The effect of BCG vaccination on the fate of virulent tubercle bacilli in mice.

Abstract

The protective effect of BCG vaccination against experimental tuberculosis can be demonstrated by a variety of techniques. Most commonly, the differences in resistance between vaccinated and control groups are measured in terms of (a) survival time of the experimental animals following virulent challenge infection; (b) numbers of living bacilli that can be recovered from the various organs; and (c) qualitative and quantitative characteristics of the lesions. While these techniques have been most widely used to measure the immune state, they can be adapted also to the analysis of the mechanisms of immunity. In the present paper, attention will be focused on one particular aspect of this problem, namely, on the fate of the infective bacilli during the very first phase of the challenge infection. Specifically, the experiments to be reported here were designed to determine whether BCG vaccination does enhance the ability of the mouse to destroy the virulent bacilli at the time of infection.