Kochan, Ivan (Baylor University, Dallas, Texas) and Sandra R. Rose. Fate of tubercle bacilli in lipopolysaccharide- and BCG-treated mice. J. Bacteriol. 84:291–294. 1962—The fate of intravenously injected tubercle bacilli in lipopolysaccharide (LPS)- and BCG-treated mice was compared in this study to that in BCG-vaccinated and untreated mice. The potentiality of the treatments in development of “nonspecific immunity” was evaluated by determining numbers of tubercle bacilli in tissue homogenized suspensions rather than by the usually employed survival time of infected animals. The results indicate that during the experimental period the fate of tubercle bacilli of the challenge infection was the same in LPS-treated and heat-killed BCG-treated mice as in the untreated animals. Shortly after infection, the bacillary number increased during a 4-day period; after this time their number declined, reaching about half of the original number by 10 days. The vaccination of animals with live BCG induced good immunity. The same numbers of tubercle bacilli in LPS-and BCG-treated as in normal mice raise doubts as to the efficacy of “nonspecific immunity” in the suppression of bacteria in treated animals.