STAT4 Directs a Protective Innate Lymphoid Cell Response to Gastrointestinal Infection.

Innate lymphoid cells (ILCs) are strategically positioned at mucosal barrier surfaces where they respond quickly to infection or injury. Therefore, we hypothesized that ILCs are key contributors to the early immune response in the intestine against Listeria monocytogenes Using a modified strain of L. monocytogenes that mimics human gastrointestinal listeriosis in mice, we find ILCs to be essential for control of early replication of L. monocytogenes in the intestine as well as for restricted dissemination of bacteria to peripheral tissues. Specifically, group 1 ILCs (ILC1s) and group 3 ILCs (ILC3s) respond to infection with proliferation and IFN-γ and IL-22 production. Mechanistically, we show that the transcription factor STAT4 is required for the proliferative and IFN-γ effector response by ILC1s and ILC3s, and loss of STAT4 signaling in the innate immune compartment results in an inability to control bacterial growth and dissemination. Interestingly, STAT4 acts acutely as a transcription factor to promote IFN-γ production. Together, these data illustrate a critical role for ILCs in the early responses to gastrointestinal infection with L. monocytogenes and identify STAT4 as a central modulator of ILC-mediated protection.