Table 2.

Shared structural and biochemical features of permeability and antimicrobial barriers

Feature	Permeability barrier	Antimicrobial barrier
Cohesive stratum corneum	+	+
Replete lamellar matrix	+	+
Low H2O content of stratum corneum	+	+
Acidic pH of stratum corneum	+	+
Stratum corneum extracellular lipids     (e.g. FFAs)	+	+
Secreted epidermal AMP (e.g. LL-37)	+	+
Secreted protease inhibitors	+	+
Normal microbial flora	?	+

FFAs, free fatty acids; LL-37, cathelicidin.