The transcriptional repressor BTB and CNC homology 2 (Bach2) is thought to be mainly expressed in B cells with specific functions such as class switch recombination and somatic hypermutation, but its function in T cells is not known. We found equal Bach2 expression in T cells and analyzed its function using Bach2-deficient (−/−) mice. Although T-cell development was normal, numbers of peripheral naive T cells were decreased, which rapidly produced Th2 cytokines after TCR stimulation. Bach2 −/− naive T cells highly expressed genes related to effector-memory T cells such as CCR4, ST-2 and Blimp-1. Enhanced expression of these genes induced Bach2 −/− naive T cells to migrate toward CCR4-ligand and respond to IL33. Forced expression of Bach2 restored the expression of these genes. Using Chromatin Immunoprecipitation (ChIP)-seq analysis, we identified S100 calcium binding protein a, Heme oxigenase 1, and prolyl hydroxylase 3 as Bach2 direct target genes, which are highly expressed in effector-memory T cells. These findings indicate that Bach2 suppresses effector memory-related genes to maintain the naive T-cell state and regulates generation of effector-memory T cells. Kruppel-like factor 2 (KLF2) is one of those TF, which regulates the expression of the sphingosine-1-phosphate receptor-1 (S1pr1) in SP cells (2). S1pr1 is required for the egress of SP cells from the thymus, and thus KLF2-deficient (−/−) SP cells accumulate in the thymus. KLF2 positively regulates S1pr1 expression through direct binding to its promoter. KLF2 −/− mice also develop an unusual population of innate-like CD8 +

Background: Systemic lupus erythematosus (SLE) is characterised by dysregulation of autoreactive lymphocytes and antigen-presenting cells. Signalling through Toll-like receptor 9 (TLR9), a mediator of innate immune responses, has a role in activation of dendritic cells and autoreactive B cells. Objective: To investigate whether TLR9 polymorphisms are associated with an increased risk of SLE. Methods: DNA samples were obtained from 220 Japanese patients with SLE (with .4 American College of Rheumatology criteria for SLE) and 203 controls. The genetic variations of TLR9 were detected by PCR, followed by DNA sequencing. The promoter and enhancer activities of TLR9 were measured by luciferase reporter gene assay. The titres of anti-dsDNA antibodies in sera from control or TLR9-deficient mice were analysed by ELISA. Results: The G allele at position +1174 (located in intron 1 of TLR9) is closely associated with an increased risk of SLE (p = 0.029). Furthermore, patients with SLE tend to have C allele at position 21486 (p = 0.11). Both alleles down regulate TLR9 expression by reporter gene assay. TLR9-deficient mice under a C57BL/6 background possess higher titres of anti-dsDNA serum antibodies than control C57BL/6 mice. Conclusions: These results indicate that the presence of the G allele at position +1174 of TLR9 predisposes humans to an increased risk of SLE. It is speculated that TLR9 normally prevents the development of human SLE.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known to suppress T cell-dependent immune reactions through the activation of the arylhydrocarbon receptor (AhR).Our previous findings suggest that TCDD inhibits the activation and subsequent expansion of T cells following antigen stimulation in mice, leading to a decreased level of T cell-derived cytokines involved in antibody production. In the present study, we investigated the effects of activated AhR on T cells by transiently expressing a constitutively active AhR (CA-AhR) mutant in AhR-null Jurkat T cells. In agreement with our previous findings, CA-AhR markedly inhibited the growth of Jurkat T cells. The inhibited cell growth was found to be concomitant with both an increase in the annexin V-positive apoptotic cells and the accumulation of cells in the G 1 phase. The growth inhibition was also shown to be mediated by both xenobiotic response element (XRE)-dependent and -independent mechanisms, because an A78D mutant of the CA-AhR, which lacks the ability of XRE-dependent transcription, partially inhibited the growth of Jurkat T cells. Furthermore, we demonstrated that CA-AhR induces expression changes in genes related to apoptosis and cell cycle arrest. These expression changes were shown to be solely mediated in an XREdependent manner, because the A78D mutant of the CAAhR did not induce them. To summarize, these results suggest that AhR activation causes apoptosis and cell cycle arrest, especially through expression changes in genes related to apoptosis and cell cycle arrest by the XRE-dependent mechanism, leading to the inhibition of T cell growth.

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by scattered fibrotic lesions in the lungs. The pathogenesis and genetic basis of IPF remain poorly understood. Here, we show that a homozygous missense mutation in SFTPA1 caused IPF in a consanguineous Japanese family. The mutation in SFTPA1 disturbed the secretion of SFTPA1 protein. Sftpa1 knock-in (Sftpa1-KI) mice that harbored the same mutation as patients spontaneously developed pulmonary fibrosis that was accelerated by influenza virus infection. Sftpa1-KI mice showed increased necroptosis of alveolar epithelial type II (AEII) cells with phosphorylation of IRE1α leading to JNK-mediated up-regulation of Ripk3. The inhibition of JNK ameliorated pulmonary fibrosis in Sftpa1-KI mice, and overexpression of Ripk3 in Sftpa1-KI mice treated with a JNK inhibitor worsened pulmonary fibrosis. These findings provide new insight into the mechanisms of IPF in which a mutation in SFTPA1 promotes necroptosis of AEII cells through JNK-mediated up-regulation of Ripk3, highlighting the necroptosis pathway as a therapeutic target for IPF.

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Intestinal intraepithelial lymphocytes (IELs) expressing CD8αα on αβ T cells (TCRαβ + CD8αα + IELs) have suppressive capabilities in enterocolitis, but the mechanism that maintains homeostasis and cell number is not fully understood. Here, we demonstrated that the number of TCRαβ + CD8αα + IELs was severely reduced in mice lacking recombination signal binding protein for immunoglobulin kappa J region ( Rbpj ) or Notch1 and Notch2 in T cells. Rbpj -deficient TCRαβ + CD8αα + IELs expressed low levels of Atp8a2 , which encodes a protein with flippase activity that regulates phospholipid asymmetry of plasma membrane such as flipping phosphatidylserine in the inner leaflet of plasma membrane. Rbpj -deficient TCRαβ + CD8αα + IELs cannot maintain phosphatidylserine in the inner leaflet of the plasma membrane. Furthermore, depletion of intestinal macrophages restored TCRαβ + CD8αα + IELs in Rbpj -deficient mice, suggesting that exposure of phosphatidylserine on the plasma membrane in Rbpj -deficient TCRαβ + CD8αα + IELs acts as an “eat-me” signal. Together, these results revealed that Notch–Atp8a2 is a fundamental regulator for IELs and highlighted that membrane phospholipid asymmetry controlled by Notch-mediated flippase expression is a critical determinant in setting or balancing the number of TCRαβ + CD8αα + IELs.