Severely Impaired Clonal Deletion of CD4+T Cells in Low-Dose Irradiated Mice: Role of T Cell Antigen Receptor and IL-7 Receptor Signals

Lymphopenia at diagnosis of ANCA-vasculitis with renal involvement is correlated with severity and renal prognosis

BACKGROUND

Lymphopenia is commonly observed in autoimmune diseases, where it has been associated with disease activity or prognosis. However, in ANCA-associated vasculitis (AAV) only few, small-scale studies have been targeted to this issue. Research has not yet focused on AAV with renal involvement (AAV-RI) patients. Thus, the aim of this study was to analyze the association between lymphocyte counts and outcomes in a large cohort of AAV-RI patients.

METHODS

We used the Maine-Anjou AAV registry that retrospectively gathers data on consecutive patients affected by AAV in four French Nephrology Centers, recorded since January 2000. We analyzed clinical, biological, and histological data at diagnosis of AAV-RI. Risk factors for end-stage kidney disease (ESKD) were analyzed. Event-free survival was also assessed.

RESULTS

Among the 145 patients included in the study, those with lymphopenia at diagnosis had a lower renal function at baseline (eGFR 13 mL/min vs 26 mL/min, p = 0.002) and were more likely to require kidney replacement therapy (51% vs 25%, p = 0.003). Lymphopenia was correlated with histological lesions and especially with the percentage of sclerotic glomeruli (p = 0.0027). ESKD-free survival was lower in lymphopenic patients (p < 0.0001). In multivariate Cox analysis, lymphopenia was an independent risk factor for ESKD (HR 4.47 (95% confidence interval: [2.06-9.72], p < 0.001).

CONCLUSION

Lymphopenia correlates with the severity of AAV glomerulonephritis at diagnosis and predicts poor renal outcome. In this view, lymphopenia could be used as a simple and cost-effective biomarker to assess renal prognosis at AAV-RI diagnosis.

Interferon-γ Receptor Signaling in Dendritic Cells Restrains Spontaneous Proliferation of CD4+ T Cells in Chronic Lymphopenic Mice

In lymphopenic mice, T cells become activated and undergo lymphopenia-induced proliferation (LIP). However, not all T cells are equally sensitive to lymphopenia. Several lymphopenia-insensitive T cell clones were described and their non-responsiveness was mainly attributed to clone-specific properties. Here, we provide evidence for an additional, host-dependent mechanism restraining LIP of lymphopenia-insensitive CD4+ T cells. We show that such cells undergo LIP in lymphopenic mice lacking IFN-γ receptor (IFN-γR) expression, a process, which is promoted by the autocrine action of T cell-derived IFN-γ. Additionally, LIP of lymphopenia-insensitive CD4+ T cells requires an intact microflora and is accompanied by the massive accumulation of IL-6 and dendritic cells (DCs). Consistent with these results, IL-6 neutralization and the DC-specific restoration of IFN-γR expression are both sufficient to restrict LIP. Hence, the insensitivity of CD4+ T cells to lymphopenia relies on cell-intrinsic properties and a complex interplay between the commensal microflora, IL-6, IFN-γR+ DCs, and T cell-derived IFN-γ.

Groth B. Tumour-specific CD4 T cells eradicate melanoma via indirect recognition of tumour-derived antigen

The importance of CD4 T cells in tumour immunity has been increasingly recognised, with recent reports describing robust CD4 T cell-dependent tumour control in mice whose immune-regulatory mechanisms have been disturbed by irradiation, chemotherapy, immunomodulatory therapy and/or constitutive immunodeficiency. Tumour control in such models has been attributed in large part to direct Major Histocompatibility Complex (MHC) class II-dependent CD4 T cell killing of tumour cells. To test whether CD4 T cells can eradicate tumours without directly killing tumour cells, we developed an animal model in which tumour-derived antigen could be presented to T-cell receptor (TCR)-transgenic CD4 T cells by host but not tumour MHC class II molecules. In I-E(+) mice bearing I-E(null) tumours, naive I-E-restricted CD4 T cells proliferated locally in tumour-draining lymph nodes after recognising tumour-derived antigen on migratory dendritic cells. In lymphopaenic but not immunosufficient hosts, CD4 T cells differentiated into polarised T helper type 1 (Th1) cells expressing interferon gamma (IFNγ), tumor necrosis factor alpha (TNFα) and interleukin (IL)-2 but little IL-17, and cleared established tumours. Tumour clearance was enhanced by higher TCR affinity for tumour antigen-MHC class II and was critically dependent on IFNγ, as demonstrated by early tumour escape in animals treated with an IFNγ blocking antibody. Thus, CD4 T cells and IFNγ can control tumour growth without direct T-cell killing of tumour cells, and without requiring additional adaptive immune cells such as CD8 T cells and B cells. Our results support a role for effective CD4 T cell-dependent tumour immunity against MHC class II-negative tumours.

