The periodontium of rats submitted to experimental periodontitis and received no treatment (EPD) showed marked immune-staining for both TNF- α (Figure 4B, 4E) and iNOS (Figure 4H, 4K) when compared to the periodontium of the sham group (Figures 4A, 4D, and 4G, 4J, respectively). The gene discussed is TNF; the disease is periodontitis.