Cerebrospinal Fluid Of Multiple Sclerosis Patients Research Articles

Specific central nervous system recruitment of HLA‐G+ regulatory T cells in multiple sclerosis

We have recently described a novel population of natural regulatory T cells (T(reg)) that are characterized by the expression of HLA-G and may be found at sites of tissue inflammation (HLA-G(pos) T(reg)). Here we studied the role of these cells in multiple sclerosis (MS), a prototypic autoimmune inflammatory disorder of the central nervous system (CNS). Sixty-four patients with different types of MS, 9 patients with other neurological diseases, and 20 healthy donors were included in this study. Inflamed brain lesions from 5 additional untreated MS patients were examined. HLA-G(pos) T(reg) were analyzed in the cerebrospinal fluid (CSF) by flow cytometry and in inflammatory demyelinating lesions of MS brain specimens by immunohistochemistry. Functional capacity was accessed and transmigration was determined using an in vitro model of the human blood-brain barrier (BBB). HLA-G(pos) T(reg) were found enriched in the inflamed CSF of MS patients and in inflammatory demyelinating lesions of MS brain specimens. HLA-G(pos) T(reg) showed a strong propensity to transmigrate across BBB, which was vigorously driven by inflammatory chemokines, and associated with a gain of suppressive capacity upon transmigration. CSF-derived HLA-G(pos) T(reg) of MS patients represented a population of activated central memory activated T cells with an upregulated expression of inflammatory chemokine receptors and exhibiting full suppressive capacity. Unlike natural FoxP3-expressing T(reg), HLA-G(pos) T(reg) derived from peripheral blood were functionally unimpaired in MS. In MS, HLA-G(pos) T(reg) may serve to control potentially destructive immune responses directly at the sites of CNS inflammation and to counterbalance inflammation once specifically recruited to the CNS.

Up-Regulation of Soluble Axl and Mer Receptor Tyrosine Kinases Negatively Correlates with Gas6 in Established Multiple Sclerosis Lesions

Multiple sclerosis is a disease that is characterized by inflammation, demyelination, and axonal damage; it ultimately forms gliotic scars and lesions that severely compromise the function of the central nervous system. Evidence has shown previously that altered growth factor receptor signaling contributes to lesion formation, impedes recovery, and plays a role in disease progression. Growth arrest-specific protein 6 (Gas6), the ligand for the TAM receptor tyrosine kinase family, consisting of Tyro3, Axl, and Mer, is important for cell growth, survival, and clearance of debris. In this study, we show that levels of membrane-bound Mer (205 kd), soluble Mer ( approximately 150 kd), and soluble Axl (80 kd) were all significantly elevated in homogenates from established multiple sclerosis lesions comprised of both chronic active and chronic silent lesions. Whereas in normal tissue Gas6 positively correlated with soluble Axl and Mer, there was a negative correlation between Gas6 and soluble Axl and Mer in established multiple sclerosis lesions. In addition, increased levels of soluble Axl and Mer were associated with increased levels of mature ADAM17, mature ADAM10, and Furin, proteins that are associated with Axl and Mer solubilization. Soluble Axl and Mer are both known to act as decoy receptors and block Gas6 binding to membrane-bound receptors. These data suggest that in multiple sclerosis lesions, dysregulation of protective Gas6 receptor signaling may prolong lesion activity.

Differential expression, and genetic association, of CD58 in Swedish multiple sclerosis patients

We report additional genetic and transcriptomic evidence for the role of CD58 (LFA-3) in multiple sclerosis (MS) susceptibility using a Swedish case-control material, with a result that closely mimics that of De Jager et al. (1). This gene was originally selected for further assessment because of implications in MS susceptibility (2), and because of reduced expression in the cerebrospinal fluid (CSF) of MS patients compared to controls investigated using the Affymetrix Human Genome U133 plus 2 arrays, where 2 probe sets for CD58 detected fold changes of 0.65–0.8 (P = 3.1 × 10−3 and 4.4 × 10−2). The current study included 1,077 patients and 1,217 blood-donor controls, all residing in the Stockholm area and of Scandinavian ancestry. Markers from HapMap Phase II were selected to capture most variance around CD58, and Sequenom methodology was utilized to assess genotypes at 12 SNPs. Association was tested by using logistic regression in R, validating the association of several CD58 SNPs. Most notably, the strongest effect was seen by the correlated (r2 of 0.52) alleles rs10924103G and rs12044852A, in analogy with previous results (1), showing odds ratios of 0.73 and 0.72 in multiplicative models (P = 8.3 × 10−5 and 4.3 × 10−4) and an etiological fraction of 45%. Thus, we are able to contribute to the knowledge of CD58 in MS by, in a Swedish material, reporting lowered expression of this costimulatory molecule in the CSF of MS patients, and confirming the genetic association.

