Tuberculosis once again occupies a special position in the areas of
infec- tious diseases and microbiology. This disease has been important
to mankind since even before biblical times. Tuberculosis has been a
major cause of morbidity and mortality in humans, especially in highly
ur- banized Europe, until a few decades ago. Indeed, this disease became
a center of many novels, plays, and operas, since it appeared to be
quite popular to have the heroine dying of "consumption. " Most
importantly, tuberculosis also became the focus of attention for many
investigations during the 19th and even the 20th centuries. Major
advances were made in the areas of isolation and identification of M.
tuberculosis and related microorganisms. The discovery, by Robert Koch,
that tuberculosis was caused by an infectious agent revolutionized our
thinking about dis- eases. Koch's postulates were developed with
tuberculosis in mind and became a focal point for many advances in
microbiology and medicine. Studies with mycobacteria as a central focus
have also led to revolu- tionary new concepts about immunology in
general. Koch himself showed that those exposed to M. tuberculosis
develop a skin hypersen- sitivity or allergy to the microorganism's
antigens, an observation which was the starting point for many important
developments. Indeed, imme- diate-type hypersensitivity and atopic or
IgE-mediated allergy were de- fined in relation to the delayed-type
cutaneous hypersensitivity evi- denced with the tubercle bacillus.