Jules Hoffmann

Hoffmann discovered that the Toll receptor in Drosophila fruit flies is essential for activating the innate immune response against fungal and bacterial infections. In a landmark 1996 study, his team at the CNRS Institute in Strasbourg showed that fruit flies with mutated Toll genes died rapidly after fungal infection. This was the first demonstration that the innate immune system uses specific receptors to detect pathogens.

Hoffmann's Drosophila Toll work inspired the identification of Toll-like receptors (TLRs) in mammals by Bruce Beutler, who found that mouse TLR4 recognizes bacterial lipopolysaccharide (LPS). Together, these discoveries showed that innate immunity—an ancient, evolutionarily conserved system—is the first line of defense shared from insects to humans. The finding fundamentally changed immunology by showing innate immunity is not nonspecific but uses defined molecular sensors.

Hoffmann shared the 2011 Nobel Prize in Physiology or Medicine with Bruce Beutler of the Scripps Research Institute and Ralph Steinman of Rockefeller University. Beutler was recognized for discovering that TLR4 activates innate immunity in mammals, while Steinman was honored for discovering the role of dendritic cells in adaptive immunity. Steinman passed away three days before the announcement, and the prize was awarded posthumously.

Hoffmann used the fruit fly Drosophila melanogaster as his primary model organism, studying its antimicrobial defense mechanisms for years before the Toll breakthrough. Drosophila lacks adaptive immunity, relying entirely on innate defenses, which made it an ideal system to study how organisms detect and respond to infections without antibodies. His lab identified antimicrobial peptides produced by fruit flies in response to different types of pathogens.