It is traditionally considered that the development of Latent Tuberculosis Infection (LTBI) is due to the M. tuberculosis ability to develop a dormancy state within well-structured lesions (granulomas), which can remain in the lung of the host even for life. A new original hypothesis has been developed in the Experimental Tuberculosis Unit based on scientific evidence that take into account the idea that a lesion cannot be held forever, because the host tends to remove any lesion in order to rebuild the original parenchyma, in a healing process. Even if M. tuberculosis can remain in a dormant/non-replicating state for a long period, this is an important but not sufficient factor to explain the LTBI. The Dynamic Hypothesis tries to explain the existence of LTBI in spite of the healing process that could remove it by a constant reinfection of the host's tissue. While the "Static" view defends the induction of active TB after the reactivation of the bacilli from and old lesion; while the "Dynamic" view wants to demonstrate that there is a constant induction of new granulomas. In case one of these new lesions takes place in the upper lobe privileged zone, the possibility to induce a cavity would appear, developing an active Tuberculosis (TB).

Inclusion Criteria:

• being at least 18 years old
• to be M.tuberculosis infected (diagnosed by a positive TST with or without a positive result in the QuantiFeron-TB-Gold In tube assay)

Exclusion Criteria:

• active TB
• individuals not willing to participate in the study and or not willing to sign the informed consent form
• individuals not able to decide their participation in the study

Latent Tuberculosis Infected people