Menin Plays a Critical Role in the Regulation of the Antigen-Specific CD8+ T Cell Response upon Listeria Infection.

Menin, a tumor suppressor protein, is encoded by the MEN1 gene in humans. Certain germinal mutations of MEN1 induce an autosomal-dominant syndrome that is characterized by concurrent parathyroid adenomas and several other tumor types. Although menin is also expressed in hematopoietic lineages, its role in CD8+ T cells remains unclear. We generated Meninflox/flox CD4-Cre (Menin-KO) mice by crossing Meninflox/flox mice with CD4-Cre transgenic (Tg) mice to determine the role of menin in CD8+ T cells. Wild-type (WT) and Menin-KO mice were infected with Listeria monocytogenes expressing OVA to analyze the immune response of Ag-specific CD8+ T cells. Menin deficiency resulted in an impaired primary immune response by CD8+ T cells. On day 7, there were fewer Menin-KO OVA-specific CD8+ T cells compared with WT cells. Next, we adoptively transferred WT and Menin-KO OT-1 Tg CD8+ T cells into congenic recipient mice and infected them with L. monocytogenes expressing OVA to determine the CD8+ T cell-intrinsic effect. Menin-KO OT-1 Tg CD8+ T cells were outcompeted by the WT cells upon infection. Increased expression of Blimp-1 and T-bet, cell cycle inhibitors, and proapoptotic genes was observed in the Menin-KO OT-1 Tg CD8+ T cells upon infection. These data suggest that menin inhibits differentiation into terminal effectors and positively controls proliferation and survival of Ag-specific CD8+ T cells that are activated upon infection. Collectively, our study uncovered an important role for menin in the immune response of CD8+ T cells to infection.

The Transcriptional Repressor Gfi1 Plays a Critical Role in the Development of NKT1- and NKT2-Type iNKT Cells.

Gfi1 plays an important role in the development and maintenance of many hematopoietic linage cells. However, the impact of Gfi1-deficiency on the iNKT cell differentiation remains unclear. We herein demonstrate a critical role of Gfi1 in regulating the development of iNKT cell subsets. In the thymus of T cell-specific Gfi1-deficient mice, iNKT cells normally developed up to stage 2, while the number of stage 3 NK1.1pos iNKT cells was significantly reduced. Furthermore, CD4pos iNKT cells were selectively reduced in the peripheral organs of T cell-specific Gfi1-deficient mice. The α-GalCer-dependent production of IFN-γand Th2 cytokines, but not IL-17A, was severely reduced in T cell-specific Gfi1-deficient mice. In addition, a reduction of the α-GalCer-induced anti-tumor activity was observed in Gfi1-deficient mice. These findings demonstrate the important role of Gfi1 in regulating the development and function of NKT1- and NKT2-type iNKT cell subsets.

Gfi1, a transcriptional repressor, inhibits the induction of the T helper type 1 programme in activated CD4 T cells.

A transcriptional repressor Gfi1 promotes T helper type 2 (Th2) cell development and inhibits Th17 and inducible regulatory T-cell differentiation. However, the role of Gfi1 in regulating Th1 cell differentiation and the Th1-type immune response remains to be investigated. We herein demonstrate that Gfi1 inhibits the induction of the Th1 programme in activated CD4 T cells. The activated Gfi1-deficient CD4 T cells spontaneously develop into Th1 cells in an interleukin-12- and interferon-γ-independent manner. The increase of Th1-type immune responses was confirmed in vivo in Gfi1-deficient mice using a murine model of nickel allergy and delayed-type hypersensitivity (DTH). The expression levels of Th1-related transcription factors were found to increase in Gfi1-deficient activated CD4 T cells. Tbx21, Eomes and Runx2 were identified as possible direct targets of Gfi1. Gfi1 binds to the Tbx21, Eomes and Runx2 gene loci and reduces the histone H3K4 methylation levels in part by modulating Lsd1 recruitment. Together, these findings demonstrate a novel regulatory role of Gfi1 in the regulation of the Th1-type immune response.

Listeria arpJ gene modifies T helper type 2 subset differentiation.

