Robert Koch (1843?1910), who isolated Mycobacterium tuberculosis in 1882 and proved that it caused tuberculosis, announced at a medical congress in Berlin eight years later that he had developed a substance capable of preventing the growth of the tubercle bacilli, thus arresting the disease. He called this substance ?tuberculin,? while keeping its formulary secret. Actually, it was a glycerin-broth culture he used to grow M. tuberculosis, which he then evaporated to one-tenth its volume at 100° C before filtering. Within days, newspapers around the world announced that Koch had a cure for tuberculosis.
The truth surfaced months later. Tuberculin did not cure tuberculosis, and actually harmed patients who had the advanced disease. When Rudolf Virchow published negative findings about tuberculin in January 1891, Koch felt pressured to reveal its simple preparation. Adulation descended to ridicule, when, besides disappointment over tuberculin, the public learned that the 50-year old Koch was divorcing to marry his teenaged mistress. Speculation swirled that tuberculin had been a hoax to finance the doctor?s sexual escapades.
Koch had noticed that tuberculin injected into the skin produced a reaction spot within 48 hours in subjects who previously had tuberculosis. But this ?Koch phenomenon? was less enticing to him than prospects for a vaccine. While he turned his attention to other things, Viennese pediatrician Clemens von Pirquet, who pioneered hypersensitivity studies of vaccines, believed tuberculin could be a suitable diagnostic tool for presymptomatic tuberculosis, and thus a way to isolate infected people who could spread the disease.
Von Pirquet knew that hypersensitivity was an ?allergy? (a term he coined in 1906) resulting from a second or subsequent exposure to an antigen. He then reported in 1907 how a drop of tuberculin on scarified skin (in the manner of smallpox vaccination) served as a test for tuberculosis.
1. C. von Pirquet, ?Tuberkulindiagnose durch cutane Impfung,? Berliner Klinische Wochenschrift, 44:644?5, 1907.