Facts supporting the limited length of the latent period
| No experience on long survival period of bacilli under stressful macrophage-related bactericidal mechanisms (i.e. low pH, presence of ROI or RNI) |
| Dynamic turnover of pulmonary cells restricts latency to a period of months. Bacilli should behave in a dynamic way of constant reactivation |
| Regrowth of bacilli inside the necrotic tissue is nonprobable because of the presence of stressful environmental conditions. It depends on the chance to be phagocytosed again by macrophages in the reabsorbing process of the necrotic tissue |
| Experimental data about “resuscitation” of dormant bacilli, which would be the state adopted in the necrotic zones, do not demonstrate a quick reactivation, limiting the percentage of bacilli able to regrow before being removed by the macrophage turnover |
| Bacillary survival inside the encapsulated or calcified lesions is restricted |
| Estimated immunity (15–20 yrs) generated after M. tuberculosis infection ensures a prolonged period of protection against bacillary regrowth |
| Data from chemoprophylaxis trials monitoring reactivation after infection in control groups revealed a progression to a nonexistent probability after 8 yrs |
ROI: radical oxygen intermediates; RNI: radical nitrogen intermediates; M. tuberculosis: Mycobacterium tuberculosis