STAT5-Induced Lunatic Fringe during Th2 Development Alters Delta-like 4–Mediated Th2 Cytokine Production in Respiratory Syncytial Virus–Exacerbated Airway Allergic Disease

Notch activation plays an important role in T cell development and mature T cell differentiation. In this study, we investigated the role of Notch activation in a mouse model of respiratory syncytial virus (RSV)–exacerbated allergic airway disease. During RSV exacerbation, in vivo neutralization of a specific Notch ligand, Delta-like ligand (Dll)-4, significantly decreased airway hyperreactivity, mucus production, and Th2 cytokines. Lunatic Fringe (Lfng), a glycosyltransferase that enhances Notch activation by Dll4, was increased during RSV exacerbation. Lfng loss of function in Th2-skewed cells inhibited Dll4-Notch activation and subsequent IL-4 production. Further knockdown of Lfng in T cells in CD4Cre + Lfng fl/fl mice showed reduced Th2 response and disease pathology during RSV exacerbation. Finally, we identified STAT5-binding cis -acting regulatory element activation as a critical driver of Lfng transcriptional activation. These data demonstrate that STAT5-dependent amplification of Notch-modifying Lfng augments Th2 response via Dll4 and is critical for amplifying viral exacerbation during allergic airway disease.