Alterations in transcription factor binding at the IL-2 promoter region in anergized human CD4+ T lymphocytes

Tolerogenic dendritic cells induce antigen-specific hyporesponsiveness in insulin- and glutamic acid decarboxylase 65-autoreactive T lymphocytes from type 1 diabetic patients

Tolerogenic dendritic cells (tDC) constitute a promising therapy for autoimmune diseases, since they can anergize T lymphocytes recognizing self-antigens. Patients with type 1 diabetes mellitus (T1D) have autoreactive T cells against pancreatic islet antigens (insulin, glutamic acid decarboxylase 65 -GAD65-). We aimed to determine the ability of tDC derived from T1D patients to inactivate their insulin- and GAD65-reactive T cells. CD14+ monocytes and CD4+CD45RA- effector/memory lymphocytes were isolated from 25 patients. Monocyte-derived DC were generated in the absence (control, cDC) or presence of IL-10 and TGF-β1 (tDC), and loaded with insulin or GAD65. DC were cultured with T lymphocytes (primary culture), and cell proliferation and cytokine secretion were determined. These lymphocytes were rechallenged with insulin-, GAD65- or candidin-pulsed cDC (secondary culture) to assess whether tDC rendered T cells hyporesponsive to further stimulation. In the primary cultures, tDC induced significant lower lymphocyte proliferation and IL-2 and IFN-γ secretion than cDC; in contrast, tDC induced higher IL-10 production. Lymphocytes from 60% of patients proliferated specifically against insulin or GAD65 (group 1), whereas 40% did not (group 2). Most patients from group 1 had controlled glycemia. The secondary cultures showed tolerance induction to insulin or GAD65 in 14 and 10 patients, respectively. A high percentage of these patients (70-80%) belonged to group 1. Importantly, tDC induced antigen-specific T-cell hyporesponsiveness, since the responses against unrelated antigens were unaffected. These results suggest that tDC therapy against multiple antigens might be useful in a subset of T1D patients.

Combined meta-analysis of systemic effects of allogeneic stem cell transplantation and systemic sclerosis

BACKGROUND

Chronic graft-versus-host disease (cGVHD) is a major factor of morbidity and mortality for allogeneic stem cell transplantation (aSCT). The skin and internal organ involvement is the most common systemic complication of cGVHD and closely resembles systemic sclerosis (SSc). Circulating lymphocytes characterize the autoimmune nature of both conditions. Therefore we hypothesized that the common clinical manifestation (systemic organ and skin injury) and the common underlying players (lymphocytes) justify the combined meta-analysis of these diseases.

RESULTS

The aSCT and SSc datasets were uploaded from Gene Expression Omnibus (GEO), a public functional genomics data repository. The available microarray studies of peripheral blood mononuclear cells (PBMCs) and isolated lymphocytes were limited to well established microarray platforms (Affymetrix, Agilent, Canvac, and Illumina) and experimental settings with ≥10 patients per group. The resulting pools of data were merged by unique gene identifier and analyzed by the expression genome-wide association studies (eGWAS) coupled with the subtraction of the cGVHD+ and cGVHD- molecular signatures. The eGWAS was applied to 47 and 50 lymphocyte profiles from aSCT and SSc patients, respectively. The identified 35 candidates were represented by 8 known cGVHD genes (including CXCR4, LTBR and PML) and 28 new candidate genes (including SEPX1 and DNJGB1). The further mutual subtraction of cGVHD+ and cGVHD- candidates and pathway analysis identified a list of 25 genes. Seven of these genes belong to the fibroblast development and function pathway, consisting of the well known cGVHD genes CCND1, JUN, and FOS, and the new molecular targets MMP2, FOSB, TNFAIP8, and DUSP1. These genes become primary candidates for a potential link of systemic effects of cGVHD and SSc.

