Cytokine producing CD8+ T cells are correlated to MRI features of tissue destruction in MS

Regulation of IFN-γ production by ZFP36L2 in T cells is time-dependent

CD8+ T cells kill target cells by releasing cytotoxic molecules and proinflammatory cytokines, such as TNF and IFN-γ. The magnitude and duration of cytokine production are defined by posttranscriptional regulation, and critical regulator herein are RNA-binding proteins (RBPs). Although the functional importance of RBPs in regulating cytokine production is established, the kinetics and mode of action through which RBPs control cytokine production are not well understood. Previously, we showed that the RBP ZFP36L2 blocks the translation of preformed cytokine encoding mRNA in quiescent memory T cells. Here, we uncover that ZFP36L2 regulates cytokine production in a time-dependent manner. T cell-specific deletion of ZFP36L2 (CD4-cre) had no effect on T-cell development or cytokine production during early time points (2-6 h) of T-cell activation. In contrast, ZFP36L2 specifically dampened the production of IFN-γ during prolonged T-cell activation (20-48 h). ZFP36L2 deficiency also resulted in increased production of IFN-γ production in tumor-infiltrating T cells that are chronically exposed to antigens. Mechanistically, ZFP36L2 regulates IFN-γ production at late time points of activation by destabilizing Ifng mRNA in an AU-rich element-dependent manner. Together, our results reveal that ZFP36L2 employs different regulatory nodules in effector and memory T cells to regulate cytokine production.

RNA-Binding Protein Expression Alters Upon Differentiation of Human B Cells and T Cells

B cells and T cells are key players in the defence against infections and malignancies. To exert their function, B cells and T cells differentiate into effector and memory cells. Tight regulation of these differentiation processes is key to prevent their malfunction, which can result in life-threatening disease. Lymphocyte differentiation relies on the appropriate timing and dosage of regulatory molecules, and post-transcriptional gene regulation (PTR) is a key player herein. PTR includes the regulation through RNA-binding proteins (RBPs), which control the fate of RNA and its translation into proteins. To date, a comprehensive overview of the RBP expression throughout lymphocyte differentiation is lacking. Using transcriptome and proteome analyses, we here catalogued the RBP expression for human B cells and T cells. We observed that even though the overall RBP expression is conserved, the relative RBP expression is distinct between B cells and T cells. Differentiation into effector and memory cells alters the RBP expression, resulting into preferential expression of different classes of RBPs. For instance, whereas naive T cells express high levels of translation-regulating RBPs, effector T cells preferentially express RBPs that modulate mRNA stability. Lastly, we found that cytotoxic CD8+ and CD4+ T cells express a common RBP repertoire. Combined, our study reveals a cell type-specific and differentiation-dependent RBP expression landscape in human lymphocytes, which will help unravel the role of RBPs in lymphocyte function.

High-Resolution Expression Profiling of Peripheral Blood CD8+ Cells in Patients with Multiple Sclerosis Displays Fingolimod-Induced Immune Cell Redistribution

Fingolimod, a sphingosine-1-phosphate (S1P) receptor modulator, is an oral drug approved for the treatment of active relapsing-remitting multiple sclerosis (RRMS). It selectively inhibits the egress of lymphocytes from lymph nodes. We studied the changes in the transcriptome of peripheral blood CD8⁺ cells to unravel the effects at the molecular level during fingolimod therapy. We separated CD8⁺ cells from the blood of RRMS patients before the first dose of fingolimod as well as 24 h and 3 months after the start of therapy. Changes in the expression of coding and non-coding genes were measured with high-density Affymetrix Human Transcriptome Array (HTA) 2.0 microarrays. Differentially expressed genes in response to therapy were identified by t test and fold change and analyzed for their functions and molecular interactions. No gene was expressed at significantly higher or lower levels 24 h after the first administration of fingolimod compared to baseline. However, after 3 months of therapy, 861 transcripts were found to be differentially expressed, including interleukin and chemokine receptors. Some of the genes are associated to the S1P pathway, such as the receptor S1P5 and the kinase MAPK1, which were significantly increased in expression. The fingolimod-induced transcriptome changes reflect a shift in the proportions of CD8⁺ T cell subsets, with CCR7^- effector memory T cells being relatively increased in frequency in the blood of fingolimod-treated patients. In consequence, CCR7 mRNA levels were reduced by >80 % and genes involved in T cell activation and lymphocyte cytotoxicity were increased in expression. Gene regulatory programs caused by downstream S1P signaling had only minor effects.

