Jules Bordet, a pioneer in immunology, was born on this day tomorrow in 1870. The Belgian scientist is best known for figuring out how to detect immunity to bacteria or viruses. He discovered that a host organism needs two types of proteins to destroy an invading bacterium. One type, called complement proteins--found in the serum of everyone's blood--helps punch a hole in the membrane of foreign cells, breaking them apart. But only people with immunity to a pathogen have a second type of protein--the antibody--that alerts the complement proteins to the presence of that particular bug.
This observation, published when Bordet was only 25, led to many useful immunological tests, such as the Wassermann test for syphilis, which detects antibodies in the sera of people with the disease. The finding also earned Bordet the Nobel Prize in physiology or medicine in 1919. But he didn't stop there: Before his death in 1960, Bordet developed a vaccine against whooping cough, and did groundbreaking research on how viruses infect bacteria and how blood coagulates.
[Source: Trevor I. Williams, Ed., A Biographical Dictionary of Scientists (John Wiley & Sons, ed. 3, New York, 1982)]