MRI criteria in MS patients with negative and positive oligoclonal bands: equal fulfillment of Barkhof’s criteria but different lesion patterns

In multiple sclerosis (MS) more than 95% of the patients have positive oligoclonal bands (OCB) in the cerebrospinal fluid (CSF). Previous studies have reported differences between patients with and without OCB mainly with regard to clinical parameters such as age, gender, disease duration, and clinical severity. However, several MRI characteristics have also been hypothesized to be distinct, and a varying lesion load in OCB-negative and -positive patients is proposed. In this study, we aimed to evaluate whether Barkhof's diagnostic MRI criteria are unequally frequently fulfilled in OCB-negative and -positive MS patients. We screened our database for all OCB-negative MS patients who had (1) been treated with the diagnosis of a clinical definite relapsing-remitting MS in our institution as well as (2) undergone CSF analysis and MR brain imaging during hospital stay between January 2004 and December 2007. Eleven OCB-negative patients were identified who fulfilled these criteria. In a second step, we carefully matched each of them to two OCB-positive controls according to age, gender, EDSS, and disease duration. The separate analysis of the several parameters of Barkhof's criteria revealed a less frequent prevalence of infratentorial (3/11 vs. 18/22; P = 0.005) and a more frequent occurrence of juxtacortical lesions (10/11 vs. 10/22; P = 0.022) in OCB-negative as compared to OCB-positive patients. The overall fulfillment of the Barkhof criteria did not differ in OCB-negative and -positive patients (7/11 vs. 16/22; P = 0.696). Further analyses of MRI findings between OCB-negative and -positive MS patients might contribute to a better pathophysiological understanding of the genesis and evidence of OCB in the CSF of MS patients.

Increased Soluble TREM-2 in Cerebrospinal Fluid from Patients with Multiple Sclerosis and CNS Inflammation

Evaluation of: Piccio L, Buonsanti C, Cella M et al.: Identification of soluble TREM-2 in the cerebrospinal fluid and its association with multiple sclerosis and CNS inflammation. Brain 131, 3081–3091 (2008). TREM-2 is a membrane-bound receptor expressed by microglia and macrophages and its engagement reduces inflammation. In this study, a soluble form of TREM-2 (sTREM-2) is identified. Cerebrospinal fluid (CSF) sTREM-2 levels were found to be higher in relapsing–remitting multiple sclerosis patients (n = 52) compared with noninflammatory neurologic diseases cases (n = 41; p = 0.004). Primary-progressive multiple sclerosis patients (n = 21) and other inflammatory neurologic diseases subjects (n = 19) also had high CSF TREM-2 levels (p < 0.001). Furthermore, a subset of CSF monocytes expressed TREM-2, which was also highly expressed on myelin-laden macrophages in active demyelinating lesions. The elevated levels of sTREM-2 in the CSF of multiple sclerosis patients may inhibit the anti-inflammatory function of the membrane-bound receptor. Therefore, sTREM-2 may be a possible target for future therapies.

Autoantibodies to myelin basic protein are not present in the serum and CSF of MS patients.

Myelin basic protein (MBP) is one of the main constituents of the CNS myelin sheaths, and an autoimmune response directed against MBP may be crucial in the demyelination process in patients with multiple sclerosis (MS). In this study sera and cerebrospinal fluid (CSF) from 25 MS patients, 25 patients with other neurological diseases and 16 healthy controls were examined for antibodies against MBP by using radio immunoblot, western blot, radio immunoassay and enzyme-linked immunosorbent assay. No evidence for the presence of antibodies to MBP was found in sera or CSFs in either the MS patients, or in the control groups tested.

Immunoreactive leukotriene C4 levels in CSF of MS patients.

