TNF and infection: The protective mechanisms of cell-mediated immunity (Th1 cells) are required for the resistance during this infection; nevertheless, unbalanced Th1 cells can also orchestrate a deleterious response that can cause tissue damage and fibrosis, since high levels of NO, IFN-γ, and tumor necrosis factor (TNF) have been associated with the pathogenesis of chronic Chagas disease (10–14).