Pulling the epithelial trigger

Epithelial cells surround the sites of allergen entry into the body, but whether these cells play a role in triggering the pathologic immune cascade in diseases such as atopic dermatitis has remained unclear. In 10 June Advanced Online Nature Immunology, Vassili Soumelis and colleagues from DNAX, Palo Alto, California, show that human epithelial cells can trigger dendritic cell–mediated allergic inflammation by producing thymic stromal lymphopoietin (TSLP).

Soumelis et al. compared the effects of TSLP, IL-7, CD40 ligand (CD40L) and lipopolysaccharide (LPS) on human CD11c+ (DC) activation. They observed that TSLP could activate DCs and induce production of the TH2-attracting chemokines TARC (thymus and activation-regulated chemokine) and MDC (macrophage-derived chemokine). TSLP-activated DCs primed naïve TH cells to produce proallergic cytokines (Nat Immunol 2002, DOI:10.1038/ni805).

In addition, they found that epithelial cells — especially keratinocytes from patients with atopic dermatitis —express high levels of TSLP, which is associated...