It describes the history of immunology with the discovery of the principle of graft rejection by Peter Medawar in the 1950s, and the way the body distinguishes self from not-self via natural killer cells.

[5] The book's context is the history of immunology, from the earliest questioning about why people become ill and why some may recover, to the 19th century pioneers who demonstrated that bacteria caused many diseases.

In the 20th century where, slowly at first but at an accelerating pace, biologists started to build an understanding of the genetic basis of variation and natural selection, and alongside that, the foundations of scientific medicine, including immunology.

It’s about brilliant insights and lucky guesses; the glory of being proved right and the paralysing fear of getting it wrong; the passion for cures and the lust for Nobels.

In part 1, Davis describes the history of research into biological compatibility, starting with the story of Peter Medawar's life and discoveries in graft rejection.

He tours the history of medicine from Hippocrates to the 19th century pioneers Louis Pasteur and Robert Koch, and Frank Macfarlane Burnet's concept of the immune system's ability to discriminate self from non-self.

He explains how advances in understanding of immunity, from Karl Landsteiner's discovery of the ABO blood group system onwards, permit organ transplants to take place.

[8] Mark Viney, reviewing the book in the New Scientist, comments that Davis covers human compatibility genes well, but that he should have gone into more detail on the different systems in other organisms.

[9] The science writer Peter Forbes, writing in The Guardian, notes that when Watson and Crick cracked the genetic code in 1953, it seemed that medicine would instantly profit: but half a century went by before the genome was decoded, and 98% of it seemed at first glance to be junk DNA.

Forbes notes that Davis does not mention that most of the genetic differences between humans and chimpanzees are to do with the immune system and brain development: perhaps (he suggests) these are connected.

[11] Emily Banham, reviewing the book for Nature, notes that compatibility genes lie at the heart of our immune systems, playing a part in the success of skin grafts, pregnancy, and more.