Increased T cell expression of CD154 (CD40-ligand) in multiple sclerosis

CD154 (CD40-ligand, gp39), expressed on activated T cells, is crucial in T cell-dependent immune responses and may be involved in the pathogenesis of multiple sclerosis (MS). We studied cerebro-spinal fluid and peripheral blood T cell expression of CD154 in MS by flow cytometry. Patients with secondary progressive MS (SPMS) had constitutive CD154 expression on CD4 and CD8 T cells in blood. Constitutive CD154 expression was not observed in patients with relapsing-remitting MS (RRMS) or clinically isolated syndromes (CIS) suggestive of demyelinating disease. After ex vivo activation CD154 was, however, expressed on a higher percentage of T cells from patients with CIS or RRMS than from healthy control subjects. These results suggest involvement of CD154 in the pathogenesis of MS, and the shift from a relapsing-remitting to a secondary progressive disease course may be associated with constitutive, systemic CD154 expression.     

Dysregulation of IL-10 and IL-12p40 in secondary progressive multiple sclerosis

Multiple sclerosis (MS) is a putative T helper 1 (Th-1) mediated inflammatory disorder of the central nervous system, and levels of pro-inflammatory and anti-inflammatory cytokines have been found to correlate with changes in MS relapses. However, it is unclear if cytokine profiles differ between relapsing-remitting (RRMS) versus secondary progressive (SPMS) disease stages. Cytokine production (IL-2, IL-4, IL-5, IL-10, IL-12p40, TNF-alpha, and IFN-gamma) was assessed by cytometric bead array (CBA) and intracellular cytokine staining from alphaCD3 antibody and mitogen stimulated peripheral blood mononuclear cells (PBMCs) from female RRMS and SPMS patients, and healthy controls. Significantly increased production of IL-12p40 and decreased production of IL-10 were observed in SPMS patients. Differences in immune responsiveness in RRMS and SPMS are important in the understanding of the evolution of the immunopathogenesis of the disease and for the development of disease type specific treatments.     

Defective regulation of IFNgamma and IL-12 by endogenous IL-10 in progressive MS

BACKGROUND: MS is a chronic inflammatory disease of the CNS postulated to be a Th1 type cell-mediated autoimmune disease. There is increased interferon-gamma (IFNgamma) secretion in MS, and IFNgamma administration induces exacerbations of disease. IFNgamma expression is closely regulated by a number of cytokines produced by different cells of the immune system. Interleukin-12 (IL-12) is a major factor leading to Th1-type responses, including IFNgamma secretion, and there is increased secretion of IL-12 in MS. IL-10 is a potent inhibitor of both IL-12 and IFNgamma expression. METHODS: The authors investigated cytokine production and proliferative responses of peripheral blood mononuclear cells stimulated with soluble anti-CD3 in healthy controls and patients with stable relapsing-remitting MS or progressive MS. RESULTS: The authors found that T cell receptor-mediated IFNgamma and IL-10 secretion were increased in progressive MS, whereas IL-4 and IL-2 secretion and lymphocyte proliferative responses were normal. Anti-IL-12 antibody suppressed raised IFNgamma in progressive MS but did not affect raised IL-10. In addition, neutralization of endogenous IL-10 upregulated IFNgamma in controls but not progressive MS. IL-10 was produced by CD4+ cells whereas IFNgamma was produced by both CD4+ and CD8+ cells. There were no differences in IL-10 receptor expression in MS patients. CONCLUSIONS: These abnormalities in IL-10 regulation were not seen in the relapsing-remitting form of MS. Thus, the defect in regulation of both IL-12 and IFNgamma production by endogenous IL-10 in progressive MS could be an important factor involved in the transition of MS from the relapsing to the progressive stage and has implications for treating MS patients with exogenous IL-10.     

Blockade of CD40/CD40 ligand interactions prevents induction of factor VIII inhibitors in hemophilic mice but does not induce lasting immune tolerance.

