Psoriasin (S100A7) is a principal antimicrobial peptide of the human tongue.

The human tongue is particularly resistant to bacterial infections although the mouth is continuously exposed to a complex and abundant ensemble of microbes, such as the common intestinal bacterium Escherichia coli. We show that lingual epithelia produce and release, as a primary E. coli-killing compound, the S100 protein psoriasin. No significant reduction in psoriasin release could be achieved through repeated rinsing of the epithelial surface of the tongue. Psoriasin is produced in the upper layers of the lingual epithelia but is lacking in the most superficial and basal cells. It displays a gradient pattern of expression with decreasing expression from the anterior one-third to the posterior portion of the tongue. Thus, psoriasin may be the key to the resistance of the human tongue toward E. coli.