Using a sensitive and specific radioimmunoassay levels of leukotriene (LT)C4-like material were estimated in lumbar cerebrospinal fluid (CSF) samples from patients with multiple sclerosis (MS) in comparison to control patients with or without inflammatory processes in the central nervous system (CNS). Levels of LTC4-like material were significantly elevated (p less than 0.01) in CSF from patients with inflammatory diseases such as meningitis, polyradiculitis or meningoencephalitis (57 +/- 53 pg/ml, n = 16) as compared to those from control patients without inflammatory or immunological CNS diseases (21 +/- 16 pg/ml, n = 42). By contrast, LTC4-like material was 16 +/- 7 pg/ml in first manifestations of MS (n = 7). 21 +/- 16 pg/ml in remitting-relapsing MS (n = 15) and 10 +/- 6 pg/ml in chronic progressive MS (n = 8). These results argue against a significant pathophysiological role of cysteinyl-LT in MS.

Immune complexes in serum and cerebrospinal fluid of multiple sclerosis patients and patients with other neurological diseases.

Paired serum and cerebrospinal fluid (CSF) specimens from 30 multiple sclerosis (MS) patients and 30 patients with other neurological diseases (ONDs) were analyzed for the presence of immune complexes (ICs). With each of the 4 tests used, ICs were found more frequently in sera from both MS and OND patients than in sera from healthy blood donors. IC-positivity for MS and OND patient CSF varied from 10-33% and from 10-17% in different tests. The number of IC-positive sera or CSF in MS patients did not differ significantly from those in OND patients. For both MS and OND patients, the positivity pattern for serum and CSF specimens in each IC test was essentially unique. Furthermore, because several CSF IC-positive and serum IC-negative paired specimens were found, intrathecal IC formation may be independent of IC formation in peripheral blood. The presence of ICs in serum or CSF did not correlate with the clinical status of or laboratory data on the MS patients, nor was a correlation found with the diagnosis of the OND patients. In total, these results suggest that the presence or absence of ICs in MS or OND patients may simply reflect changes in the immunological regulation of individual patients.

CORRELATION OF THE IGG INDEX AND OLIGOCLONAL BANDS IN THE CEREBROSPINAL FLUID OF PATIENTS WITH MULTIPLE SCLEROSIS

The aim of this study was to assess the correlation between IgG index values and the number of the oligoclonal IgG bands (OCB) in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS). The set of 150 patients consisted of 41 males and 109 females (aged 18-68, mean 36.6 +/- 10.1 years). The CSF collected by a lumbar puncture was examined evaluating intrathecal synthesis using the IgG index and determining OCB. The number of alkaline OCB in the CSF was assessed using the method of isoelectric focusing. Pearson's correlation analysis, and homogeneity chi(2) test, Mann-Whitney test, paired-sample t-test (parametric) and Wilcoxon signed-ranks test (nonparametric) were used to evaluate the statistical significance of the results. No positive correlation between the IgG index and the number of OCB was found. Mann-Whitney test also failed to demonstrate any significant difference of the IgG index values in patients both with the OCB number > or = 2 and < 2. This study did not confirm any correlation between the IgG index values and the OCB number in the CSF of MS patients.

Platelet-Activating Factor Production in the Spinal Cord of Experimental Allergic Encephalomyelitis Mice via the Group IVA Cytosolic Phospholipase A2-Lyso-PAFAT Axis

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) plays a critical role in inflammatory disorders including experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). Although PAF accumulation in the spinal cord (SC) of EAE mice and cerebrospinal fluid of MS patients has been reported, little is known about the metabolic processing of PAF in these diseases. In this study, we demonstrate that the activities of phospholipase A(2) (PLA(2)) and acetyl-CoA:lyso-PAF acetyltransferase (LysoPAFAT) are elevated in the SC of EAE mice on a C57BL/6 genetic background compared with those of naive mice and correlate with disease severity. Correspondingly, levels of groups IVA, IVB, and IVF cytosolic PLA(2)s, group V secretory PLA(2), and LysoPAFAT transcripts are up-regulated in the SC of EAE mice. PAF acetylhydrolase activity is unchanged during the disease course. In addition, we show that LysoPAFAT mRNA and protein are predominantly expressed in microglia. Considering the substrate specificity and involvement of PAF production, group IVA cytosolic PLA(2) is likely to be responsible for the increased PLA(2) activity. These data suggest that PAF accumulation in the SC of EAE mice is profoundly dependent on the group IVA cytosolic PLA(2)/LysoPAFAT axis present in the infiltrating macrophages and activated microglia.

