ABSTRACT
Epidemiological evidence suggests that protective immunity against Mycobacterium tuberculosis exists in most exposed humans. The proportion of nonimmunocompromised individuals who undergo primary infection or reactivation disease following M. tuberculosis infection is low. Only 5% to 10% of M. tuberculosis-infected individuals develop tuberculosis (TB) disease during their lifetime (Fig. 1) (1,2). The study of human immunity to M. tuberculosis infection is critical to the understanding of the mechanisms that contain the initial tuberculous focus and maintain clinical latency. Such studies validate basic concepts established in animal models and are required because differences are apparent between experimental models in cell function, effector molecules, and disease expression. Immunological markers of protection in humans also serve as desirable end points for the study of new antituberculous vaccines and new vaccine delivery strategies and as readouts for adjuvant immunotherapies.
