Cutting Edge: Immunity and IFN-γ Production during Listeria monocytogenes Infection in the Absence of T-bet

Abstract
The T-box transcription factor T-bet is an important regulator of IFN-γ production in all cell types and is considered to be essential for the generation of CD4 Th1 T cells. IFN-γ in turn plays a critical role in immunity to many infectious agents. In this study, we demonstrate that T-bet is not required for host resistance to primary Listeria monocytogenes (LM) infection. In the innate immune phase, control of LM replication, serum IFN-γ, and numbers of IFN-γ-producing NK cells were similar in T-bet-deficient and control mice. In the adaptive immune phase, there was no defect in bacterial clearance or in the numbers of LM-specific IFN-γ-producing CD8 T cells in T-bet-deficient mice and only a modest, although significant, reduction in the numbers of Th1 CD4 T cells and IFN-γ secretion by CD4 T cells. Thus, host resistance and the generation of IFN-γ-producing cells in response to LM infection are not substantially compromised in the absence of T-bet.