Atopic dermatitis is a common allergic skin disorder that often precedes the development of allergy in distal tissues such as the lung. In Mucosal Immunology, Ziegler and colleagues describe how the epithelial cell–associated cytokine TSLP can drive this so-called 'atopic march' from one tissue to another. Intradermal injection of mice with TSLP plus antigen results in asthma after subsequent lung challenge with that same antigen alone. TSLP expression in the lung is not required for the manifestation of asthma, but an antigen-specific memory CD4+ T cell response is essential for this. Similar results are obtained after inducible expression of TSLP by keratinocytes. IL-25 is another epithelial cell–derived cytokine linked to allergy; however, it has no role in the dissemination of allergy from the skin to the lungs. Although mice can be made tolerant to asthma orally, this is possible only if done before skin sensitization, a finding with implications for the translation of such immunotherapy to patients.

Mucosal Immunol. 5, 342–351 (2012)