TSLP-tickled mast cells

If you suffer a skin allergy, don't be so quick to blame your T cells; they might not be behind it. Allakhverdi and colleagues now show on page 253 that mast cells, activated by a cytokine from epithelial cells, can jump- start T cell–independent inflammation.

Skin and epithelial cells irritated by allergens or by injury produce a cytokine called thymic stromal lymphopoietin (TSLP). This cytokine masterminds a sequence of dendritic cell (DC)–mediated reactions that attract T helper (Th)-2 cells to the hot zone.

In addition to Th2 cells, however, other cells such as mast cells also arrive on the scene. Mast cell recruitment and activation was thought to be dependent on signals from Th2 cells. But, as Allakhverdi et al. now show, mast cells themselves bear TSLP receptors and get directly activated when...