BACKGROUND: Although the T-cell subset differentiation pathway has been characterized extensively from the view of host gene regulation, the effects of genes of the pathogen on T-cell subset differentiation during infection have yet to be elucidated. Especially, the bacterial genes that are responsible for this shift have not yet been determined. METHODS: Utilizing a single-gene-mutation Listeria panel, we investigated genes involved in the host-pathogen interaction that are required for the initiation of T-cell subset differentiation in the early phase of pathogen infection. RESULTS: We demonstrate that the induction of T helper types 1 and 2 (Th1 and Th2) subsets are separate phenomena and are mediated by distinct Listeria genes. We identified several candidate Listeria genes that appear to be involved in the host-Listeria interaction. Among them, arpJ is the strongest candidate gene for inhibiting Th2 subset induction. Furthermore, the analysis utilizing arpJ-deficient Listeria monocytogenes (Lm) revealed that the tumor necrosis factor (TNF) superfamily (Tnfsf) 9-TNF receptor superfamily (Tnfrsf) 9 interaction inhibits the Th2 response during Lm infection. CONCLUSIONS: arpJ is the candidate gene for inhibiting Th2 T-cell subset induction. The arpJ gene product influences the expression of Tnfsf/Tnfrsf on antigen-presenting cells and inhibits the Th2 T-cell subset differentiation during Listeria infection.

The Menin-Bach2 axis is critical for regulating CD4 T-cell senescence and cytokine homeostasis.

Although CD4 T-cell senescence plays an important role in immunosenescence, the mechanism behind this process remains unclear. Here we show that T cell-specific Menin deficiency results in the premature senescence of CD4 T cells, which is accompanied by the senescence-associated secretory phenotype after antigenic stimulation and dysregulated cytokine production. Menin is required for the expansion and survival of antigen-stimulated CD4 T cells in vivo and acts by targeting Bach2, which is known to regulate immune homeostasis and cytokine production. Menin binds to the Bach2 locus and controls its expression through maintenance of histone acetylation. Menin binding at the Bach2 locus and the Bach2 expression are decreased in the senescent CD4 T cells. These findings reveal a critical role of the Menin-Bach2 pathway in regulating CD4 T-cell senescence and cytokine homeostasis, thus indicating the involvement of this pathway in the inhibition of immunosenescence.

Attenuated Listeria infection activates natural killer cell cytotoxicity to regress melanoma growth in vivo.

Listeria monocytogenes infection induces various types of immune responses. The Lm-induced immunity not only protects the hosts against Lm infection but also has a therapeutic effect on other diseases such as tumors and infectious diseases. In the present study, we sought to identify the cells and molecules that are primarily responsible for the Lm-induced antitumor immune response. We investigated the mechanism of the antitumor immune response induced by Lm infection using melanoma cells and various types of gene-manipulated mice and B16F10 melanoma cells. Melanoma cells were implanted into mice intrasplenically or intraperitoneally. Lm infection of mice remarkably suppressed the growth of transplanted melanoma. The suppression of melanoma growth was due to the augmented NK cytotoxicity. The Lm-induced NK activation against melanoma was type I interferon- and signal transducer and activator of transcription (STAT)1-dependent but independent of IL-12 and IFN-gamma. In contrast to avirulent Listeria innocua and hly(-) Lm failed to induce NK activation, a mutant Lm strain with minimal hemolytic activity and with normal accessibility to cytoplasm-induced NK activation. We demonstrated that the attenuated Lm entrance into the cytoplasm induces the production of type I IFN followed by the activation of NK cells, which is essential for the Lm-induced antitumor response.

Differential effect of Listeria monocytogenes infection on cytokine production and cytotoxicity of CD8 T cells.

Bacterial infection induces a shift to type 1 CD4 T cell subset in an infected host and this shift is important for protection of the host from disease development. Many researchers think that the shift is antigen-dependent, but we previously demonstrated an initial induction step for CD4 T cell subsets during Listeria monocytogenes (Lm) infection is antigen-independent. Although Listeria is a TLR2 ligand, the immune system of the Lm-infected host responded to the pathogen to induce expression of CD69 but not CD25 on CD4 T cells, CD8 T cells and B cells even in the absence of TLR2 or MyD88. The antigen-independent activation of type 1 CD4 T cells accelerate the clearance of pathogens by activating innate immune cells with type 1 cytokines. Type 1 CD4 T cells and CD8 T cells also collaborate to protect the host from intracellular Lm infection. Since CD8 T cells function mainly as cytotoxic T cells and CD69-positive CD8 T cells increase during Lm-infection, cytotoxic activity of CD8 T cells was evaluated during Lm-infection. Although CD8 T cells were activated to produce IFN-gamma, the cytotoxic function of CD8 T cells in Lymphocytic choriomeningitis virus (LCMV) p14 TCR-transgenic mouse was not augmented by Lm-infection. Therefore, Lm-infection differentially influences on cytokine production and cytotoxicity of CD8 T cells.