In addition, Ziehl–Neelsen staining revealed that bacilli in both WT and TNFtm/tm mice are less abundant and predominantly confined to granulomas at 4 weeks and 8 weeks post-infection, whereas in TNF−/− mice with the absence of properly defined granulomas the bacilli were dispersed in the tissue and predominantly extracellular (Fig. 4b). The gene discussed is TNF; the disease is infection.