In this study we will focus on the early stages of the immune response to establish how allergens interact with immune and non-immune cells to direct the initiation of allergic immune responses and immune pathology. We will focus on epithelial cells, the first line of exposure to allergens, and on dendritic cells, the immune cells that initiate T-cell immune responses. We will investigate the timing and site of production of a recently redefined cytokine, thymic stromal lymphopoietin (TSLP), produced by epithelial cells exposed to allergens and parasite infections. We will ask whether TSLP is the key factor that instructs dendritic cells to initiate allergic immune responses, and investigate its role in immune memory. Results from this study will establish whether TSLP is a suitable target for allergic conditions including asthma, food allergy and atopic dermatitis, and generate a platform for identifying the environmental and functional signatures associated with allergens of humans.