The human immune response to tuberculosis (TB) is especially mediated by T CD4(+)lymphocytes. However, more studies are needed in order to understand the exact role of each cytokine in the mechanisms for cures. In this article, our aim was to analyze the production of TNF-alpha, IL-10, and IFN-gamma in peripheral blood mononuclear cells (PBMCs) among the household contacts of common primary TB cases, with or without histories of active TB infection, who were negative to parasitological and HIV tests. In order to characterize the cytokine production, PBMCs from these groups were stimulated with whole-protein extract of M. tuberculosis (WPE) antigen (rAgTb) for 24 and 48 hr. The culture supernatants were collected and IFN-gamma, TNF-alpha, and IL-10 were assayed using capture ELISA. There were no statistical differences between primary TB cases and their household contacts with or without previous histories of lung TB. Our results suggest that T memory cells, T regulatory cells, and the Th1/Th2 dichotomy may be responsible for the results described in this article. Further studies are currently underway.2050-01-01