CONCLUSIONS

We designed a new approach for meta-analysis by combining data from different diseases using common clinical manifestation as a linker. This allowed us to power up the insufficient standalone meta-analysis of aSCT microarray studies, by adding SSc samples to the data pool. This new method has successfully identified novel molecular targets for systemic effects of both aSCT and SSc. We believe that this approach is generalizable and can be applied to an array of diseases with common clinical manifestations.

Molecular mechanisms of T-cell anergy

Anergy is a long-term stable state of T-lymphocyte unresponsiveness to antigenic stimulation associated with the blockade of IL-2 production and proliferation. Anergy is a pathway of peripheral tolerance formation. In this review, mechanisms underlying T-cell tolerization are considered in a classical in vitro model of clonal anergy, and these mechanisms are compared with different pathways of anergy induction in vivo. Special attention is given to regulatory T-lymphocytes because, on one hand, anergy is a specific feature of these cells, and on the other hand anergy is also a mechanism of their action on target cells - effector T-lymphocytes. The role of this phenomenon in the differentiation of regulatory T-cells and also in the development of activation-induced apoptosis in effector T-lymphocytes is discussed.

SUMOylation regulates the transcriptional activity of JunB in T lymphocytes

The AP-1 family member JunB is a critical regulator of T cell function. JunB is a transcriptional activator of various cytokine genes, such as IL-2, IL-4, and IL-10; however, the post-translational modifications that regulate JunB activity in T cells are poorly characterized. We show here that JunB is conjugated with small ubiquitin-like modifier (SUMO) on lysine 237 in resting and activated primary T cells and T cell lines. Sumoylated JunB associated with the chromatin-containing insoluble fraction of cells, whereas nonsumoylated JunB was also in the soluble fraction. Blocking JunB sumoylation by mutation or use of a dominant-negative form of the SUMO-E2 Ubc-9 diminished its ability to transactivate IL-2 and IL-4 reporter genes. In contrast, nonsumoylable JunB mutants showed unimpaired activity with reporter genes controlled by either synthetic 12-O-tetradecanoylphorbol-13-acetate response elements or NF-AT/AP-1 and CD28RE sites derived from the IL-2 promoter. Ectopic expression of JunB in activated human primary CD4(+) T cells induced activation of the endogenous IL-2 promoter, whereas the nonsumoylable JunB mutant did not. Thus, our work demonstrates that sumoylation of JunB regulates its ability to induce cytokine gene transcription and likely plays a critical role in T cell activation.

FoxP3 maintains Treg unresponsiveness by selectively inhibiting the promoter DNA-binding activity of AP-1

Regulatory T cells (Tregs) have been shown to play a crucial role in maintaining self-tolerance and suppressing autoimmunity. The forkhead transcription factor, FoxP3, is a key molecule necessary and sufficient for Tregs development and function. However, the molecular mechanisms by which FoxP3 regulates the phenotypic (anergic) and the functional (suppressive) characteristics of Tregs are not well defined. Here we found that the promoter DNA-binding activity of AP-1 transcription factors is selectively inhibited in the naturally occurring CD4+ CD25+ Tregs from mice. The impaired AP-1 DNA binding is not the result of the decreased nuclear translocation of AP-1 family transcription factors, including c-Jun, JunB, and c-Fos. FoxP3 significantly suppresses both the transcriptional activity and promoter DNA-binding of AP-1 by interacting with c-Jun. The N-terminus of FoxP3, but not its C-terminus forkhead domain, specifically interacts with phosphorylated c-Jun and alters c-Jun subnuclear distribution. This N-terminus of FoxP3 with nuclear localization signals (FoxP3N/NLS) is able to suppress AP-1 transcriptional activity. Ectopic expression of FoxP3N/NLS sufficiently induces the unresponsiveness of mouse primary CD4+ CD25- T cells, whereas the full-length FoxP3 is required for the suppressive functions of Tregs. These findings uncover one of the mechanisms underlying how FoxP3 maintains the unresponsiveness of Tregs.