Cover Picture: Clonally expanded plasma cells in the cerebrospinal fluid of MS patients produce myelin‐specific antibodies – Eur. J. Immunol. 7/2008

AbstractThe cover shows a confocal micrograph of myelinated nervous tissue at the rim of a demyelinating lesion in the brain white matter of a patient with multiple sclerosis (MS). Myelin surrounding the axon is stained by a monoclonal antibody obtained by recombinant expression of immunoglobulin genes from clonally expanded plasma cells as present in the cerebrospinal fluid of MS patients. The image was taken from the article by von Büdingen et al. (pp.2014–2023) in which the authors demonstrate that myelin specific antibodies result from antigen driven immune responses found in the cerebrospinal fluid of MS patients.

In this issue

In this issue

Clonally expanded plasma cells in the cerebrospinal fluid of MS patients produce myelin‐specific antibodies

Clonally expanded plasma cells (cePC) and their presumed products, oligoclonal immunoglobulin G bands (OCB), are characteristic findings in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS). While cePC and OCB strongly suggest an involvement of B cell-dependent immune mechanisms in the pathogenesis of MS, their actual pathological relevance and target antigens remain unknown. To further understand the potential role played by cePC, we generated a panel of monoclonal antibodies (MS-mAb) from CSF-derived cePC from four patients with early or definite MS. Single-cell RT-PCR of correctly paired heavy and light chain immunoglobulin genes from individual cePC ensured the subsequent resurrection of their original antigen specificity. Immunofluorescence stainings of MS lesion tissue with MS-mAb revealed myelin reactivity in the cePC repertoire of all four patients and intracellular filament reactivity in one patient. While myelin staining by MS-mAb was only rarely detectable in non-MS CNS white matter tissue, it was greatly enhanced at the edge of demyelinating lesions in MS brain tissue. Our findings provide conclusive evidence for the presence of an antigen-driven B cell response in the CSF of MS patients directed against epitopes present in areas of myelin degradation.

Herpesviruses and human endogenous retroviral sequences in the cerebrospinal fluid of multiple sclerosis patients

Objective To analyze the possible role of human herpesvirus (HHVs) and human endogenous retroviruses (HERVs) infection in multiple sclerosis (MS) pathogenesis. Methods A total of 92 cerebrospinal fluid (CSF) samples were collected: 48 from MS patients at the first clinically evident demyelinating event, 23 from patients with other inflammatory neurological diseases (OINDs) and 21 from patients with other non-inflammatory neurological diseases (ONINDs). Total DNA and RNA were isolated, and the prevalences and viral loads of herpes simplex virus (HSV), varicella-zoster virus (VZV), Epstein–Barr virus (EBV), cytomegalovirus (CMV), HHV-6, HERV-H and HERV-W in the CSF of MS patients and controls were evaluated using a quantitative real-time polymerase chain reaction assay. Results (i) For HSV, 1/48 (2.1%, 86 copies/ml of CSF) MS patients and 1/23 (4.3%, 115.2 copies/ml of CSF) OIND patients (a myelitis case) had HSV sequences in the CSF; (ii) for EBV, only 1/48 (2.1%, 72 copies/ml of CSF) MS patients was positive for EBV; (iii) for HHV-6, only 5/48 (10.4%) MS patients had HHV-6 genomes in their CSF (128.1 copies/ml of CSF); (iv) we did not find any positive cases for VZV, CMV, HERV-H and HERV-W among MS patients or controls; (v) no cases of co-infections were found; (vi) the whole prevalence of HHVs was 7/48 (14.6%) for MS patients and 1/44 (2.3%) for controls (p = 0.038). Conclusion The findings described here show that HHV infection is more frequent in the CSF of MS patients than in patients with other neurological diseases; however, only HHV-6 seems to be involved in the pathogenesis of MS in a subset of patients.