Ionizing Radiation Impairs T Cell Activation by Affecting Metabolic Reprogramming

Ionizing radiation has a variety of acute and long-lasting adverse effects on the immune system. Whereas measureable effects of radiation on immune cell cytotoxicity and population change have been well studied in human and animal models, little is known about the functional alterations of the surviving immune cells after ionizing radiation. The objective of this study was to delineate the effects of radiation on T cell function by studying the alterations of T cell receptor activation and metabolic changes in activated T cells isolated from previously irradiated animals. Using a global metabolomics profiling approach, for the first time we demonstrate that ionizing radiation impairs metabolic reprogramming of T cell activation, which leads to substantial decreases in the efficiency of key metabolic processes required for activation, such as glucose uptake, glycolysis, and energy metabolism. In-depth understanding of how radiation impacts T cell function highlighting modulation of metabolism during activation is not only a novel approach to investigate the pivotal processes in the shift of T cell homeostasis after radiation, it also may lead to new targets for therapeutic manipulation in the combination of radiotherapy and immune therapy. Given that appreciable effects were observed with as low as 10 cGy, our results also have implications for low dose environmental exposures.

Stable activity of diabetogenic cells with age in NOD mice: dynamics of reconstitution and adoptive diabetes transfer in immunocompromised mice

The non-obese diabetic (NOD) mouse is a prevalent disease model of type 1 diabetes. Immune aberrations that cause and propagate autoimmune insulitis in these mice are being continually debated, with evidence supporting both dominance of effector cells and insufficiency of suppressor mechanisms. In this study we assessed the behaviour of NOD lymphocytes under extreme expansion conditions using adoptive transfer into immunocompromised NOD.SCID (severe combined immunodeficiency) mice. CD4(+)  CD25(+) T cells do not cause islet inflammation, whereas splenocytes and CD4(+)  CD25(-) T cells induce pancreatic inflammation and hyperglycaemia in 80-100% of the NOD.SCID recipients. Adoptively transferred effector T cells migrate to the lymphoid organs and pancreas, proliferate, are activated in the target organ in situ and initiate inflammatory insulitis. Reconstitution of all components of the CD4(+) subset emphasizes the plastic capacity of different cell types to adopt effector and suppressor phenotypes. Furthermore, similar immune profiles of diabetic and euglycaemic NOD.SCID recipients demonstrate dissociation between fractional expression of CD25 and FoxP3 and the severity of insulitis. There were no evident and consistent differences in diabetogenic activity and immune reconstituting activity of T cells from pre-diabetic (11 weeks) and new onset diabetic NOD females. Similarities in immune phenotypes and variable distribution of effector and suppressor subsets in various stages of inflammation commend caution in interpretation of quantitative and qualitative aberrations as markers of disease severity in adoptive transfer experiments.

Regulatory T-cell abnormalities and the global epidemic of immuno-inflammatory disease

The incidence of autoimmune, allergic and inflammatory disease is increasing due to as yet unidentified environmental factors related to western living conditions. Here, I propose that alterations in the gut microbiome, acting via regulatory T cells (Tregs), may be responsible for this epidemic. Tregs control the threshold for peripheral antigen recognition via tonic downregulation of dendritic cell (DC) costimulation, and are also implicated in maintaining the tolerogenic function of DCs. In this model, minor perturbations in Treg number or function are predicted to lower the activation threshold, allowing proliferation and differentiation of self-reactive CD4T cells of too low an affinity to have undergone negative selection in the thymus. Failure to maintain the tolerogenic commitment of DCs exposed to commensal microbes and allergens could result in potentially pathogenic, allergic and inflammatory responses at epithelial surfaces.

