Centenary of the death of Elie Metchnikoff: a visionary and an outstanding team leader.

Elie Metchnikoff passed away on July 15th, 1916. He is considered to be the father of phagocytes, cellular innate immunity, probiotics, and gerontology. In all of these fields, he was a visionary. To achieve such a notability and produce so many masterpieces, Metchnikoff used more than 30 animal species to support his findings, and his pasteurian laboratory published more than 200 papers in the Annales de l'Institut Pasteur. As a wonderful team leader and a great mentor, during his 28 years at Institut Pasteur, he welcomed and supervised more than 100 young trainees. Trained as an embryologist, he contributed to the birth of immunology and to the understanding of physiology and pathology. Indeed, Metchnikoff and his team investigated inflammation in guinea pigs, rats, frogs; studied infectious diseases in monkeys, caimans, geese; investigated aging in parrots, dogs, humans; proposed hypotheses to understand age-associated senility using rabbits and humans; developed germ free tadpoles, flies, chicks; studied the gut flora in bats, horses, birds, humans; and popularized the use of probiotics as a tool to delay the deleterious effects of toxic compounds derived from putrefactive gut bacteria. He was also a philosopher and penned essays on human disharmony and on pessimism and optimism.