Role of T cell-glial cell interactions in creating and amplifying central nervous system inflammation and multiple sclerosis disease symptoms

Multiple Sclerosis (MS) is an inflammatory disease of the Central Nervous System (CNS) that causes the demyelination of nerve cells and destroys oligodendrocytes, neurons and axons. Historically, MS has been thought of as a T cell-mediated autoimmune disease of CNS white matter. However, recent studies have identified gray matter lesions in MS patients, suggesting that CNS antigens other than myelin proteins may be involved during the MS disease process. We have recently found that T cells targeting astrocyte-specific antigens can drive unique aspects of inflammatory CNS autoimmunity, including the targeting of gray matter and white matter of the brain and inducing heterogeneous clinical disease courses. In addition to being a target of T cells, astrocytes play a critical role in propagating the inflammatory response within the CNS induced NF-κB signaling. Here, we will discuss the pathophysiology of CNS inflammation mediated by T cell—glial cell interactions and its contributions to CNS autoimmunity.

IFN-β and multiple sclerosis: cross-talking of immune cells and integration of immunoregulatory networks

Multiple sclerosis (MS) is characterized by autoimmune inflammation affecting the central nervous system and subsequent neurodegeneration. Historically, damage was thought to be mediated exclusively by auto-antigen-activated pro-inflammatory T cells. However, more recently, we are gaining increasing knowledge on the pathogenic role played in MS by B cells, dendritic cells and monocytes. IFN-β therapy was one the first approved therapy for MS for its ability to reduce relapse rate and MRI lesion activity and to significantly decrease risk of disability progression. IFN-β-mediated mechanisms of action, even if not completely understood, mainly rely on its multifaceted pleiotropic effects resulting in sustained anti-inflammatory properties directed toward almost every immune cell type. Here, we will discuss in detail literature data characterizing the pathogenic activity of the different immune cell subsets involved in MS pathogenesis and how IFN-β therapy regulates their function by modulating bystander responses. We believe that the effectiveness of this drug in MS treatment, even if in use for a long time, can unveil new insights on this disease and still teach a lesson to researchers in the MS field.

Relapsing-remitting central nervous system autoimmunity mediated by GFAP-specific CD8 T cells

Multiple sclerosis (MS) is an inflammatory disease of the CNS that causes the demyelination of nerve cells and destroys oligodendrocytes, neurons, and axons. Historically, MS has been thought to be a CD4 T cell-mediated autoimmune disease of CNS white matter. However, recent studies identified CD8 T cell infiltrates and gray matter lesions in MS patients. These findings suggest that CD8 T cells and CNS Ags other than myelin proteins may be involved during the MS disease process. In this article, we show that CD8 T cells reactive to glial fibrillary acidic protein (GFAP), a protein expressed in astrocytes, can avoid tolerance mechanisms and, depending upon the T cell-triggering event, drive unique aspects of inflammatory CNS autoimmunity. In GFAP-specific CD8 TCR-transgenic (BG1) mice, tissue resident memory-like CD8 T cells spontaneously infiltrate the gray matter and white matter of the CNS, resulting in a relapsing-remitting CNS autoimmunity. The frequency, severity, and remissions from spontaneous disease are controlled by the presence of polyclonal B cells. In contrast, a viral trigger induces GFAP-specific CD8 T effector cells to exclusively target the meninges and vascular/perivascular space of the gray and white matter of the brain, causing a rapid, acute CNS disease. These findings demonstrate that the type of CD8 T cell-triggering event can determine the presentation of distinct CNS autoimmune disease pathologies.

Mycophenolate mofetil improves neurological function and alters blood T-lymphocyte subsets in rats with experimental autoimmune encephalomyelitis

Objective

This study evaluated the clinical and pathological effects of the immunosuppressive agent mycophenolate mofetil (MMF) in rats with experimental autoimmune encephalomyelitis (EAE; a model of multiple sclerosis [MS]).

