Russian immunologist

Élie Metchnikoff was a pioneer in the field of immunology and won the 1908 Nobel Prize in physiology or medicine for his discoveries of how the body protects itself from disease-causing organisms. Later in life, he became interested in the effects of nutrition on aging and health, which led him to advocate some controversial diet practices.

Metchnikoff, the youngest of five children, was born in the Ukrainian village of Ivanovka on May 16, 1845, to Emilia Nevahovna, daughter of a wealthy writer, and Ilya Ivanovich, an officer of the Imperial Guard in St. Petersburg. He enrolled at the Kharkov Lycee in 1856, where he developed an especially strong interest in biology. At age 16, he published a paper in a Moscow journal criticizing a geology textbook. After graduating from secondary school in 1862, he entered the University of Kharkov, where he completed a four-year program in two years. He also became an advocate of the theory of evolution by natural selection after reading Charles Darwin's On the Origin of Species by Means of Natural Selection.

In 1864, Metchnikoff traveled to Germany to study, where his work with nematodes (a species of worm) led to the surprising conclusion that the organism alternates between sexual and asexual generations. His studies at Kharkov, coupled with his interest in Darwin's theory, convinced him that highly evolved animals should show structural similarities to more primitive animals. He pursued his studies of invertebrates in Naples, Italy, where he collaborated with Russian zoologist Alexander Kovalevsky. They demonstrated the homology (similarity of structure) between the germ layers—embryonic sheets of cells that give rise to specific tissue—in different multicellular animals. For this work, the scientists were awarded the Karl Ernst von Baer Prize.

Metchnikoff was only twenty-two when he received the prize and had a promising career ahead of himself. However, he soon developed severe eye strain, a condition that hampered his work and prevented him from using the microscope for the next fifteen years. Nevertheless, in 1867, he completed his doctorate at the University of St. Petersburg with a thesis on the embryonic development of fish and crustaceans. He taught at the university for the next six years before moving to the University of Odessa on the Black Sea where he studied marine animals.

During the summer of 1880, he spent a vacation on a farm where a beetle infection was destroying crops. In an attempt to curtail the devastation, Metchnikoff injected a fungus from a dead fly into a beetle to see if he could kill the pest. Metchnikoff carried this interest in infection with him when he left Odessa for Italy, following the assassination of Czar Alexander II in 1884. A zoologist up to that point, Metchnikoff began to focus more on pathology, or the study of diseases.

This transformation was due primarily to his study of the larva of the Bipinniara starfish. While studying this larva, which is transparent and can be easily observed under the microscope, Metchnikoff saw special cells surrounding and engulfing foreign bodies, similar to the actions of white blood cells in humans that were present in areas of inflammation. During a similar study of the water flea Daphniae, he observed white blood cells attacking needle-shaped spores that had invaded the insect's body. He called these cells phagocytes, from the Greek word phagein, meaning, to eat.

While scientists thought that human phagocytes merely transported foreign material throughout the body, and therefore spread disease, Metchnikoff realized they performed a protective function. He recognized that the human white blood cells and the starfish phagocytes were embryologically homologous, both being derived from the mesoderm layer of cells. He concluded that the human cells cleared the body of diseasecausing organisms. In 1884, he injected infected blood under the skin of a frog and demonstrated that white blood cells in higher animals served a similar function as those in starfish larvae. The scientific community, however, still did not accept his idea that phagocytic cells fought off infections.

Metchnikoff returned to Odessa in 1886 and became the director of the Bacteriological Institute. He continued his research on phagocytes in animals and pursued vaccines for chicken cholera and sheep anthrax. Hounded by scientists and the press because of his lack of medical training, Metchnikoff fled Russia a year later. A chance meeting with French scientist Louis Pasteur led to a position as the director of a new laboratory at the Pasteur Institute in Paris. There, he continued his study of phagocytosis for the next twenty-eight years.

But conflict with his fellow scientists continued to follow him. Many scientists asserted that antibodies triggered the body's immune response to infection. Metchnikoff accepted the existence of antibodies but insisted that phagocytic cells represented another important arm of the immune system. His work at the Pasteur Institute led to many fundamental discoveries about the immune response, and one of his students, Jules Bordet, contributed important insights into the nature of complement, a system of antimicrobial enzymes triggered by antibodies. Metchnikoff received the Nobel Prize for physiology and medicine in 1908 jointly with Paul Ehrlich for their work in initiating the study of immunology and greatly influencing its development.

Metchnikoff's interest in immunity led to writings on aging and death. His book The Nature of Man, published in 1903, extolled the health virtues of "right living," which for him included consuming large amounts of fermented milk or yogurt made with a Bulgarian bacillus. In fact, his own name became associated with a popular commercial preparation of yogurt, although he received no royalties. With the exception of yogurt, Metchnikoff warned of eating uncooked foods, claiming that the bacteria present on them could cause cancer. Metchnikoff claimed he even plunged bananas into boiling water after unpeeling them and passed his silverware through flames before using it.

On July 15, 1916, after a series of heart attacks, Metchnikoff died in Paris at the age of 71. He was a member of the French Academy of Medicine, the Swedish Medical Society, and the Royal Society of London, from which he received the Copley Medal. He also received an honorary doctorate from Cambridge University.

See also Phagocyte and phagocytosis