Expansion of CD4+CD28- T cells producing high levels of interferon-{gamma} in peripheral blood of patients with multiple sclerosis

Involvement of expanded cytotoxic and proinflammatory CD28null T cells in primary Sjögren's syndrome

OBJECTIVE

The absence of CD28 is a feature of antigen-experienced, highly differentiated and aged T cells. The pathogenicity of CD28null T cells remains elusive in primary Sjögren's syndrome (pSS). Therefore, this study was performed to explore the characteristics of CD28null T cells in both peripheral blood and minor salivary glands (MSGs) of pSS patients.

METHODS

pSS patients and paired healthy controls (HCs) were enrolled. The phenotype of peripheral CD28null T cells was analyzed using flow cytometry. In vitro functional assays were performed to evaluate the cytotoxic and proinflammatory effects of peripheral CD28null T cells. In addition, polychromatic immunofluorescence staining was performed to investigate infiltrating CD28null T cells in MSGs.

RESULTS

A significant expansion of peripheral CD28null T cells was observed in pSS patients compared with HCs (p < 0.001), which were primarily CD8+CD28null T cells. The proportion of peripheral CD8+CD28null T cells moderately correlated with the erythrocyte sedimentation rate (r = 0.57, p < 0.01) and IgG levels (r = 0.44, p < 0.01). Peripheral CD28null T cells had stronger capacities to secrete granzyme B and perforin, but comparable capacities to secrete IFN-γ and TNF-α than their CD28+ counterparts. An abundant amount of cytotoxic and pro-inflammatory CD28null T cells was also found in MSGs. Moreover, a high expression of the chemokine receptor CXCR3 was found on peripheral and tissue-resident CD28null T cells, with its ligands CXCL9/10 abundantly present in MSGs.

CONCLUSION

Increasing CD28null T cells with strong cytotoxicity and proinflammatory effects were observed in both peripheral blood and MSGs from pSS patients. The precise mechanism of action and migration still needs further investigation.

Changes in serum cytokine profile and deficit severity in patients with relapsing-remitting multiple sclerosis

INTRODUCTION

In experimental autoimmune encephalomyelitis, neurological deficit correlates with axonal loss and the CD8+ T cells are a likely mediator of axonal damage. In relapsing-remitting multiple sclerosis, there is a correlation of the immune inflammatory activity in the lesion foci with the axon transection.

T-cell senescence: A crucial player in autoimmune diseases

Senescent T cells are proliferative disabled lymphocytes that lack antigen-specific responses. The development of T-cell senescence in autoimmune diseases contributes to immunological disorders and disease progression. Senescent T cells lack costimulatory markers with the reduction of T cell receptor repertoire and the uptake of natural killer cell receptors. Senescent T cells exert cytotoxic effects through the expression of perforin, granzymes, tumor necrosis factor, and other molecules without the antigen-presenting process. DNA damage accumulation, telomere damage, and limited DNA repair capacity are important features of senescent T cells. Impaired mitochondrial function and accumulation of reactive oxygen species contribute to T cell senescence. Alleviation of T-cell senescence could provide potential targets for the treatment of autoimmune diseases.

First report of expansion of CD4+/CD28 null T-helper lymphocytes in adult patients with idiopathic autoimmune hemolytic anemia

CD28 null T helper (T_h) cells are rare in healthy individuals, but they are increased in various inflammatory and immune-mediated diseases. In this study, we determined the size of the CD4⁺/CD28 null T lymphocyte compartment in the peripheral blood of 40 autoimmune hemolytic anemia (AIHA) patients (idiopathic and secondary) and 20 healthy control subjects, using tri-color flow cytometry. The frequency and absolute count of CD4⁺/CD28 null T helper (T_h) cells was significantly higher in idiopathic AIHA patients, compared to healthy controls (p = 0.001 and 0.001, respectively) and to patients with secondary AIHA (p = 0.04 and 0.01, respectively). The percentage of CD4⁺/CD28 null T_h cells was also negatively correlated to the hemoglobin (Hb) level (p = 0.03). These findings demonstrate, for the first time, the expansion of this phenotypically-defined population of T lymphocytes in patients with idiopathic AIHA and indicate that it likely plays an etiological role in the development of this disease. However, establishing the use of this marker for diagnosis or monitoring treatment of such patients needs further studies.