Methods

EAE rats were randomly divided into 4 groups: model alone ( n = 7); low- or high-dose MMF (20 and 30 mg/kg per day, respectively, n = 6 each) orally for 14 days; methylprednisolone (20 mg/kg per day, n = 6) injected once daily for 3 days. Six normal Wistar rats served as controls. Clinical signs and histopathological findings were evaluated 14 days after treatment started.

Results

Oral administration of high-dose MMF significantly ameliorated the course of EAE in rats: cumulative clinical scores were lower and weight loss was less than in rats receiving methylprednisolone. The ameliorated disease course was associated with alleviation of histopathological signs of EAE. Treatment increased the blood proportion of CD8+, CD4+CD25+ and CD4+CD45RA+ T cells, with a concomitant reduced proportion of CD4+ T cells and ratio of CD4+ to CD8+ T cells, compared with EAE model alone rats.

Conclusions

MMF may have pharmacological potential in MS treatment and these findings may help in understanding the pathophysiological mechanism of MS.

Immunopathogenesis and immunotherapeutic approaches in multiple sclerosis

Multiple sclerosis is an organ-specific autoimmune disease, characterized pathologically by cell-mediated inflammation, demyelination and variable degrees of axonal loss. Although inflammation is considered central to the pathogenesis of multiple sclerosis, to date, the only licensed and hence widely used multiple sclerosis immunotherapies are interferon-beta, glatiramer acetate and mitoxantrone. This review discusses the immunopathogenesis of multiple sclerosis, focusing on a number of emerging immunotherapies. A number of new approaches likely to manipulate the immunopathogenesis of multiple sclerosis and which may ultimately allow for the development of more effective immunotherapy are also highlighted.

Pathogenic CD8 T cells in multiple sclerosis and its experimental models

A growing body of evidence suggests that autoreactive CD8 T cells contribute to the disease process in multiple sclerosis (MS). Lymphocytes in MS plaques are biased toward the CD8 lineage, and MS patients harbor CD8 T cells specific for multiple central nervous system (CNS) antigens. Currently, there are relatively few experimental model systems available to study these pathogenic CD8 T cells in vivo. However, the few studies that have been done characterizing the mechanisms used by CD8 T cells to induce CNS autoimmunity indicate that several of the paradigms of how CD4 T cells mediate CNS autoimmunity do not hold true for CD8 T cells or for patients with MS. Thus, myelin-specific CD4 T cells are likely to be one of several important mechanisms that drive CNS disease in MS patients. The focus of this review is to highlight the current models of pathogenic CNS-reactive CD8 T cells and the molecular mechanisms these lymphocytes use when causing CNS inflammation and damage. Understanding how CNS-reactive CD8 T cells escape tolerance induction and induce CNS autoimmunity is critical to our ability to propose and test new therapies for MS.

Contribution of CD8 T lymphocytes to the immuno-pathogenesis of multiple sclerosis and its animal models

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) characterized by multi-focal demyelination, axonal loss, and immune cell infiltration. Numerous immune mediators are detected within MS lesions, including CD4(+) and CD8(+) T lymphocytes suggesting that they participate in the related pathogenesis. Although CD4(+) T lymphocytes are traditionally considered the main actors in MS immunopathology, multiple lines of evidence suggest that CD8(+) T lymphocytes are also implicated in the pathogenesis. In this review, we outline the recent literature pertaining to the potential roles of CD8(+) T lymphocytes both in MS and its animal models. The CD8(+) T lymphocytes detected in MS lesions demonstrate characteristics of activated and clonally expanded cells supporting the notion that these cells actively contribute to the observed injury. Moreover, several experimental in vivo models mediated by CD8(+) T lymphocytes recapitulate important features of the human disease. Whether the CD8(+) T cells can induce or aggravate tissue destruction in the CNS needs to be fully explored. Strengthening our understanding of the pathogenic potential of CD8(+) T cells in MS should provide promising new avenues for the treatment of this disabling inflammatory disease.

Upregulation of K2P5.1 potassium channels in multiple sclerosis

OBJECTIVE

Activation of T cells critically depends on potassium channels. We here characterize the impact of K(2P)5.1 (KCNK5; TASK2), a member of the 2-pore domain family of potassium channels, on T-cell function and demonstrate its putative relevance in a T-cell-mediated autoimmune disorder, multiple sclerosis (MS).

