Networked T cell death by soluble host- and/or pathogen-derived mediators released during Mtb infection may contribute to the T cell lymphopenia observed in patients with active TB disease; furthermore, premature deletion of T cells as they approach the infection site could inhibit the delivery of activating cytokines such as IFN-γ, thus rendering the infected phagocytes incompetent to degrade and clear the pathogen. This evidence concerns the gene IFNG and infection.