CD28 null CD4 T-cell expansions in autoimmune disease suggest a link with cytomegalovirus infection

Immunosenescence is thought to contribute to the increase of autoimmune diseases in older people. Immunosenescence is often associated with the presence of an expanded population of CD4 T cells lacking expression of CD28 (CD28 ^null). These highly cytotoxic CD4 T cells were isolated from disease-affected tissues in patients with rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, or other chronic inflammatory diseases and their numbers appeared to be linked to disease severity. However, we recently demonstrated that the common herpes virus, cytomegalovirus (CMV), not ageing, is the major driver of this subset of cytotoxic T cells. In this review, we discuss how CMV might potentiate and exacerbate autoimmune disease through the expansion of CD28 ^null CD4 T cells.

Antithymocyte globulins in renal transplantation-from lymphocyte depletion to lymphocyte activation: The doubled-edged sword

Compelling data suggest that lymphocyte depletion following T cell depleting therapy may induce prolonged CD4 T cell lymphopenia and trigger lymphocyte activation in some patients. These profound and non-reversible immune changes in T cell pool subsets are the consequence of both impaired thymic renewal and peripheral homeostatic proliferation. Chronic viral challenges by CMV play a major role in these immune alterations. Even when the consequences of CD4 T cell lymphopenia have been now well described, recent studies shed new light on the clinical consequences of immune activation. In this review, we will first focus on the mechanisms involved in T cell pool reconstitution after T cell depletion and further consider the clinical consequences of ATG-induced T cell activation and senescence in renal transplant recipients.

Interferon-gamma potentiates NMDA receptor signaling in spinal dorsal horn neurons via microglia-neuron interaction

BACKGROUND

Glia-neuron interactions play an important role in the development of neuropathic pain. Expression of the pro-inflammatory cytokne →cytokine Interferon-gamma (IFNγ) is upregulated in the dorsal horn after peripheral nerve injury, and intrathecal IFNγ administration induces mechanical allodynia in rats. A growing body of evidence suggests that IFNγ might be involved in the mechanisms of neuropathic pain, but its effects on the spinal dorsal horn are unclear. We performed blind whole-cell patch-clamp recording to investigate the effect of IFNγ on postsynaptic glutamate-induced currents in the substantia gelatinosa neurons of spinal cord slices from adult male rats.

RESULTS

IFNγ perfusion significantly enhanced the amplitude of NMDA-induced inward currents in substantia gelatinosa neurons, but did not affect AMPA-induced currents. The facilitation of NMDA-induced current by IFNγ was inhibited by bath application of an IFNγ receptor-selective antagonist. Adding the Janus activated kinase inhibitor tofacitinib to the pipette solution did not affect the IFNγ-induced facilitation of NMDA-induced currents. However, the facilitatory effect of IFNγ on NMDA-induced currents was inhibited by perfusion of the microglial inhibitor minocycline. These results suggest that IFNγ binds the microglial IFNγ receptor and enhances NMDA receptor activity in substantia gelatinosa neurons. Next, to identify the effector of signal transmission from microglia to dorsal horn neurons, we added an inhibitor of G proteins, GDP-β-S, to the pipette solution. In a GDP-β-S-containing pipette solution, IFNγ-induced potentiation of the NMDA current was significantly suppressed after 30 min. In addition, IFNγ-induced potentiation of NMDA currents was blocked by application of a selective antagonist of CCR2, and its ligand CCL2 increased NMDA-induced currents.

