Every epic tale needs a hero. Ours is 12 microns tall and lives for a matter of hours; it’s called a neutrophil and your life depends on it. Don’t be deceived by its tiny stature and minuscule lifespan; this cell can capture bubonic plague in a web of its own DNA, spew out enzymes to digest anthrax and die in a kamikaze blaze of microbe-massacring glory. The neutrophil is a key soldier in an eternal war between our bodies and the legions of bacteria, viruses, fungi and parasites that surround us. From having sex to cleaning the kitchen sink, everything we do exposes us to millions of potential invaders. Yet we are safe. Most of the time these invaders’ attempts are thwarted. This is because the human body is like an exceedingly well-fortified castle, defended by billions of soldiers. Some live for less than a day, others remember battles for years, but all are essential in protecting us. This is the hidden army that we all have inside of us, and I’d like to reveal its myriad of miracles and secrets to you.
Our adventure tour will begin with a jaunt through our key defences, which include tears, snot, stomach acid and a cast of killer cells. Drawing on everything from the history of medicine to cutting-edge science, we’ll explore the incredible arsenal that lives within us and how it kills off a plethora of diseases, from the common cold to the plague. Next we’ll rattle through the past, present and future of organ transplants – from the first heart transplant to lab-grown vaginas – and the vital role the immune system plays in their success or failure. While organ transplants are needed by very few of us, the truth is every single one of us is dependent on foreign cells to thrive. This will be our focus in ‘Outnumbered’ (Chapter 5) as we’ll unveil the emerging evidence on the immune system’s relationship with the body’s billions of resident bacteria.
We’ll follow this dirty revelation with some sexy science looking at the role of the immune system in our brief encounters, and maybe even love, as we dance the ‘Immunological Tango’ (Chapter 6). The chapter that follows, appropriately, will cover pregnancy. Having grown my own cutie of a parasite while writing this book, this chapter is particularly close to my heart as it tells the tale of how the immune system allows, and actually encourages, a baby to thrive, despite being a foreign invader.