METHODS

Expression of K(2P)5.1 was investigated on RNA and protein level in different immune cells and in MS patients' biospecimens (peripheral blood mononuclear cells, cerebrospinal fluid cells, brain tissue specimen). Functional consequences of K(2P)5.1 expression were analyzed using pharmacological modulation, small interfering RNA (siRNA), overexpression, electrophysiological recordings, and computer modeling.

RESULTS

Human T cells constitutively express K(2P)5.1. After T-cell activation, a significant and time-dependent upregulation of K(2P)5.1 channel expression was observed. Pharmacological blockade of K(2P)5.1 or knockdown with siRNA resulted in reduced T-cell functions, whereas overexpression of K(2P)5.1 had the opposite effect. Electrophysiological recordings of T cells clearly dissected K(2P)5.1-mediated effects from other potassium channels. The pathophysiological relevance of these findings was demonstrated by a significant K(2P)5.1 upregulation in CD4(+) and CD8(+) T cells in relapsing/remitting MS (RRMS) patients during acute relapses as well as higher levels on CD8(+) T cells of clinically isolated syndrome, RRMS, and secondary progressive multiple sclerosis patients during clinically stable disease. T cells in the cerebrospinal fluid from MS patients exhibit significantly elevated K(2P)5.1 levels. Furthermore, K(2P)5.1-positive T cells can be found in inflammatory lesions in MS tissue specimens.

INTERPRETATION

Selective targeting of K(2P)5.1 may hold therapeutic promise for MS and putatively other T-cell-mediated disorders.

Novel therapeutic strategies for multiple sclerosis--a multifaceted adversary

Therapeutic strategies for multiple sclerosis have radically changed in the past 15 years. Five regulatory-approved immunomodulatory agents are reasonably effective in the treatment of relapsing-remitting multiple sclerosis, and appear to delay the time to progression to disabling stages. Inhibiting disease progression remains the central challenge for the development of improved therapies. As understanding of the immunopathogenesis of multiple sclerosis has advanced, a number of novel potential therapeutics have been identified, and are discussed here. It has also become apparent that traditional views of multiple sclerosis simply as a CD4+ T-cell-mediated disease of the central nervous system are incomplete. The pathogenic role of other immune components such as the innate immune system, regulatory T cells, T helper 17 cells and B cells is reaching centre stage, opening up exciting avenues and novel potential targets to affect the natural course of multiple sclerosis.

Blood CD8+ T cell responses against myelin determinants in multiple sclerosis and healthy individuals

Patients with multiple sclerosis (MS) display significant peripheral blood CD8(+) T cell receptor biases, suggesting clonal selection. Our objective was to identify relevant myelin-derived peptides capable of eliciting responses of fresh blood CD8+ T cells in MS patients. We focused our analysis on the HLA supertypes (HLA-A3, -A2, -B7, -B27, -B44) predominant in a patient cohort. Three myelin protein (MBP, PLP and MOG) sequences were screened for HLA binding motifs and peptides were tested for their binding to HLA molecules. The cellular responses of 27 MS patients and 19 age- and sex-matched healthy controls (HC) were tested in IFN-gamma ELISPOT assays only detecting pre-committed CD8+ T cells. Sixty-nine new epitopes elicited positive responses, with MOG-derived peptides being the most immunogenic and peptides binding to HLA-A3 being the most frequent. However, MS patients and HC displayed the same frequency of autoreactive cells. The epitopes inducing the strongest responses were not those with the highest HLA binding, suggesting an effective thymic selection in MS patients. Our data extend the concept that the frequency of myelin-reactive T cells in MS patient blood is not increased compared to HC. The description of this set of myelin-derived peptides (MHC class I restricted, recognized by CD8+ T cells) offers new tools to explore the CD8+ cell role in MS.

