TRUE BLOOD

One of the most valuable substances in the world has never been replicated. Are we close?

- NICOLA TWILLEY

Blood is in high demand almost everywhere, but its seemingly endless complexity has confounded scientists for decades.

In a pair of fluorescent-lit rooms on both sides of the Atlantic, the guinea pigs awaited their fate. They were not literally guinea pigs. Two were lightly sedated, extremely fluffy white rabbits resting on pee pads; the other was Nick Green, a sixty-four-year-old part-time administrator at the University of Cambridge who reclined, hands clasped atop his patterned sweater, on the starched sheets of a hospital bed. All three were hooked up to machines that provided a readout of their vital signs, and all three were prepared to have a syringe of manufactured blood injected into their veins.

There were, of course, some differences. In their metal cages in Baltimore, the rabbits were pampered with fleece blankets and fresh hay, water, and pellets, which were served in front of a screen that streamed a ten-hour YouTube video titled "Instantly Soothe Anxious Rabbits (Tested)." The video showed an endless sequence of bunnies hopping through meadows and being gently tickled behind the ears. Meanwhile, Green made do with a slightly depressing cafeteria lunch—a cheese-and-pickle sandwich and a shiny red apple—and some chitchat about the weather.

Perhaps more significantly, the rabbits were not in the best of shape. Their pink eyes blinked laboriously; they panted and shivered. Half their blood had been drained from their bodies, sending them into hemorrhagic shock—a disastrous multi-organ shortage of oxygen that, even with prompt resuscitation, frequently proves fatal. Green, on the other hand, was fit and well. A keen cyclist, he'd pedalled that morning into a research facility on the outskirts of Cambridge, and planned to ride into work later that afternoon. “Yes, I am a MAMIL,” he confessed, using the popular British acronym for middle-aged men in Lycra, perched on their expensive bikes.