Human immune cells — in mice
In 1796, English physician Edward Jenner decided to investigate a tale he had often heard — that milkmaids infected with cowpox became immune to smallpox, a much more dangerous affliction. To test this theory, Jenner inoculated an eight-year-old boy with pus from the blisters of a milkmaid who had caught cowpox. Two months later, Jenner injected the boy with material from a smallpox lesion. The boy did not become ill, nor did the 22 people on whom Jenner later performed the same procedure.Jenner had just made one of the most significant discoveries in medical history — a vaccine against smallpox, one of the greatest scourges humans have faced. But, his methodology would not make it past the ethical review boards that now govern research on human subjects.Today, scientists testing experimental vaccines usually rely on laboratory experiments, measuring the immune responses of cells grown in Petri dishes, or animal studies, which...