Programming of a pathogenic Th2 state by TSLP signaling in CD4+ T cells. Mus musculus

Pathogenesis of allergic diseases including asthma is strongly associated with robust responses of allergen-specific Th2 cells, which produce high levels of IL-4, IL-5, IL-9, and IL-13. Despite evidence for pathogenic Th2 cells in the induction and propagation of allergic disorders, signals required for differentiation of such cells remain largely unknown. Thymic stromal lymphopoietin (TSLP) is a cytokine that is expressed upon epithelial injury, dysfunction or infection and is strongly implicated in the pathogenesis of atopic dermatitis (AD) and asthma. Although indirect regulation of Th2 differentiation via TSLP-stimulated dendritic cells well known, direct effects of TSLP on Th2 differentiation in vivo have not been rigorously analyzed. We show that TSLP may initiate Th2 response independent on IL-4 signal and increases sensitivity of CD4 cells to IL-4 stimulation inducing more robust expression of IL-4, IL-5, and IL-13 by human and mouse CD4 cells. This more potent effector state appears to be stably programmed in memory Th2 cells. As part of molecular mechanism, we demonstrate that TSLP and IL-4 signals induce distinctive genome wide alterations in activating histone modification (H3K27Ac, H3K36Me3, and H3K4Me3). We propose that TSLP acts in coordination with IL-4 to generate a more potent Th2 state that could underlie persistence and propagation of allergic disorders. Overall design: Mouse CD4 cells activated with TCR signal in the presence or absence of TSLP or IL-4 for different time points in vitro.