The resurgence of tuberculosis as one of the most important infectious diseases to affect mankind came after the illusion that the disease was under control and would be eradicated before the end of the 20th Century. Over the last 10 years, in association with American and European research centers, our group at the Universidade Federal do Rio de Janeiro has been dedicated to investigating the pathogenic mechanisms involved in pulmonary tuberculosis. Due to its frequency and role in transmission, pulmonary tuberculosis is the most serious form of the disease. Our hypothesis is that the establishment of latent infection and its progression to active disease depend on an imbalance between activating and deactivating cytokines at the disease site. Despite the presence of protective mechanisms such as the macrophage expression of phenotypes (denoting cellular and molecular activation of agents involved in protection, such as nitric oxide and interferon-ã), tuberculosis progresses. A possible explanation for this is the concomitant presence at the site of infection of molecules such as interleukin-10 and TGF-â, which are able to deactivate previously activated macrophages. Recent data suggest that mycobacteria secrete proteins capable of inducing interleukin-10, thus contributing to overcoming host protective mechanisms. Susceptible individuals would be more able to produce larger amounts of these molecules due to genetic polymorphisms that facilitate interleukin-10 production at infection onset. The understanding of these mechanisms could advance the prevention and discovery of new therapeutic targets for the control of tuberculosis.

Keywords: Tuberculosis/ethiology. Tuberculosis pulmonary/pathology.