CONCLUSION

Our findings suggest that IFNγ enhance the amplitude of NMDA-induced inward currents in substantia gelatinosa neurons via microglial IFNγ receptors and CCL2/CCR2 signaling. This mechanism might be partially responsible for the development of persistent neuropathic pain.

Secondary Progression in Multiple Sclerosis: Neuronal Exhaustion or Distinct Pathology?

Prevention of progression in neurological diseases, particularly in multiple sclerosis (MS) but also in neurodegenerative diseases, remains a significant challenge. MS patients switch from a relapsing-remitting to a progressive disease course, but it is not understood why and how this conversion occurs and why some patients never experience disease progression. Do aging and accumulation of neuronal damage induce progression, or do cognitive symptoms and accelerated grey matter (GM) atrophy point to distinct processes affecting networks? This review weighs accepted dogma against real data on the secondary progressive phase of the disease, highlighting current challenges in this important field and directions towards development of treatment strategies to slow or prevent progression of disability.

N-Terminally extended analogues of the K⁺ channel toxin from Stichodactyla helianthus as potent and selective blockers of the voltage-gated potassium channel Kv1.3

The voltage-gated potassium channel Kv1.3 is an important target for the treatment of autoimmune diseases and asthma. Blockade of Kv1.3 by the sea anemone peptide K⁺-channel toxin from Stichodactyla helianthus (ShK) inhibits the proliferation of effector memory T lymphocytes and ameliorates autoimmune diseases in animal models. However, the lack of selectivity of ShK for Kv1.3 over the Kv1.1 subtype has driven a search for Kv1.3-selective analogues. In the present study, we describe N-terminally extended analogues of ShK that contain a negatively-charged Glu, designed to mimic the phosphonate adduct in earlier Kv1.3-selective analogues, and consist entirely of common protein amino acids. Molecular dynamics simulations indicated that a Trp residue at position [-3] of the tetrapeptide extension could form stable interactions with Pro377 of Kv1.3 and best discriminates between Kv1.3 and Kv1.1. This led to the development of ShK with an N-terminal Glu-Trp-Ser-Ser extension ([EWSS]ShK), which inhibits Kv1.3 with an IC₅₀ of 34 pm and is 158-fold selective for Kv1.3 over Kv1.1. In addition, [EWSS]ShK is more than 2900-fold more selective for Kv1.3 over Kv1.2 and KCa3.1 channels. As a highly Kv1.3-selective analogue of ShK based entirely on protein amino acids, which can be produced by recombinant expression, this peptide is a valuable addition to the complement of therapeutic candidates for the treatment of autoimmune diseases.

ATG-induced accelerated immune senescence: clinical implications in renal transplant recipients

Persistent ATG-induced CD4(+) T cell lymphopenia is associated with serious clinical complications. We tested the hypothesis that ATG induces accelerated immune senescence in renal transplant recipients (RTR). Immune senescence biomarkers were analyzed at transplant and one-year later in 97 incident RTR -62 patients receiving ATG and 35 receiving anti-CD25 mAb (α-CD25). This consisted in: (i) thymic output; (ii) bone marrow renewal of CD34(+) hematopoietic progenitor cells (CD34(+) HPC) and lymphoid (l-HPC) and myeloid (m-HPC) progenitor ratio; (iii) T cell phenotype; and (iv) measurement of T cell relative telomere length (RTL) and telomerase activity (RTA). Clinical correlates were analyzed with a 3 year follow-up. Thymic output significantly decreased one-year posttransplant in ATG-treated patients. ATG was associated with a significant decrease in l-HPC/m-HPC ratio. Late stage differentiated CD57(+) /CD28(-) T cells increased in ATG-treated patients. One-year posttransplant T cell RTL and RTA were consequently lower in ATG-treated patients. ATG is associated with accelerated immune senescence. Increased frequency of late differentiated CD4(+) T cell frequency at transplantation tended to be predictive of a higher risk of subsequent opportunistic infections and of acute rejection only in ATG-treated patients but this needs confirmation. Considering pretransplant immune profile may help to select those patients who may benefit from ATG to prevent severe infections and acute rejection.

