The Hidden History of Tuberculin

Robert Koch was an eminence on Tuberculosis and a german hero worldwide since he discovered and described the ethiologic cause of the white plague. Soon afterwards, he devoted his work to study the effect of inoculating M.tuberculosis bacilli (Mtb) to guinea pigs, either healthy or already infected. From his experiments, as reported by himself, he learnt the infection was able to develop protection against reinfection in some extent and that using small doses of dead bacilli could help to heal the tuberculous lesions in the infected animals, while large doses could kill them. The 4th of July, 1890, during the International Medical Congress in Berlin, he announced he might have found a cure, and pointed out it should not be used in severe cases as it could do more harm than good. However, tuberculosis was one of the main causes of death at that moment, and the word of Koch’s finding its cure rapidly spread. Many physicians from all over the world traveled to Berlin to learn how to use the new remedy, called tuberculin for being obtained from Mtb bacilli, as Sir Conan Doyle did himself. Koch, probably scared of the great expectancy generated by his cure still not too well-known, decided to write a manuscript entitled “A further report on a remedy for tuberculosis“ (Koch 1890), which was published on midNovember of the same year. With this paper, he intended to clarify and to give a review of the subject, in order to avoid the public to get distorted knowledge on the remedy proposed by him. In the manuscript, he tried to explain why tuberculin worked: he believed the treatment was able to destroy the necrotic tissue of the tuberculous lesions, and this was the cause for the bacilli to die subsequently. But still more important, he cautioned about the fact of existing reactions following the inoculation of tuberculin, which severity depended on the patients and their previous illness status, and suggested it should be applied as early as possible to obtain a positive outcome (Koch 1890).