TNF and periodontitis: Possible mechanisms include direct stimulation of the tonsils by smoking which increases the production of inflammatory substances (such as interleukin (IL)-17), induces or aggravates inflammation in the tonsils, aggravates other factors such as periodontitis, alters immune responses to commensal bacteria, and activates cholinergic signaling pathways through the production of Tumor necrosis factor (TNF)-α from epidermal cells and nicotinic acetylcholine receptors.