Transcription factors early growth response gene (Egr) 2 and 3 control inflammatory responses of tolerant T cells.

Introduction: Impaired proliferation and production of IL2 are the hallmarks of experimental T cell tolerance. However, in most autoimmune diseases, auto-reactive T cells do not display hyper proliferation, but inflammatory phenotypes.

Methods: We have now demonstrated that the transcription factors Egr2 and 3 are important for the control of inflammatory cytokine production by tolerant T cells, but not for tolerance induction.

Egr2 and 3 control adaptive immune responses by temporally uncoupling expansion from T cell differentiation.

Egr2 and 3 are important for maintaining immune homeostasis. Here we define a fundamental function of Egr2 and 3 operating as a checkpoint that controls the transition between clonal expansion and differentiation of effector T cells. Egr2 and 3 deficiency resulted in defective clonal expansion but hyperactivation and excessive differentiation of T cells in response to viral infection.

Egr2 and 3 Inhibit T-bet-Mediated IFN-γ Production in T Cells.

T-bet is important for differentiation of cytotoxic CD8 and Th1 CD4 T cells. We have discovered that Egr2 and 3 are potent inhibitors of T-bet function in CD4 and CD8 effector T cells. Egr2 and 3 were essential to suppress Th1 differentiation in Th2 and Th17 conditions in vitro and also to control IFN-γ-producing CD4 and CD8 T cells in response to virus infection.

Early Growth Response Genes 2 and 3 Regulate the Expression of Bcl6 and Differentiation of T Follicular Helper Cells.

T follicular helper (Tfh) cells support differentiation of B cells to plasma cells and high affinity antibody production in germinal centers (GCs), and Tfh differentiation requires the function of B cell lymphoma 6 (BCL6). We have now discovered that early growth response gene 2 (EGR2) and EGR3 directly regulate the expression of Bcl6 in Tfh cells, which is required for their function in regulation of GC formation. In the absence of EGR2 and -3, the expression of BCL6 in Tfh cells is defective, leading to impaired differentiation of Tfh cells, resulting in a failure to form GCs following virus infection and defects in production of antiviral antibodies.