The fruit fly, or Drosophila, has played a central role in so many important scientific discoveries it is difficult to know where to start with this little insect. In immunology, one of the most important was the discovery of a class of proteins that play a key part of the innate immune system. These proteins are known as the toll-like receptors.
They sit on the surface of “sentinel” cells, such as macrophages and dendritic cells which are first on the scene when microbes have breached the body’s physical barriers, such as the skin or intestinal mucosa. Their function is to quickly recognise the invading microbes as alien and to activate the immune cell responses. Toll-like receptors were identified in mammals in 1997 but the name “toll” derives from the discovery of the detection of a similar gene in drosophila by Christiane Nusslein-Volhard [umlaut over u] and Eric Wieschaus in 1985 when they both shouted out “Das ist ja toll!” when they simultaneously saw an underdeveloped portion of the front side of a fruit fly while looking down the same dual microscope. (“Toll” means “amazing” or “great” in German.) Toll-like receptors, named after the toll gene discovery in Drosophila, are now counted among the key molecules that alert the immune system of mammals to the presence of microbial infections. The first human toll-like receptor was described in 1994 by a team of Japanese researchers, and the first description of their immunological function in mammals came in 1997 from studies by Yale University immunologists Charles Janeway and Ruslan Medzhitov.