman’s approach destroyed antibody function by using chemicals to break the bridge-like bonds that keep the constituent protein chains together, his procedure relying on the finding that copious quantities of antibodies are produced by cancerous versions of white blood cells.

Edelman’s and Porter’s methods yielded different perspectives of the general antibody structure, which were later combined to provide a more definitive image. Antibodies are composed of two long, heavy protein chains and two identical shorter, light chains, which combine to form three sections that make up a Y-shaped molecule. At both points at the top of the “Y”, a light chain is paired up with a heavy chain to form the unique binding site for each specific target. A third section links the two heavy chains together to form the stem of the “Y”, a region that doesn’t change from one antibody to another, and which is charged with the task of binding several other key components needed to mount a defence against the intended target.