In the initial steps of periodontal disease, gingival epithelial cells defend against bacterial infection by secreting cytokines such as interleukin (IL)-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and monocyte chemotactic protein (MCP-1) from gingival tissues to induce the migration of immune cells into inflammation sites [45–47]. The gene discussed is CCL2; the disease is bacterial infectious disease.