Pathogenic features of CD4+CD28- T cells in immune disorders

Aging of the immune system contributes to the increased morbidity and mortality of the elderly population and may occur prematurely in patients with immune disorders. One of the main characteristics of immunosenescence is the expansion of CD4(+)CD28(-) T cells in the blood. These cells are effector memory T cells with cytotoxic capacity, and have been recently described to have pathogenic potential in a variety of immune disorders. Interestingly, CD4(+)CD28(-) T cells have now been found to infiltrate target tissues of patients with multiple sclerosis, rheumatoid arthritis, myopathies, acute coronary syndromes, and other immune-related diseases. In this review, we discuss potential factors and mechanisms that may induce the expansion of these cells, as well as their putative pathogenic mechanisms in immune disorders.

Self-tolerance in multiple sclerosis

During the last decade, several defects in self-tolerance have been identified in multiple sclerosis. Dysfunction in central tolerance leads to the thymic output of antigen-specific T cells with T cell receptor alterations favouring autoimmune reactions. In addition, premature thymic involution results in a reduced export of naïve regulatory T cells, the fully suppressive clone. Alterations in peripheral tolerance concern costimulatory molecules as well as transcriptional and epigenetic mechanisms. Recent data underline the key role of regulatory T cells that suppress Th1 and Th17 effector cell responses and whose immunosuppressive activity is impaired in patients with multiple sclerosis. Those recent observations suggest that a defect in self-tolerance homeostasis might be the primary mover of multiple sclerosis leading to subsequent immune attacks, inflammation and neurodegeneration. The concept of multiple sclerosis as a consequence of the failure of central and peripheral tolerance mechanisms to maintain a self-tolerance state, particularly of regulatory T cells, may have therapeutic implications. Restoring normal thymic output and suppressive functions of regulatory T cells appears an appealing approach. Regulatory T cells suppress the general local immune response via bystander effects rather than through individual antigen-specific responses. Interestingly, the beneficial effects of currently approved immunomodulators (interferons β and glatiramer acetate) are associated with a restored regulatory T cell homeostasis. However, the feedback regulation between Th1 and Th17 effector cells and regulatory T cells is not so simple and tolerogenic mechanisms also involve other regulatory cells such as B cells, dendritic cells and CD56(bright) natural killer cells.

The CD4+ T-cell subset lacking expression of the CD28 costimulatory molecule is expanded and shows a higher activation state in multiple sclerosis

Multiple sclerosis (MS) is a chronic debilitating disease, in which T-cells are considered to play a pivotal role. CD28 is the quintessential costimulatory molecule on T-cells and its expression declines progressively with repeated stimulations, leading to the generation of CD28(-) T-cells. Our aim was to examine whether CD4(+)CD28(-) T-cells were enriched in MS patients, and characterize the phenotype of this subset in MS patients and healthy controls (HC). All these changes could provide these CD4(+)CD28(-) T-cell characteristics that might be involved in the pathogenesis of MS, turning this T-cell subset into a potential target for future therapeutic strategies.

CX(3)CR1 drives cytotoxic CD4(+)CD28(-) T cells into the brain of multiple sclerosis patients

