TNF and periodontitis: Studies of periodontal disease suggest a role for the chemokines CCL2 and CCL5 in macrophage migration,40 and cytokines such as TNF-α, IL-1β and IL-6 also contribute to osteoclast activation and inflammatory cell recruitment.41, 42 Our results show that coincident with impaired osteogenesis, IL-1β-treated PDLSCs could induce the chemotaxis of macrophages by expressing CCL2 and CCL5 and producing inflammatory cytokines, which helps to further explain the immunomodulatory effects of PDLSCs in the mediation of immune cells and the pathogenesis of periodontitis.