Significantly increased antibody response to heterogeneous nuclear ribonucleoproteins in cerebrospinal fluid of multiple sclerosis patients but not in patients with human T-lymphotropic virus type I–associated myelopathy/tropical spastic paraparesis

It has been reported that antibodies (Abs) against heterogeneous nuclear ribonucleoproteins (hnRNPs) are associated with human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and multiple sclerosis (MS). However, these studies were done under nonmasked conditions. In order to determine whether Abs against hnRNPs associate with HAM/TSP and MS, the authors assayed Abs against two major hnRNPs, hnRNP A1 and A2/B1, in 105 cerebrospinal fluid (CSF) samples under fully masked conditions. Samples included 40 cases of HAM/TSP, 28 of MS, and 37 of other neurological diseases. Anti-hnRNP A1 Abs, and especially anti-hnRNP A2/B1 Abs, were found significantly more often in the CSF of MS patients than in other groups. However, there was no difference in the incidence of anti-hnRNP A1 Abs between HAM/TSP and other disease groups.

Reply to letter to the editor: "JC viremia and multiple sclerosis" by Focosi et al.

First of all, we would like to thank the authors for the interest and the opportunity to go into depth of our results concerning the possible role of beta interferon treatment on frequency of JC virus (JCV) DNA detection in peripheral blood mononuclear cells (PBMCs) of multiple sclerosis (MS) patients. The authors are concerned because in their opinion DNA of JCV could not be found also in the peripheral blood of healthy people and, to this regard, they quote several scientific papers reporting negative results. However, the analysis of the literature performed by them is restricted because it ignores a large body of evidences reported by several authors, in more recent years, and showing the presence at a variable range of JCV DNA in the peripheral blood of both healthy subjects and patients with MS (Dorries et al, 1994, 2003; Azzi et al, 1996; Gu et al, 2003; Pietropaolo et al, 2005). At the end of the paragraph regarding this topic, the authors suspect that polymerase chain reaction (PCR) we used could be flawed by methodological errors. The only possible answer to these comments is that our experience in the field of JCV dates from a long time and, more important, we participated to the recently settled European Quality Control for JCV/BKV PCR methods validation with excellent results (www.qcmd.org, 2007). The authors also hypothesize that the presence of JCV in PBMCs of relapsing-remitting MS (RRMS) patients could be due to a misdiagnosis of progressive multifocal leukoencephalopathy (PML). We underline again that our MS patients were diagnosed according to the Poser et al (1983) criteria. Moreover, we believe that only inexpert neurologists could confuse PML with MS, mostly if we consider that our patients had MS diagnosed many years before the samples’ collection. We would also like to inform the authors and to highlight that the first scientist suggesting a possible etiological relation between MS and JCV was the late lamented Gerald Stoner (1991). On these themes Focosi and colleagues recall also that Du Pasquier et al showed a strong cytotoxic lymphocyte (CTL) response against JCV VP1 in MS patients (Du Pasquier et al, 2006). In our opinion, this is an indirect evidence of the fact that JCV circulates in the blood of MS patients, stimulating immune competent cells against viral antigens. Regarding our previous data (Ferrante et al, 1998) showing the presence of JCV DNA in cerebrospinal fluid (CSF), Focosi et al stated that other authors did not confirm this report. Recently, we confirmed these results (Mancuso et al, 2007) and we would like to point out again that MS is a disease that can last for more than 20 years and its diagnosis is usually made from 5 to 15 years after the real onset of the disease. In addition, MS is characterized by very high cellular trafficking from periphery to central nervous system (CNS), an aspect that, in our opinion, supports the transport of viruses, and not only JCV, to the CNS and to the CSF of MS patients. We could also speculate about the preanalytical phase of the study of viruses’ research in CSF (time of collection, length and methods of storage, etc.), but due to space restriction, we will not discuss this issue further. Again regarding the possible relation between JCV and MS, Focosi et al quoted, without any apparent reason, the paper of Agostini et al (2000), showing the high frequency of JCV genotype 2b in PML patients, a finding that was also shown by our group (Ferrante et al, 2001). Finally the authors underlined the differences between our data and those by Alvarez-Lafuente et al (2007) who did not find any statistically significant differences between treated and untreated MS patients. We would like to suggest that not only methodological aspects could be different but also the geographical provenience, clinical history, and perhaps genetic background of our patients and Alvarez-Lafuente’s patients could be different. However, this is only the beginning of a new era of interest in JCV and MS relationship and we believe that we must be open to different possible results during the coming years each time a new aspect of a very complex disease, such as MS, is studied.