Immunosenescence, or ageing of the immune system, contributes to the increased morbidity and mortality seen in the elderly population. Premature immunosenescence is shown to occur in a subgroup of patients with autoimmune diseases. One of the main characteristics of immunosenescence is the expansion of CD4(+)CD28(-) T cells in the blood. In this study, we investigate the potential contribution of these cells to disease processes in a subgroup of multiple sclerosis (MS) and rheumatoid arthritis (RA) patients. Characterization of CD4(+)CD28(-) T cells in patients and healthy controls reveals that they have an inflammation-seeking effector-memory T cell phenotype with cytotoxic properties, as they expel cytotoxic granules in response to a polyclonal stimulus or MS-related autoantigens. We identify CX(3)CR1, the fractalkine receptor, as a selective marker to discriminate CD4(+)CD28(-) T cells from their CD4(+)CD28(+) counterparts. CX(3)CR1 expression enables CD4(+)CD28(-) T cells to migrate towards a fractalkine gradient in vitro. In addition, we find increased levels of fractalkine in the cerebrospinal fluid and inflammatory lesions of MS patients. We demonstrate for the first time that CD4(+)CD28(-) T cells accumulate in MS lesions of a subgroup of patients. Moreover, we have indications that these cells are cytotoxic in the target tissue. Overall, our findings suggest that CD4(+)CD28(-) T cells migrate in response to a chemotactic gradient of fractalkine to sites of inflammation, where they contribute to the inflammatory processes in a subgroup of patients with MS and RA.

Development of a sea anemone toxin as an immunomodulator for therapy of autoimmune diseases

Electrophysiological and pharmacological studies coupled with molecular identification have revealed a unique network of ion channels--Kv1.3, KCa3.1, CRAC (Orai1 + Stim1), TRPM7, Cl(swell)--in lymphocytes that initiates and maintains the calcium signaling cascade required for activation. The expression pattern of these channels changes during lymphocyte activation and differentiation, allowing the functional network to adapt during an immune response. The Kv1.3 channel is of interest because it plays a critical role in subsets of T and B lymphocytes implicated in autoimmune disorders. The ShK toxin from the sea anemone Stichodactyla helianthus is a potent blocker of Kv1.3. ShK-186, a synthetic analog of ShK, is being developed as a therapeutic for autoimmune diseases, and is scheduled to begin first-in-man phase-1 trials in 2011. This review describes the journey that has led to the development of ShK-186.

Increased peripheral blood leukocyte subsets with regulatory phenotype in clinically stable long-term HIV-infected hemophilia patients on HAART may be beneficial and contribute to a decrease in autoimmunity

After initiation of highly-active antiretroviral therapy (HAART), long-term HIV-infected hemophilia patients have been shown to lose autoantibodies against CD4(+) peripheral blood leukocytes (PBL), suggesting that HAART induces autoimmunity-blocking mechanisms. We compared cytokine levels and subpopulations of lymphocytes and dendritic cells (DC) in the blood of 40 long-term HIV(+) patients with those of 13 long-term HIV(-) hemophilia patients; 23 HIV(+) patients had a detectable retroviral load. Cell subsets were determined using flow cytometry and cytokine levels were measured using ELISA. HIV(+) patients showed higher proportions of DC subpopulations with immunostimulatory phenotypes (p < 0.01), CD8(+) PBL (p < 0.001), and IL-2 (p < 0.001) and sIL-2R plasma levels (p = 0.002) than HIV(-) patients. They also exhibited increased proportions of T PBL with immunosuppressive phenotypes such as CD3(+)CD4(+)CD25(+)Foxp3(+) (p = 0.001), and CD3(+)CD8(+)CD28(-)Foxp3(+) PBL (p < 0.001), and a decreased IL-7R expression on CD3(+)CD8(+) PBL (p = 0.001) compared to HIV(-) patients. Frequencies of CD3(+)CD4(+)CD25(+) PBL producing IL-2, IL-4, IL-10, IL-12, and/or IFN-gamma, and of CD3(+)CD4(+)CD28(-) PBL secreting IL-2 and/or IL-4 were lower in HIV(+) than in HIV(-) patients (p <or= 0.02). Proportions of CD4(+) PBL coated with IgG, IgM, and C3d were similar in HIV(+) and HIV(-) patients (p = n.s.). However, the proportion of CD4(+)gp120(+) PBL was higher in HIV(+) patients (p = 0.002), and associated with low CD3(+)CD4(+)CD25(+)Foxp3(+) PBL (p = 0.012). We conclude that long-term HIV-infected hemophilia patients on HAART show an adaptive immune response, presumably against HIV, in the presence of upregulated immunosuppressive T PBL, downregulated cytokine-producing CD4(+) PBL, and downregulated IL-7R expression on CD8(+) PBL. Increased immunoregulatory T PBL might decrease autoimmunity, thereby contributing to immunological reconstitution and stabilization of long-term HIV-infected hemophilia patients on HAART.