Patients with severe hemophilia A frequently develop neutralizing anti-factor VIII antibodies after replacement therapy with factor VIII (FVIII). In a search for new strategies to induce immune tolerance against FVIII in these patients, we used a murine model of hemophilia A to investigate the importance of CD40/CD40 ligand (CD40L) interactions for the initiation of the anti-FVIII immune response. We focused our attention in particular on the induction of neutralizing anti-FVIII antibodies and the Th1/Th2 polarization of FVIII-specific T cells. The development of anti-FVIII antibodies was analyzed by ELISA systems (detection of total anti-FVIII antibodies) and Bethesda assays (determination of neutralizing anti-FVIII antibodies). Factor VIII-specific T cells were characterized by multiparameter flow cytometry and cytokine ELISAs for the detection of cytokine production in splenic CD4+ T cells after in vitro restimulation with FVIII. Hemophilic mice received four doses of FVIII and anti-CD40L antibody MR1 (24 h before FVIII). Subsequently mice received four doses of FVIII only. The induction of neutralizing anti-FVIII antibodies in hemophilic mice after treatment with human FVIII could be prevented completely by a blockade of CD40/CD40L interactions using MR1. Furthermore, FVIII-specific T-cell responses that included both Th1 and Th2 cells were suppressed when mice were treated with FVIII and MR1. The initial blockade of CD40/CD40L interactions was, however, not sufficient to induce a lasting immune tolerance against FVIII. The immune suppression was abolished and both neutralizing anti-FVIII antibodies and FVIII-specific T cells developed when treatment with FVIII was continued after the omission of MR1. In addition, there were no alterations in the Th1/Th2 polarization induced by the initial blockade of CD40/CD40L interactions.     

Intracellular cytokine profile in T-cell subsets of multiple sclerosis patients: different features in primary progressive disease

OBJECTIVE: To evaluate the expression of cytokines in both CD4+ and CD8+ T cells derived from peripheral blood of untreated multiple sclerosis (MS) patients with either relapsing-remitting (RR), secondary progressive (SP) or primary progressive (PP) MS and healthy controls (HC). BACKGROUND: MS is an immune-mediated disease and cytokines hove been hypothesized to contribute significantly to disease progression. Compared to the relapse-onset (RR, SP) form of the disease, PPMS patients have different clinical, immunological and pathological features. Surprisingly, the ability of their circulating T cells to produce immunoregulatory cytokines has not been extensively studied so far. METHODS: Seventy-two MS patients (24 RR, 26 SP, 22 PP) and 34 HC were studied. Stimulated peripheral blood derived CD4+ and CD8+ T MS patients express significantly more CD4+ and CD8+ T cells were analyzed for IFN-gamma, IL-2, TNF-alpha, IL-4, IL-10 and IL-13 production. RESULTS: cells producing IFN-gamma compared to HC. Compared to the other forms of the disease, PPMS patients display a significant decrease in CD4+ T cells producing IL-2, IL-13 and TNF-alpha and a significant increase in CD8+ T cells producing IL-4 and IL-10. CONCLUSIONS: The data presented here demonstrate that patients with PPMS express less pro- and more anti-inflammatory cytokine producing T cells compared to the relapse-onset form of the disease, confirming the view on PPMS as a distinct disease entity.     

Anti-IL-16 therapy reduces CD4+ T-cell infiltration and improves paralysis and histopathology of relapsing EAE

