Table 1.
Defensive functions of the stratum corneum
| Function | Localization | Structural basis | Biochemical basis | Abnormal in atopic dermatitis |
|---|---|---|---|---|
| Permeability barrier + xenobiote penetration |
Extracellular matrix | Lamellar bilayers | Cer:Chol:FFA (1:1 :1) | Yes |
| Antimicrobial defense | Extracellular matrix | Lamellar bilayers | LL-37, hBD2 | Yes |
| ? Corneocyte cytosol | ? | ?RNase7, psoriasin | No | |
| Cohesion/desquamation | Extracellular matrix | Corneodesmosomes | Protease/antiprotease; cholesterol sulfate | Yes |
| Mechanical/rigidity | Corneocyte | Cornified envelope | Isopeptide (γ-glutamyl x-linking), Ca++ | ? |
| Hydration | Corneocyte | Corneocyte lipid envelope | ω-OH-ceramides | Yes |
| Extracellular matrix | Sebaceous glands | TG → Glycerol | ? | |
| Basal keratinocye | Plasma membrane | AQP3 channel | ? | |
| UV defense | Corneocyte cytosol | – | FLG → UCA | ? |
| Antioxidant defense | Skin surface | Sebaceous glands | Vitamin E, CoQ | Yes |
| Extracellular matrix | ? |
?, not known; AQP, aquaporin; Cer, ceramides; chol, cholesterol; CoQ, coenzyme Q; FFAs, free fatty acids; FLG, filaggrin; hBD2, human-β-defensin 2; LL-37, cathelicidin; UCA, urocanic acid; UV, ultraviolet.