Longitudinal system-based analysis of transcriptional responses to type I interferons

Type I interferons (IFNs) are pleiotropic cytokines that modulate both innate and adaptive immune responses. They have been used to treat autoimmune disorders, cancers, and viral infection and have been demonstrated to elicit differential responses within cells, despite sharing a single receptor. The molecular basis for such differential responses has remained elusive. To identify the mechanisms underlying differential type I IFN signaling, we used whole genome microarrays to measure longitudinal transcriptional events within human CD4(+) T cells treated with IFN-alpha(2b) or IFN-beta(1a). We identified differentially regulated genes, analyzed them for the enrichment of known promoter elements and pathways, and constructed a network module based on weighted gene coexpression network analysis (WGCNA). WGCNA uses advanced statistical measures to find interconnected modules of correlated genes. Overall, differential responses to IFN in CD4(+) T cells related to three dominant themes: migration, antigen presentation, and the cytotoxic response. For migration, WGCNA identified subtype-specific regulation of pre-mRNA processing factor 4 homolog B and eukaryotic translation initiation factor 4A2, which work at various levels within the cell to affect the expression of the chemokine CCL5. WGCNA also identified sterile alpha-motif domain-containing 9-like (SAMD9L) as critical in subtype-independent effects of IFN treatment. RNA interference of SAMD9L expression enhanced the migratory phenotype of activated T cells treated with IFN-beta compared with controls. Through the analysis of the dynamic transcriptional events after differential IFN treatment, we were able to identify specific signatures and to uncover novel genes that may underpin the type I IFN response.

Interferon-gamma is a critical modulator of CB(2) cannabinoid receptor signaling during neuropathic pain

Nerve injuries often lead to neuropathic pain syndrome. The mechanisms contributing to this syndrome involve local inflammatory responses, activation of glia cells, and changes in the plasticity of neuronal nociceptive pathways. Cannabinoid CB(2) receptors contribute to the local containment of neuropathic pain by modulating glial activation in response to nerve injury. Thus, neuropathic pain spreads in mice lacking CB(2) receptors beyond the site of nerve injury. To further investigate the mechanisms leading to the enhanced manifestation of neuropathic pain, we have established expression profiles of spinal cord tissues from wild-type and CB(2)-deficient mice after nerve injury. An enhanced interferon-gamma (IFN-gamma) response was revealed in the absence of CB(2) signaling. Immunofluorescence stainings demonstrated an IFN-gamma production by astrocytes and neurons ispilateral to the nerve injury in wild-type animals. In contrast, CB(2)-deficient mice showed neuronal and astrocytic IFN-gamma immunoreactivity also in the contralateral region, thus matching the pattern of nociceptive hypersensitivity in these animals. Experiments in BV-2 microglia cells revealed that transcriptional changes induced by IFN-gamma in two key elements for neuropathic pain development, iNOS (inducible nitric oxide synthase) and CCR2, are modulated by CB(2) receptor signaling. The most direct support for a functional involvement of IFN-gamma as a mediator of CB(2) signaling was obtained with a double knock-out mouse strain deficient in CB(2) receptors and IFN-gamma. These animals no longer show the enhanced manifestations of neuropathic pain observed in CB(2) knock-outs. These data clearly demonstrate that the CB(2) receptor-mediated control of neuropathic pain is IFN-gamma dependent.