Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis whose interaction with the host may lead to a cell-mediated protective immune response. The presence of interferon-γ (IFN-γ) is related to this response. With the purpose of understanding the immunological mechanisms involved in this protection, the lymphoproliferative response, IFN-γ and other cytokines like interleukin , and tumor necrosis factor alpha (TNF-α) Key words: tuberculosis -interleukin-5 -interleukin-10 -tumor necrosis factor alpha -interferon-γ -peripheral blood mononuclear cells Tuberculosis (TB), a chronic infective-contagious disease, is caused by Mycobacterium tuberculosis and remains an important public health problem whose mechanisms related to a protective immunity in humans are not clear. The resurgence of TB has stimulated studies for the development of vaccines, new diagnostic methods and less toxic and more effective drugs for treatment (Laal et al. 1997). The cellular immunity plays an important role in TB healing (Ladel et al. 1997, Torres et al. 1998, Turner et al. 2000, Chackerian et al. 2001). Resistance to mycobacterial infections is conferred by immunological mechanisms mediated by T CD4 + lymphocytes, involving cytokines that increase the microbicide activity of macrophages (Dlugovitzky et al. 2000, Oberholzer et al. 2000. Studies in murine and human models allow differentiating two subpopulations of T CD4 + lymphocytes termed Th1 and Th2, that mediate the protection or the aggravation of the disease (Ladel et al. 1997, Kori et al. 2000. This existing dichotomy between the protective or non-protective immune responses is likely to be correlated with cytokine patterns produced by different subpopulations of lymphocytes during initial surviving stages of the pathogens inside macrophages. Interferon-γ (IFN- γ) acts as a powerful macrophage activator, increasing the molecule expression of the main class II histocompatibility complex and the potentialization of the cell response, including the production of cytokines, nitric oxide, and the increase of the cytolitic activity, with a main role in the Th1 type (Flesh et al. 1995). Studies carried out by Cooper et al. (1993) and Flynn et al. (1993) demonstrated that mice without the IFN-γ gene were not able to fight off the infection caused by M. tuberculosis. In humans, individuals who presented genetic mutations in the receptors for IFN-γ were observed to have had a high susceptibility to acquire infections caused by atypical mycobacteria (Jouanguy et al. 1996), suggesting an important role of IFN-γ in the protective response against TB.Besides the importance of better understanding the immunological mechanisms that may contribute to the healing, it becomes essential to determine markers of healing lesions, once this is currently carried out based on the clinical, radiological, and negative bacterioscopy.In this work, we proposed the in vitro evaluation of IFN-γ levels produced by peripheral blood mononuclear cells (PBMC) after Bacillus Calmette-Guerin (BCG) stimulati...