The science of licking your wounds: Function of oxidants in the innate immune system

Animals often lick their wounds to promote healing. Saliva is thought to have healing properties due to it containing many agents that have antimicrobial properties. A number of these components make up the innate immune system's oxidant generating network. One of these components is the saliva peroxidase also known as lactoperoxidase (LPO). LPO utilizes hydrogen peroxide (H2O2) and the pseudohalide thiocyanate (-SCN) to generate a broad-spectrum antimicrobial oxidant hypothiocyanous acid (HOSCN). HOSCN has antimicrobial activity against viruses, fungi, and bacteria. Although saliva contains the highest levels of -SCN and HOSCN in the body, this network operates in all extracellular fluids in the body including the blood, tears, nasal and lung fluids, gastric fluid, milk and semen. Another unique property of this system is that -SCN can react directly with all hypohalous acids and haloamines to funnel the oxidants to HOSCN that can be selectively detoxified by the host's thioredoxin reductase but not by pathogen's thioredoxin reductases due to evolutionary divergence. New understanding of this system many allow us to develop novel approaches to simultaneously treat inflammation while preventing infections.