Infection with periodontal bacteria and their metabolites triggers an increased expression of the inflammatory mediator prostaglandin E2 (PGE2), in addition to pro-inflammatory cytokines, such as interleukin (IL)1β, IL6, and tumor necrosis factor (TNF)α3,4, and chemokines such as IL8 and C-C motif chemokine ligand 5 (CCL5)5. The gene discussed is CCL5; the disease is infection.