Accumulating evidence indicates that infiltration by proinflammatory monocytes impacts the properties of tissue macrophages.41 These macrophages could participate in the progression of periodontitis by releasing inflammatory cytokines such as IL-1β, IL-6, and TNF-α.42,43 CD45+F4/80+ cells are considered macrophages in the periodontium.42,43 Hence, we used flow cytometry to isolate CD45+F4/80+ cells from the periodontal tissues of the experimental mice on day 28 after ligature removal. The gene discussed is TNF; the disease is periodontitis.