An antigen-specific pathway for CD8 T cells across the blood-brain barrier

CD8 T cells are nature's foremost defense in encephalitis and brain tumors. Antigen-specific CD8 T cells need to enter the brain to exert their beneficial effects. On the other hand, traffic of CD8 T cells specific for neural antigen may trigger autoimmune diseases like multiple sclerosis. T cell traffic into the central nervous system is thought to occur when activated T cells cross the blood-brain barrier (BBB) regardless of their antigen specificity, but studies have focused on CD4 T cells. Here, we show that selective traffic of antigen-specific CD8 T cells into the brain occurs in vivo and is dependent on luminal expression of major histocompatibility complex (MHC) class I by cerebral endothelium. After intracerebral antigen injection, using a minimally invasive technique, transgenic CD8 T cells only infiltrated the brain when and where their cognate antigen was present. This was independent of antigen presentation by perivascular macrophages. Marked reduction of antigen-specific CD8 T cell infiltration was observed after intravenous injection of blocking anti–MHC class I antibody. These results expose a hitherto unappreciated route by which CD8 T cells home onto their cognate antigen behind the BBB: luminal MHC class I antigen presentation by cerebral endothelium to circulating CD8 T cells. This has implications for a variety of diseases in which antigen-specific CD8 T cell traffic into the brain is a beneficial or deleterious feature.

Effectors of demyelination and remyelination in the CNS: implications for multiple sclerosis

Most of the research on multiple sclerosis (MS) has focused on the early events that trigger demyelination and subsequent remyelination. Less attention has been given to the factors that directly mediate the demyelination that is the hallmark of the disease. Effector cells or molecules are those factors directly responsible for mediating the damage in the disease. Similarly, there are effector molecules that are critical for remyelination in the central nervous system (CNS). By understanding those effector molecules in demyelination and remyelination that directly influence the pathologic process, we should be able to generate specific therapies with the greatest potential for benefiting MS patients. This review focuses on effector cells and molecules that are critical for demyelination and remyelination in MS but also in experimental models of the disease including experimental autoimmune encephalomyelitis (EAE), virus-induced models of demyelination (Theiler's virus, murine hepatitis virus), and toxic models of demyelination (lysolecithin, ethidium bromide, and cuprizone). These are models in which the effector molecules for demyelination and remyelination have been most precisely evaluated.

The CD8 T cell in multiple sclerosis: suppressor cell or mediator of neuropathology?

Multiple sclerosis (MS) is the most common human demyelinating disease of the central nervous system. It is universally accepted that the immune system plays a major role in the pathogenesis of MS. For decades, CD4 T cells have been considered the predominant mediator of neuropathology in MS. This perception was largely due to the similarity between MS and CD4 T-cell-driven experimental allergic encephalomyelitis, the most commonly studied murine model of MS. Over the last decade, several new observations in MS research imply an emerging role for CD8 T cells in neuropathogenesis. In certain experimental autoimmune encephalomyelitis (EAE) models, CD8 T cells are considered suppressors of pathology, whereas in other EAE models, neuropathology can be exacerbated by adoptive transfer of CD8 T cells. Studies using the Theiler's murine encephalomyelitis virus (TMEV) model have demonstrated preservation of motor function and axonal integrity in animals deficient in CD8 T cells or their effector molecules. CD8 T cells have also been demonstrated to be important regulators of blood-brain barrier permeability. There is also an emerging role for CD8 T cells in human MS. Human genetic studies reveal an important role for HLA class I molecules in MS susceptibility. In addition, neuropathologic studies demonstrate that CD8 T cells are the most numerous inflammatory infiltrate in MS lesions at all stages of lesion development. CD8 T cells are also capable of damaging neurons and axons in vitro. In this chapter, we discuss the neuropathologic, genetic, and experimental evidence for a critical role of CD8 T cells in the pathogenesis of MS and its most frequently studied animal models. We also highlight important new avenues for future research.

CD8+ T cell activation correlates with disease activity in clinically isolated syndromes and is regulated by interferon-beta treatment

An increased percentage of blood CD8+ T cells from patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) was found to express CD26 and CD69. The percentage of CD26 or CD69 positive CD8+ T cells was higher in patients with MRI evidence of disease dissemination in space or with active MRI lesions than in the remaining patients. Treatment of MS with interferon (IFN)-beta resulted in a decrease in the percentage of CD26 and CD71 positive CD8+ T cells and an increase in the percentage of CD8+ T cells that expressed interleukin (IL)-10 and IL-13. CD8+ T cell activation in MS may be linked to disease activity already at disease onset, and is regulated by treatment with IFN-beta.

