Douglas Fearon is a medical immunologist who uncovered the link between innate — natural — and adaptive, or acquired, responses of our body’s immune system. Douglas was able to show that this connection is mediated through the influence of an immune system protein known as complement component 3 (C3).

The immune system relies on both an immediate, non-specific, response, provided by the primitive programming of cells that originate in bone marrow to recognise and react to foreign pathogens, and a more sophisticated system of lymphatic cells that can learn from prior infections. The interaction of both systems enables a rapid response to past infections without triggering an overly aggressive response or allergies.

Douglas discovered that the innate immune system activates C3 proteins in response to vaccination or infection by attaching them to antigens that subsequently stimulate antibody production. C3 also supports ‘immunological memory’, coding defence responses into the adaptive system to build long-term immunity. Douglas found that antigens primed with C3 are around 10,000 times more likely to recognise and respond to past infections.