Blood can both give life and take it away. Consider the history of the blood transfusion, which is the transfer of blood from one living thing into the bloodstream of another.
In the 1660s, several scientists experimented with blood transfusions. Richard Lower had some success transfusing blood between dogs. Then he injected lamb blood into humans, and a patient died. Blood transfusion was outlawed.
In 1818, James Blundell gave a woman blood from her husband. It worked, no problem. But other patients died from transfusions. Decades later, a German named Leonard Landois learned why. When different bloods mix, red blood cells can clump up and even explode. In 1901, American biologist Karl Landsteiner found the reason. Antigens are special markers on germs and other substances. They make your body produce antibodies, proteins that defend against invaders. Some blood has antigens we call A and B, which are harmful to blood that doesn’t have A or B antigens.
Today, doctors test blood for antigens before doing a transfusion. Safe transfusions save countless lives.