A Pathogenic Role for CD8+ T Cells in a Spontaneous Model of Demyelinating Disease

Transgenic (Tg) mice that overexpress the costimulatory ligand B7.2/CD86 on microglia spontaneously develop a T cell-mediated demyelinating disease. Characterization of the inflammatory infiltrates in the nervous tissue revealed a predominance of CD8+ T cells, suggesting a prominent role of this T cell subset in the pathology. In this study, we show that the same neurological disease occurred in Tg mice deficient in the generation of CD4+ T cells, with an earlier time of onset. Analysis of the CD8+ T cell repertoire at early stage of disease revealed the presence of selected clonal expansions in the CNS but not in peripheral lymphoid organs. We further show that Tg animals deficient in IFN-gamma receptor expression were completely resistant to disease development. Microglia activation that is an early event in disease development is IFN-gamma dependent and thus appears as a key element in disease pathogenesis. Collectively, our data indicate that the spontaneous demyelinating disease in this animal model occurs as a consequence of an inflammatory response initiated through the activation of CNS-specific CD8+ T cells by Tg expression of B7.2 within the target organ. Thus, autoreactive CD8+ T cells can contribute directly to the pathogenesis of neuroinflammatory diseases such as multiple sclerosis.

Intrathecal synthesis of soluble HLA-G and HLA-I molecules are reciprocally associated to clinical and MRI activity in patients with multiple sclerosis

The aim of this study was to provide further insight into the effective contribution of classical soluble HLA-A, B and C class Ia (sHLA-I) and non-classical soluble HLA-G class Ib (sHLA-G) molecules in immune dysregulation occurring in multiple sclerosis (MS). We evaluated by enzyme-linked immunosorbent assay (ELISA) technique intrathecal synthesis and cerebrospinal fluid (CSF) and serum levels of sHLA-I and sHLA-G in 69 relapsing-remitting (RR), 21 secondary progressive (SP) and 13 primary progressive (PP) MS patients stratified according to clinical and magnetic resonance imaging (MRI) evidence of disease activity. We also tested, as neurological controls, 91 patients with other inflammatory neurological disorders (OIND) and 92 with non-inflammatory neurological disorders (NIND). Eighty-two healthy volunteers served as further controls for sHLA-I and sHLA-G determinations. An intrathecal production of sHLA-I and sHLA-G detected by specific indexes was significantly more frequent in MS patients than in controls (P<0.01). An intrathecal synthesis of sHLA-I was prevalent in clinically (P<0.02) and MRI active (P<0.001) MS, whereas a CSF-restricted release of sHLA-G predominated in clinically (P<0.01) and MRI stable (P<0.001) MS. sHLA-I levels were low in the serum of clinically active (P<0.001) and high in the CSF of MRI active (P<0.01) MS. Conversely, sHLA-G concentrations were decreased in the serum of clinically stable MS (P<0.01) and increased in the CSF of MRI inactive MS (P<0.001). The trends towards a negative correlation observed between CSF and serum concentrations and intrathecal synthesis of sHLA-I and sHLA-G in patients without evidence of clinical and MRI activity confirmed that intrathecal production and fluctuations in CSF and serum concentrations of sHLA-I and sHLA-G were reciprocal in MS. Our results suggest that, in MS, a balance between classical sHLA-I and non-classical sHLA-G products modulating both MRI and clinical disease activity in opposite directions may exist.

Long-term favorable response to interferon beta-1b is linked to cytokine deviation toward the Th2 and Tc2 sides in Japanese patients with multiple sclerosis