Langerhans cells are precommitted to immune tolerance induction

Antigen-dependent interactions between T lymphocytes and dendritic cells (DCs) can produce two distinct outcomes: tolerance and immunity. It is generally considered that all DC subsets are capable of supporting both tolerogenic and immunogenic responses, depending on their exposure to activating signals. Here, we tested whether epidermal Langerhans cells (LCs) can support immunogenic responses in vivo in the absence of antigen presentation by other DC subsets. CD4 T cells responding to antigen presentation by activated LCs initially proliferated but then failed to differentiate into effector/memory cells or to survive long term. The tolerogenic function of LCs was maintained after exposure to potent adjuvants and occurred despite up-regulation of the costimulatory molecules CD80, CD86, and IL-12, but was consistent with their failure to translocate the NF-κB family member RelB from the cytoplasm to the nucleus. Commitment of LCs to tolerogenic function may explain why commensal microorganisms expressing Toll-like receptor (TLR) ligands but confined to the skin epithelium are tolerated, whereas invading pathogens that breach the epithelial basement membrane and activate dermal DCs stimulate a strong immune response.

Autoimmunity in common variable immunodeficiency: correlation with lymphocyte phenotype in the French DEFI study

Common variable immunodeficiency (CVID) is the most frequent clinically expressed primary immunodeficiency in adults and is characterized by primary defective immunoglobulin production. Besides recurrent infectious manifestations, up to 20% of CVID patients develop autoimmune complications. In this study, we took advantages of the French DEFI database to investigate possible correlations between peripheral lymphocyte subpopulations and autoimmune clinical expression in CVID adult patients. In order to analyse homogeneous populations of patients with precise clinical phenotypes, we first focused on patients with autoimmune cytopenia because they represent prototypic autoantibody mediated diseases. In a secondary analysis, we have tested our conclusions including all "autoimmune" CVID patients. We describe one of the largest European studies with 311 CVID patients, including 55 patients with autoimmune cytopenia and 61 patients with clinical or serologic autoimmune expression, excluding autoimmune cytopenia. We clarify previous reports and we confirm a very significant correlation between an increased proportion of CD21(low) B cells and CVID associated autoimmune cytopenia, but independently of the presence of other autoimmune disorders or of splenomegaly. Moreover, in CVID associated autoimmune cytopenia, T cells display an activated phenotype with an increase of HLA-DR and CD95 expression and a decrease in the naïve T cell numbers. Patients with other autoimmune manifestations do not harbour this "T and B cells phenotypic picture". In view of recent findings on CD21(low) B cells in CVID and RA, we suggest that both a restricted subset of B cells and a T cell help are required for a breakdown of B cell tolerance against membrane auto antigens in CVID.

Immunomodulation with dendritic cells and donor lymphocyte infusion converge to induce graft vs neuroblastoma reactions without GVHD after allogeneic bone marrow transplantation

BACKGROUND

Mounting evidence points to the efficacy of donor lymphocyte infusion (DLI) and immunisation with tumour-pulsed dendritic cells (DC) in generating graft vs leukaemia reactions after allogeneic bone marrow transplantation (BMT). We assessed the efficacy of DLI and DC in generating potent graft vs neuroblastoma tumour (GVT) reactions following allogeneic BMT.

METHODS

Mice bearing congenic (H2K(a)) Neuro-2a tumours were grafted with allogeneic (H2K(b)) T-cell-depleted bone marrow cells. Tumour-pulsed donor DC (DC(Neuro2a)) were inoculated (on day +7) in conjunction with donor (H2K(b)) and haploidentical (H2K(a/b)) lymphocytes.

RESULTS

Murine Neuro-2a cells elicit immune reactions as efficient as B lymphoma in major histocompatibility complex antigen-disparate mice. Lymphopenia induced by conditioning facilitates GVT, and transition to adaptive immunity is enhanced by simultaneous infusion of and DC(Neuro2a) and lymphocytes devoid of graft vs host (GVH) activity (H2K(a/b)). In variance, the efficacy of DC-mediated immunomodulation was diminished by severe graft vs host disease (GVHD), showing mechanistic dissociation and antagonising potential to GVT.

CONCLUSIONS

The GVHD is not a prerequisite to induce GVT reactivity after allogeneic BMT, but is rather detrimental to induction of anti-tumour immunity by DC-mediated immunomodulation. Simultaneous inoculation of tumour-pulsed donor DC and DLI synergise in stimulation of potent GVT reactions to the extent of eradication of established NB tumours.

