Clemens von Pirquet (1874-1929), Austrian doctor. Pirquet is best remembered for his discoveries in immunology and bacteriology. In 1906, he described the hypersensitivity displayed by patients who were injected a second time with a vaccine or similar substance that triggered the immune system. He and Bela Schick called this reaction an allergy. This principle led Pirquet to suggest ways to test for tuberculosis, and in 1907 Charles Mantoux used this idea to develop a tuberculosis test using tuberculin. During his career, Pirquet worked in Vienna, at the Johns Hopkins Hospital in the USA, and Breslau in Poland.