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. Enforced expression of BCL6 in EGR2/3-deficient CD4 T cells partially restored Tfh differentiation and GC formation in response to virus infection. Our findings demonstrate a novel function of EGR2/3 that is important for Tfh cell development and Tfh cell-mediated B cell immune responses.

Early growth response gene-2 controls IL-17 expression and Th17 differentiation by negatively regulating Batf.

Early growth response gene (Egr)-2 is important for the maintenance of T cell homeostasis and controls the development of autoimmune disease. However, the underlying mechanisms are unknown. We have now discovered that Egr-2, which is induced by TGF-ß and IL-6, negatively regulates the expression of IL-17, but not IL-2 or IFN-γ, in effector T cells. In the absence of Egr-2, CD4 T cells produce high levels of Th17 cytokines, which renders mice susceptible to experimental autoimmune encephalomyelitis induction. T cells lacking Egr-2 show increased propensity for Th17, but not Th1 or Th2, differentiation. Control of IL-17 expression and Th17 differentiation by Egr-2 is due to inhibition of Batf, a transcription factor that regulates IL-17 expression and Th17 differentiation. Egr-2 interacts with Batf in CD4 T cells and suppresses its interaction with DNA sequences derived from the IL-17 promoter, whereas the activation of STAT3 and expression of retinoic acid-related orphan receptor γt are unchanged in Th17 cells in the absence of Egr-2. Thus, Egr-2 plays an important role to intrinsically control Th17 differentiation. We also found that CD4 T cells from multiple sclerosis patients have reduced expression of Egr-2 and increased expression of IL-17 following stimulation with anti-CD3 in vitro. Collectively, our results demonstrate that Egr-2 is an intrinsic regulator that controls Th17 differentiation by inhibiting Batf activation, which may be important for the control of multiple sclerosis development.

The transcription factors Egr2 and Egr3 are essential for the control of inflammation and antigen-induced proliferation of B and T cells.

Lymphocytes provide optimal responses against pathogens with minimal inflammatory pathology. However, the intrinsic mechanisms regulating these responses are unknown. Here, we report that deletion of both transcription factors Egr2 and Egr3 in lymphocytes resulted in a lethal autoimmune syndrome with excessive serum proinflammatory cytokines but also impaired antigen receptor-induced proliferation of B and T cells. Egr2- and Egr3-defective B and T cells had hyperactive signal transducer and activator of transcription-1 (STAT1) and STAT3 while antigen receptor-induced activation of transcription factor AP-1 was severely impaired. We discovered that Egr2 and/or Egr3 directly induced expression of suppressor of cytokine signaling-1 (SOCS1) and SOCS3, inhibitors of STAT1 and STAT3, and also blocked the function of Batf, an AP-1 inhibitor, in B and T cells. Thus, Egr2 and Egr3 regulate B and T cell function in adaptive immune responses and homeostasis by promoting antigen receptor signaling and controlling inflammation.