Immunosuppressive therapy exacerbates autoimmunity in NOD mice and diminishes the protective activity of regulatory T cells

Mounting evidence indicates that immunosuppressive therapy and autologous bone marrow transplantation are relatively inefficient approaches to treat autoimmune diabetes. In this study we assessed the impact of immunosuppression on inflammatory insulitis in NOD mice, and the effect of radiation on immunomodulation mediated by adoptive transfer of various cell subsets. Sublethal radiation of NOD females at the age of 14 weeks (onset of hyperglycemia) delayed the onset of hyperglycemia, however two thirds of the mice became diabetic. Adoptive transfer of splenocytes into irradiated NON and NOD mice precipitated disease onset despite increased contents of CD25(+)FoxP3(+) T cells in the pancreas and regional lymphatics. Similar phenotypic changes were observed when CD25(+) T cells were infused after radiation, which also delayed disease onset without affecting its incidence. Importantly, irradiation increased the susceptibility to diabetes in NOD and NON mice (71-84%) as compared to immunomodulation with splenocytes and CD25(+) T cells in naïve recipients (44-50%). Although irradiation had significant and durable influence on pancreatic infiltrates and the fractions of functional CD25(+)FoxP3(+) Treg cells were elevated by adoptive cell transfer, this approach conferred no protection from disease progression. Irradiation was ineffective both in debulking of pathogenic clones and in restoring immune homeostasis, and the consequent homeostatic expansion evolves as an unfavorable factor in attempts to restore self-tolerance and might even provoke uncontrolled proliferation of pathogenic clones. The obstacles imposed by immunosuppression on abrogation of autoimmune insulitis require replacement of non-specific immunosuppressive therapy by selective immunomodulation that does not cause lymphopenia.

Understanding the genetic regulation of IgE production

Immunoglobulin E (IgE) is a key mediator of anti-parasitic and anti-tumour immunity. However it is also a critical component of atopic and autoimmune diseases, and elevated serum IgE levels are a common indicator of immune dysregulation. In this review we survey the literature on genetic associations of elevated IgE in humans and mice. We find that defects in a limited number of pathways explain the majority of gene associations with IgE. Commonly, elevated IgE is associated with defects in Th bias and B cell class switching, severe T cell tolerance defects and defects in immunity at the host-environment interface. These genetic data demonstrate the mechanisms of control over IgE production and the manner in which they can be circumvented.

Epidermal and dermal dendritic cells display differential activation and migratory behavior while sharing the ability to stimulate CD4+ T cell proliferation in vivo

Migrated Langerhans cells (m-LCs) have recently been shown to comprise only a minority of skin-derived dendritic cells (DCs) expressing Langerin in cutaneous lymph nodes. We have used BM chimeric mice that differ in CD45 and MHC class II alleles to unequivocally distinguish between radioresistant m-LCs and radiosensitive migrated dermal DCs (m-dDCs), to determine their phenotype, response to contact sensitization, and ability to activate naive CD4+ T cells in vivo. We have also characterized three subsets of dDCs and their migratory counterparts, as distinguished by expression of CD11b and Langerin. Each of the four subsets of skin DCs showed differential migration to draining LN in response to contact sensitizing agents. Migration of Langerin-CD11b+ and Langerin+CD11blow dDCs peaked after 1 day, followed by Langerin-CD11blow dDCs at 2 days and Langerin+ LCs at 4 days. Moreover, while m-LCs and m-dDCs had similar surface phenotypes in the steady state, they displayed unexpectedly different activation responses to contact sensitization: m-dDCs markedly up-regulated CD80 and CD86 at day 1, whereas only m-LCs up-regulated CD40, with delayed kinetics. Thus, m-dDCs are likely to be responsible for the initial response to skin immunization. However, when expression of cognate MHC class II was restricted to LCs and m-LCs, they were also capable of processing and presenting protein Ag to drive naive CD4 T cell proliferation in vivo. Thus, m-dDCs and m-LCs display distinct behavior in cutaneous lymph nodes while sharing the ability to interact specifically with T cells to control the immune response.

Unravelling the association of partial T-cell immunodeficiency and immune dysregulation

Partial T-cell immunodeficiencies constitute a heterogeneous cluster of disorders characterized by an incomplete reduction in T-cell number or activity. The immune deficiency component of these diseases is less severe than that of the severe T-cell immunodeficiencies and therefore some ability to respond to infectious organisms is retained. Unlike severe T-cell immunodeficiencies, however, partial immunodeficiencies are commonly associated with hyper-immune dysregulation, including autoimmunity, inflammatory diseases and elevated IgE production. This causative association is counter-intuitive--immune deficiencies are caused by loss-of-function changes to the T-cell component, whereas the coincident autoimmune symptoms are the consequence of gain-of-function changes. This Review details the genetic basis of partial T -cell immunodeficiencies and draws on recent advances in mouse models to propose mechanisms by which a reduction in T-cell numbers or function may disturb the population-dependent balance between activation and tolerance.