Michael Heidelberger

On his 100th birthday, Michael Heidelberger was asked what it takes to be a successful scientist.

“It’s crucial to keep your eyes and mind open,” he said. “You can’t be a slave to any one idea.” He died three years later, closing the book on more than 70 years of research that – one might argue – helped others live similarly long lives.

Heidelberger, a trained organic chemist, is the father of modern immunology, the medical study of the human immune system. In 1923, he and colleague Oswald T. Avery discovered that the toxins in bacteria responsible for pneumonia are complex polysaccharides – carbohydrate molecules. Using this knowledge, Heidelberger created a vaccine against pneumonia that saved the lives of thousands of soldiers during World War II.

He is also credited with advancements in drugs used to treat infectious diseases ranging from syphilis to African sleeping sickness, a parasitic condition carried by tsetse flies.