Antigen stimulation leads to TSLP (thymic stromal lymphopoietin) or IL(interleukin)-25 production from stromal cells, which subsequently stimulates type 2 effector cytokine expression from various cell types, including innate lymphoid cells, basophils and mast cells. Alternatively, IL-33, which induces many of the features similar to IL-25 and TSLP, is released as an active form from necrotic cells and acts as an alarmin. Besides IL-33, uric acid is released from dying cells and produced by macrophages after alum or house dust mite stimulation. In addition, certain antigens such as Omega-1 from the helminth S. mansoni prime dendritic cells, so that they guide CD4+ T cells towards a Th(T helper cells)2 response. Abbreviations: DC, dendritic cell; HDM, house dust mite; IL, interleukin; Th, T helper cell; TSLP, thymic stromal lymphopoietin.