Allergy Response to Tuberculosis in Guinea-Pigs Previously Treated with Tuberculin Fractions and Toxin Filtrates.

The basis of these experiments is a study of the so-called Koch phenomenon elaborated by Krause 1 on allergy in experimental tuberculosis. The early anatomical response of the tissues of a susceptible animal inoculated for the first time with tubercle bacilli differs from that of a reinfection. In the susceptible guinea-pig a well circumscribed nodular tubercle will develop slowly after a week or more, without any of the signs of inflammation. Only later, after 3 or more weeks, does redness appear around the tubercle, associated with changes that are indicative of a progressive lesion. At this stage the animal has become allergic, i. e., it begins to react in a new way because of the changes set up in the body by the tubercle bacilli. The susceptibility of the animal has been altered. If such an animal now receives an intracutaneous inoculation of tubercle bacilli, the response by the tissue is rapid and local inflammation occurs. Instead of well localized proliferation, diffuse exudation takes place. The inflammation occurs rapidly and subsides as rapidly, and the nodular tubercle now present retrogresses and may disappear completely. All of these changes are contingent, however, upon moderate dosages of tubercle bacilli.

In the first group of experiments, 5 series of normal guinea pigs, 3 animals in each series, were used. Subcutaneous injections of the different materials were given weekly in increasing doses over a period of 10 weeks, the initial dose ranging from 0.1 to 0.2 cc., and the final dose from 2.0 to 3.5 cc. Four weeks after the last injection, the animals were inoculated intracutaneously with 0.4 mg. of a moderately virulent strain of human tubercle bacilli. One group received tuberculin fractions∗; another, tuberculin fractions and toxin filtrates∗ injected on alternate weeks; a third group received toxin filtrates alone; a fourth, the same toxin filtrate heated for one hour at 75° C.; and the fifth untreated group served as a control.