Astrocytic activation in relation to inflammatory markers during clinical exacerbation of relapsing-remitting multiple sclerosis

The study aimed to assay the cerebrospinal fluid (CSF) levels of protein S100B, a biomarker of astrocyte activation in relation to kynurenic acid (KYNA) and nitric oxide (NO) metabolites, nitrate/nitrite (NOx) concentrations in acute relapse multiple sclerosis (MS) patients. Twenty relapsing-remitting MS (RR-MS) patients and 10 controls were enrolled. RR-MS patients were assessed on the expanded disability status scale (EDSS) and underwent lumbar puncture. The CSF KYNA, NOx and S100B levels were significantly higher in RR-MS group compared to controls (p = 0.01, 0.001, 0.04, respectively). There was a significant correlation between CSF S100B and KYNA (p = 0.01) but not NOx (p > 0.05) in RR-MS. CSF KYNA, NOx or S100B concentrations did not correlate with disease characteristics of MS patients. Our study suggests the activation of the kynurenine pathway leading to the increase of neuroprotective KYNA in the CSF of MS patients during acute relapse what contrasts with chronic phases of the disease.

Potential Role of Humoral Immunity in the Pathogenesis of Multiple Sclerosis (MS) and Experimental Autoimmune Encephalomyelitis (EAE)

The earliest research literature addressing sub-clinical characteristics of Multiple Sclerosis was largely focused on humoral immune components, particularly antibodies in the cerebrospinal fluid of MS patients. However, two decades later, in the 1990's, T cells were established as a major component of the underlying mechanism(s) of MS pathogenesis, especially since EAE, the mouse model of MS, could be readily induced by immunization with myelin derived peptides or passive transfer of encephalogenic T cells. This data has contributed to the concept that the role of humoral immunity in MS pathogenesis may be negligible. However, more recent studies have provided important insights regarding the role of humoral immunity in MS pathogenesis. The goals of this review are to 1) summarize evidence for and against the hypothesis that humoral immunity plays a central role in the pathogenesis of MS, and 2) summarize studies in the EAE model that directly tested the role of humoral immunity in pathogenesis of the disease. With this information, we hope to convince the reader that great strides have been made towards defining a central role of humoral immunity in MS pathogenesis, but that there is a substantial amount of work to be done (especially in the EAE model) to ensure that the contribution of humoral immunity to MS pathogenesis is effectively addressed.

Anti-heat shock protein 90β antibodies are detected in patients with multiple sclerosis during remission

Antibodies against heat shock protein 90β (Hsp90β) recognize the antigen on the surface of oligodendrocyte precursor cells and induce a decrease in the oligodendrocyte population of cell cultures. This study investigated the presence of anti-Hsp90β antibodies in patients with multiple sclerosis (MS) during remission. Anti-Hsp90β antibodies were detected in the cerebrospinal fluid (CSF) of patients with a specific and sensitive western blot procedure using Hsp90β from cell membrane fraction. The number of patients with anti-Hsp90β antibodies detected in the CSF was significantly greater in MS patients than in control patients with other neurological diseases, which included patients with other inflammatory neurological diseases. CSF anti-Hsp90β antibody levels were significantly higher in MS patients than in control patients. The presence of anti-Hsp90β antibodies in the CSF of MS patients during remission could suggest a potential pathogenic role for these autoantibodies in MS.

Increase of CD8+ T-effector memory cells in peripheral blood of patients with relapsing–remitting multiple sclerosis compared to healthy controls

CCR7 and CD45RA expression on CD4+ and CD8+ T-cells in blood (PB) of 16 patients with multiple sclerosis (MS) and 16 healthy controls and cerebrospinal fluid (CSF) of 10 patients suffering from MS were analysed by flow cytometric measurements. T-cells were divided by their distinct homing potentials and effector-functions in three groups: naïve T-cells (CCR7+, CD45RA+), central memory T-cells (T CM) (CCR7+, CD45RA−) and effector memory T-cells (T EM) (CCR7−, CD45RA−). There was a significant increase of CD8+ T EM-cells in PB of MS patients compared to healthy controls, indicating systemic immune activation. Further we found a relative depletion of CD8+ T EM-cells in CSF of MS patients compared to matching blood samples, suggesting that these cells represent the effector arm of the immune response and infiltrate the brain tissue at the sites of inflammation.