Polymorphonuclear neutrophil leukocyte(PMN) is an important member of the human immune cells. Recent years, the recognition of the PMN function and the relationship between PMN and periodontitis have been updated. Besides the pathogens killing and phagocytosis, PMN also play an important role in immunoregulation and proresolving. The main-taining of PMN homeostasis is an intricate process and the precondition of defense function, which involves activation, adhe- sion, recruitment, apoptosis and efferocytosis. The regulatory mechanism of PMN homeostasis called neutrophil rheostat, it works through several cytokines and cells. Any factors that break the homeostasis will result in the damage of host immunity, and may relate to the occurrence of periodontitis. Moreover, PMN dysfunction, because of host factors or microorganism factors, is closely related to periodontitis, especially those associated with systemic diseases and gene defect.
