Differential expression and in vivo secretion of the antimicrobial peptides psoriasin (S100A7), RNase 7, human beta-defensin-2 and -3 in healthy human skin.

Antimicrobial peptides (AMP) are key players in the skin's defense system. Previous observations suggest a site- and age-dependent expression of individual AMP. We investigated the expression and secretion patterns of four important AMP in a representative collective of healthy human skin samples. Levels of psoriasin, RNase 7 and hBD-3 expression - assessed by immunohistochemistry - varied between different body localisations. Older individuals expressed hBD-2 more frequently. No gender-related expression was observed. The in vivo secretion of psoriasin, measured in skin washing fluids using ELISA, was related to body localisation and age, whereas RNase 7 secretion showed no significant differences regarding these variables. HBD-2 and -3 secretion could not be detected. Our findings suggest the usage of control samples matching localisation and approximate age (in the case of hBD-2) for comparative immunohistochemical analysis. To avoid bias through great interindividual differences, sufficient large collectives should be used for in vivo secretion analyses.