To address the immune mechanism of the long-term beneficial effects of interferon beta (IFN-beta), we measured the intracellular cytokine production patterns of IFN-gamma, IL-4 and IL-13 in peripheral blood CD4+ and CD8+ T cells, which previously displayed alterations during the early course of IFN-beta treatment, in 15 Japanese patients after long-term IFN-beta administration. The patients were treated with IFN-beta-1b 8 x 10(6) units given subcutaneously every other day for a mean period of 34.5 +/- 5.5 months (range: 26-43 months). During the follow-up period, 6 patients experienced 33 relapses, while the other 9 were relapse-free. The results revealed the following cytokine alterations: (1) type 2 cytokine, such as IL-4 and IL-13, were significantly increased in producing cell percentages in both CD4+ (p = 0.0356 and p = 0.0007, respectively) and CD8+ (p = 0.0231 and p = 0.0170, respectively) T cells while IFN-gamma, a representative type 1 cytokine, was significantly decreased in the absolute producing cell numbers (p = 0.0125 in CD4+ T cells and p = 0.0022 in CD8+ T cells) even after approximately 3 years of IFN-beta administration; (2) the intracellular IFN-gamma / IL-4 ratio tended to decrease in both CD4+ and CD8+ T cells (p = 0.0535 and p = 0.0783, respectively), reflecting a strong downmodulation of type 1 cytokine producing cells; and importantly (3) alterations such as the decreased intracellular IFN-gamma / IL-4 ratio in CD4+ T cells and increased percentage of CD8+ IL-13+ T cells compared with the pretreatment levels were only statistically significant in MS patients without relapse during IFN-beta therapy (p = 0.0152 and p = 0.0078, respectively). Therefore, we consider that cytokine deviation toward the Th2 and Tc2 sides is linked to a long-term favorable response to IFN-beta, while a higher intracellular IFN-gamma / IL-4 ratio is associated with treatment failure.

Sex differences in proinflammatory cytokine profiles of progressive patients in multiple sclerosis

The objective of this article is to evaluate the presence of sex differences in expression of cytokines in both CD4+ and CD8+ T cells derived from peripheral blood of untreated multiple sclerosis (MS) patients. The predominance of females in MS and other autoimmune diseases may be related to their differential responses in many immunological settings. Recent data show beneficial effect of sex hormones on proinflammatory cytokine levels and on magnetic resonance imaging in MS. Better understanding of gender differences is warranted. In this study 124 MS subjects (M:F; 56:68) and 34 healthy controls (M:F; 12:22) were included. Stimulated peripheral blood-derived CD4+ and CD8+ T cells were analysed for interferon-gamma, interleukin (IL)-2, tumour necrosis factor alpha, IL-4, IL- 10 and IL- 13 production. There were no significant differences for these cytokines between male and female MS subjects in the whole group. Compared to males, female patients had higher proinflammatory cytokine levels in the progressive phase of the disease. In conclusion, the data presented indicate that cytokine production and sex differences in cytokine production might differ between disease phases, probably related to underlying disease mechanisms.

The activation of memory CD4+ T cells and CD8+ T cells in patients with multiple sclerosis

To reevaluate whether an association exists between the clinical course of multiple sclerosis (MS) and the activation of memory T cells, we investigated the phenotype of T cells in peripheral blood and cerebrospinal fluid (CSF) of patients with MS using five-color flow cytometry. A cross-sectional study with 39 relapsing-remitting MS patients demonstrated that the percentage of CD25(+)CD45RO(+)CD4(+)CD3(+) cells was significantly increased in peripheral blood as well as in CSF of active MS patients compared with inactive MS patients. A longitudinal study with 11 relapsing-remitting MS patients also showed a higher percentage of CD25(+)CD45RO(+)CD4(+)CD3(+) cells in peripheral blood at the phase of exacerbation than during remission. On the other hand, regardless of the disease activity, the percentage of CD25(+)CD45RO(+)CD8(+)CD3(+) cells in peripheral blood was significantly higher in patients with MS than in healthy control subjects. A lower percentage of CD25(+)CD45RO(+)CD8(+)CD3(+) cells in CSF was observed in active MS patients compared with inactive MS patients. These results suggest that the activation of memory CD4(+) T cells is associated with the exacerbation of MS and activation of memory CD8(+) T cells reflects systemic immunological dysregulation in MS patients. Transient as well as continuous activation of T cells by recall antigens may be involved in the disease course of MS.

Macrophages and neurodegeneration

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Demyelination is a classical feature of MS lesions, and neurological deficits are often ascribed to the reduced signal conduction by demyelinated axons. However, recent studies emphasize that axonal loss is an important factor in MS pathogenesis and disease progression. Axonal loss is found in association with cellular infiltrates in MS lesions. In this review, we discuss the possible contribution of the innate immune system in this process. In particular, we describe how infiltrated macrophages may contribute to axonal loss in MS and in experimental autoimmune encephalomyelitis (EAE), the animal model for MS. An overview is given of the possible effects of mediators, which are produced by activated macrophages, such as such as pro-inflammatory cytokines, free radicals, glutamate and metalloproteases, on axonal integrity. We conclude that infiltrated macrophages, which are activated to produce pro-inflammatory mediators, may be interesting targets for therapeutic approaches aimed to prevent or reduce axonal loss during exacerbation of inflammation. Interference with the process of infiltration and migration of monocytes across the blood-brain barrier is one of the possibilities to reduce the damage by activated macrophages.

