Human skin engages different epidermal layers to provide distinct innate defense mechanisms

Keratinocytes are able to sense bacteria or bacterial products leading to a rapid defense reaction by the increased expression of antimicrobial peptides and cytokines. Recent data by Percoco and collaborators published in Experimental Dermatology indicate that bacteria colonizing the skin surface induce a differential spatial expression pattern of antimicrobial peptides and cytokines. Using laser capture microdissection followed by real-time PCR as well as immunohistochemistry and transmission electron microscopy, the authors provide evidence that antimicrobial peptides such as human beta-defensin (hBD)-2 and -3 were more strongly induced in the uppermost epidermal layers, whereas the main induction of cytokines such as IL-1beta and IL-6 occurred in the lower parts of the epidermis.