TSLP Expression: Analysis with a ZsGreen TSLP Reporter Mouse

Thymic stromal lymphopoietin (TSLP) is a type I cytokine that plays a central role in induction of allergic inflammatory responses. Its principal targets have been reported to be dendritic cells and / or CD4 T cells; epithelial cells are a principal source. We report here the development of a reporter mouse (TSLP-ZsG) in which a ZsGreen (ZsG)-encoding construct has been inserted by recombineering into a bacterial artificial chromosome (BAC) immediately at the translation initiating ATG of TSLP. The expression of ZsG by mice transgenic for the recombinant BAC appears to be a faithful surrogate for TSLP expression, particularly in keratinocytes and medullary thymic epithelials cells (mTECs). A comparison of gene expression in ZsG expressing and ZsG negative mTECs and cortical thymic epithelial cells, which are all ZsG negative, revealed that all three populations can be distinguished from one another. In particular ZsG (and TSLP) expressing mTECs and ZsG- mTECs are separable populations based on gene expression profiling. Little or no expression of ZsG is observed in bone marrow-derived mast cells or basophils or in CD45+ cells infiltrating TSLP/ZsG-expressing skin. Using the TSLP-ZsG reporter mouse, we show that TNFa and IL-4/IL-13 are potent inducers of TSLP expression by keratinocytes and that local activation of Th2 and Th1 cells induces keratinocyte TSLP expression. We suggest that the capacity of TSLP to both induce Th2 differentiation and to be induced by activated Th2 cells raises the possibility that TSLP may be involved in a positive feedback loop to enhance allergic inflammatory conditions. comparison of reporter mouse construct types ZsG-cTEC, ZsG-mTEC and ZsG+