Immunology of multiple sclerosis

Multiple sclerosis (MS) develops in young adults with a complex predisposing genetic trait and probably requires an inciting environmental insult such as a viral infection to trigger the disease. The activation of CD4+ autoreactive T cells and their differentiation into a Th1 phenotype are a crucial events in the initial steps, and these cells are probably also important players in the long-term evolution of the disease. Damage of the target tissue, the central nervous system, is, however, most likely mediated by other components of the immune system, such as antibodies, complement, CD8+ T cells, and factors produced by innate immune cells. Perturbations in immunomodulatory networks that include Th2 cells, regulatory CD4+ T cells, NK cells, and others may in part be responsible for the relapsing-remitting or chronic progressive nature of the disease. However, an important paradigmatic shift in the study of MS has occurred in the past decade. It is now clear that MS is not just a disease of the immune system, but that factors contributed by the central nervous system are equally important and must be considered in the future.

Nitric-oxide-dependent and independent mechanisms of protection from CNS inflammation during Th1-mediated autoimmunity: evidence from EAE in iNOS KO mice

Experimental autoimmune encephalomyelitis (EAE) disease was accelerated iNOS-deficient (KO) mice: coinciding with greatly increased numbers of Ag-specific Th1 cells in the periphery that appeared to rapidly shift from the spleen to the CNS during onset of disease symptoms. iNOS KO mice had significantly increased Th1 cells in the CNS versus wild-type mice. Apoptosis of CNS-infiltrating CD4(+) T cells was impaired in iNOS KO mice at peak of disease; consequently, these mice had more CNS-infiltrating CD4(+) T cells. Subsequently, iNOS KO mice up-regulated apoptosis of CNS-CD4(+) T cells. During chronic EAE, CNS macrophages were greatly decreased, suggesting elimination of CNS-infiltrating CD4(+) T cells and activated macrophages by iNOS-independent mechanisms. INOS is not only required for apoptosis of CNS-CD4(+) T cells but also prevents overexpansion of autoreactive Th1 cells in the periphery and the CNS.

Multiple sclerosis: brain-infiltrating CD8+ T cells persist as clonal expansions in the cerebrospinal fluid and blood

We surveyed the T cell receptor repertoire in three separate compartments (brain, cerebrospinal fluid, and blood) of two multiple sclerosis patients who initially had diagnostic brain biopsies to clarify their unusual clinical presentation but were subsequently confirmed to have typical multiple sclerosis. One of the brain biopsy specimens had been previously investigated by microdissection and single-cell PCR to determine the clonal composition of brain-infiltrating T cells at the single-cell level. Using complementarity-determining region 3 spectratyping, we identified several identical, expanded CD8+ (but not CD4+) T cell clones in all three compartments. Some of the expanded CD8+ T cells also occurred in sorted CD38+ blood cells, suggesting that they were activated. Strikingly, some of the brain-infiltrating CD8+ T cell clones persisted for >5 years in the cerebrospinal fluid and/or blood and may thus contribute to the progression of the disease.

Immunomonitoring measures in relapsing-remitting multiple sclerosis

Forty-five patients with relapsing-remitting multiple sclerosis (MS) were examined to determine intracellular cytokine profiles and the surface phenotype of circulating lymphocytes during active, recovery, and stable stages. Active stage patients were characterized by decreases in CD4(+)IL-4(+) Th2 as well as CD4(+)IFN-gamma(+) Th1 cells, when compared with stable stage patients and 16 healthy controls. CCR4(+) Th2 cells were persistently decreased at every MS stage as compared to the controls. CD4(+)CD29(+) and CD4(+)CXCR3(+) cells were closely correlated with IFN-gamma-producing cells. These findings suggest that simultaneous flow cytometry for these two types of measurements can provide information concerning current immune status in MS.