Functional genomics analyses of differential macaque peripheral blood mononuclear cell infections by human immunodeficiency virus-1 and simian immunodeficiency virus

The pathogenicity of the primate lentiviruses, human, and simian immunodeficiency viruses, is host-specific. Previous studies indicated that the highly pathogenic human lentivirus HIV-1 has markedly reduced pathogenicity compared to the pathogenic simian lentivirus SIV in pigtail macaques (Macaca nemestrina). We therefore hypothesized that the pigtail macaque peripheral blood mononuclear cells (mPBMCs) would respond differently to infections of HIV-1 and pathogenic SIV. To elucidate the cellular responses to the infections of HIV-1 and SIV, we infected mPBMC with these two viruses. Like infections in vivo, HIV-1 and SIV demonstrated distinct replication kinetics in mPBMCs, with HIV-1 replicating at significantly lower levels. Similarly, gene expression profiling facilitated by macaque-specific oligonucleotide microarrays also revealed distinct expression patterns of genes between the HIV-1- and SIV-infected mPBMCs; in particular, genes associated with the antigen presentation, T cell receptor, ERK/MAPK signaling, Wnt/beta-catenin signaling, and natural killer cell signaling pathways were differentially regulated between these two viruses. Most interestingly, despite the lower levels of replication, HIV-1 triggered a more robust regulation of immune response genes early after infection; the converse was true in SIV-infected mPBMCs. Our results therefore suggest that macaques may be controlling the infection of HIV-1 at an early stage through coordinated regulation of host defense pathways.

Control of interleukin-2 gene transcription: a paradigm for inducible, tissue-specific gene expression

Interleukin-2 (IL-2) is a key cytokine that controls immune cell function, in particular the adaptive arm of the immune system, through its ability to control the clonal expansion and homeostasis of peripheral T cells. IL-2 is produced almost exclusively by T cells in response to antigenic stimulation and thus provides an excellent example of a cell-specific inducible gene. The mechanisms that control IL-2 gene transcription have been studied in detail for the past 20 years and our current understanding of the nature of the inducible and tissue-specific controls will be discussed.

Expression patterns of Th1 and Th2 cytokine genes in childhood idiopathic thrombocytopenic purpura (ITP) at presentation and their modulation by intravenous immunoglobulin G (IVIg) treatment: their role in prognosis

Childhood idiopathic thrombocytopenic purpura (ITP) resolves usually after the first episode, although it may recur, and in 10% to 20% of patients develops into a chronic disorder. Evidence of the immunoregulatory role of Th1/Th2 responses in autoimmune diseases prompted us to perform a prospective study of Th1/Th2 gene expression profiles and transforming growth factor β (TGF-β) plasma levels in 18 children (median age, 6.4 years) with acute ITP, before and after intravenous immunoglobulin G (IVIg) infusion, and during a follow-up period (0.5-5 years). Initially, 12 of 18 patients had either low Th0/Th1 plus interleukin 10 (IL-10) or no in vivo cytokine gene expression (0). At 24 hours after IVIg infusion this pattern became 0 or Th2 (9 of 12) or remained low Th0/Th1 (3 of 12). During follow-up these patients did not relapse and maintained 0 or Th2 pattern without IL-10. Of the remaining 6 patients, 4 presented with a Th1 or Th0/Th1 pattern plus IL-10 that persisted after IVIg treatment (although interferon γ [IFN-γ] expression diminished) and stabilized to Th1 plus IL-10 at follow-up, which was marked by infrequent episodes of ITP. Two patients presenting with a strict Th1 pattern characterized by high expression of IFN-γ, which remained unchanged after IVIg and at follow-up, can be characterized as chronic ITP. TGF-β plasma levels were low in patients with active disease and increased in remission. Overall, acute ITP presents with Th1, Th0/Th1, or 0 in vivo cytokine gene expression. Stable remission is associated with a 0 or Th2 pattern. A 0 or Th2 pattern after IVIg gave the best prognosis, whereas sustained high expression of IFN-γ and refractoriness to IVIg were the main indicators of poor prognosis.