Antituberculous immunity in mice vaccinated with killed tubercle bacilli.

The resistance of white mice to tuberculous infection could be increased by preliminary vaccination with small amounts of tubercle bacilli killed by contact with 2 per cent phenol. Vaccine prepared from a variant strain of human tubercle bacilli unable to multiply in vivo (H37Ra) proved as active as vaccines prepared from either virulent or attenuated strains. The immunity induced by phenol-killed bacilli persisted for several weeks.

Antituberculous immunity induced in mice by vaccination with living cultures of attenuated tubercle bacilli.

The immunity induced in mice by vaccination with living attenuated cultures of tubercle bacilli was measured by two criteria. (a) Increase in survival time of the vaccinated animals after infection with a dose of virulent bacilli sufficient to kill all the unvaccinated controls within 10 to 20 days. (b) Difference in the number of living bacilli recovered from the spleen and lungs of vaccinated and normal animals infected with a small dose of virulent bacilli.

Multiplication and survival of tubercle bacilli in the organs of mice.

Cultures of tubercle bacilli (typical bovine and human strains) known to differ in the severity of the lesions they induce in experimental animals, were injected in various doses into the cerebrum, peritoneal cavity, or blood stream of mice. Quantitative determinations of the numbers of living bacilli present in the tissues at different intervals of time after infection led to the following classification of the cultures tested:- (a) Certain well known variant forms of tubercle bacilli were found to be unable to multiply in vivo, although they could survive for many weeks in the tissues of mice. These organisms proved to be truly avirulent.

THE EFFECT OF TUBERCLE BACILLI ON THE POLYMORPHONUCLEAR LEUCOCYTES OF NORMAL ANIMALS.

A description is given of a slide cell whereby the rate of migration of very small amounts of leucocytes can be followed and measured. The migration of polymorphonuclear leucocytes was found to be inhibited by virulent tubercle bacilli pathogenic for the class of animal (mammal or bird) from which the leucocytes were obtained; it was not affected by the avirulent variants of these microorganisms, or by bacilli pathogenic for animals of the other class. Tests failed to disclose that the inhibition of leucocytic migration resulted from any gross damage caused by the bacilli to the leucocytes.