Infiltration of the central nervous system (CNS) by CD4+ Th1 cells precedes onset and relapses of experimental autoimmune encephalomyelitis (EAE). We reported that (B6xSJL) F1 (H-2b/s) mice with severe relapsing-remitting disease had extensive infiltration by CD4+ T cells compared to that in C57BL/6 (B6) (H-2b) mice, which developed mild low-relapsing disease in response to myelin oligodendrocyte peptide 35-55 (MOG(35-55)). This observation led us to search for mechanisms that specifically regulate trafficking of CD4+ cells in relapsing H-2b/s mice. We show that the CD4+ cell chemoattractant cytokine interleukin (IL)-16 has an important role in regulation of relapsing EAE induced by MOG(35-55) in the (B6xSJL) F1 (H-2b/s) mice. We found production of IL-16 in the CNS of mice with EAE. IL-16 levels in the CNS correlated well with the extent of CD4+ T-cell and B-cell infiltration during acute and relapsing disease. Infiltrating CD4+ T cells, B cells, and to a lesser extent CD8+ T cells all contained IL-16 immunoreactivity. Treatment with neutralizing anti-IL-16 antibody successfully reversed paralysis and ameliorated relapsing disease. In treated mice, diminished infiltration by CD4+ T cells, less demyelination, and more sparing of axons was observed. Taken together, our results show an important role for IL-16 in regulation of relapsing EAE. We describe a novel therapeutic approach to specifically impede CD4+ T cell chemoattraction in EAE based on IL-16 neutralization. Our findings have high relevance for the development of new therapies for relapsing EAE and potentially MS.     

CD40 engagement stimulates IL-12 p70 production by human microglial cells: basis for Th1 polarization in the CNS

The APC-derived cytokine interleukin (IL)-12 polarizes CD4 T cells towards the pro-inflammatory Th1 phenotype and has been shown to be crucial for the development of EAE in rodents. In this study we demonstrate that production of IL-12 by human adult CNS-derived microglial cells can be triggered by cell contact with activated T cells. Microglial activation and IL-12 production can be blocked by anti-CD154 mAbs. IL-12 production could also be induced by direct engagement of CD40 on microglia using a CD40 agonist. IL-12 secretion by microglia is significantly reduced by TNF and IFN-gamma antagonists showing that the IL-12 production is subject to regulation by auto- and paracrine stimuli.     

Differentiated Th1 autoreactive effector cells can induce experimental autoimmune encephalomyelitis in the absence of IL-12 and CD40/CD40L interactions.

IL-12 plays a critical role in the priming of Th1 responses to bacterial/parasitic antigens and autoantigens. Several studies have demonstrated a dependency on CD40/CD40L interactions and IL-12 for maintenance of both antibacterial/parasitic and autoreactive Th1 cells in vivo. However, it is still unclear if fully differentiated Th1 effectors require continued stimulation by IL-12. We demonstrate that the proliferative response and IFN-gamma production by a fully differentiated T cell line specific for myelin oligodendrocyte glycoprotein are completely independent of IL-12 and CD40/CD40L interactions. The capacity of this line to adoptively transfer experimental autoimmune encephalomyelitis is also independent of IL-12 and CD40/CD40L. These results have important implications regarding the therapeutic usefulness of blockade of IL-12 or the CD40/CD40L pathway for treatment of autoimmune disease.     

Different patterns of activation markers expression and CD4+ T-cell responses to ex vivo stimulation in patients with clinically quiescent multiple sclerosis (MS)

Patients with relapsing-remitting (RR) and secondary progressive (SP) forms of multiple sclerosis (MS), although in long-term clinical remission, showed different patterns of increased expressions of the activation markers: CD69, CD40L, and both membrane/surface and cytoplasmic CTLA-4 (mCTLA-4 and cCTLA-4, respectively) in freshly isolated peripheral blood (PB) CD4+ T cells compared with controls. Also observed were dysregulated responses to ex vivo stimulation in both groups of MS patients accompanied by increased IFN-gamma synthesis. Our findings may suggest that the mechanisms leading to each clinical form of the disease may be heterogeneous.     

Anti-IL-12 antibody prevents the development and progression of multiple sclerosis-like relapsing--remitting demyelinating disease in NOD mice induced with myelin oligodendrocyte glycoprotein peptide

Treatment with monoclonal anti-IL-12 antibody injected on day 0, 7 and 10 after immunization with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 in NOD mice resulted in significant suppression of the development and the severity of the chronic relapsing-remitting experimental autoimmune encephalomyelitis (EAE) both clinically and histologically. The spleen cells from anti-IL-12 antibody treated mice displayed markedly inhibited MOG35-55 specific proliferation and IFN-gamma production. MOG35-55 specific antibody production was enhanced by anti-IL-12 antibody treatment. These results suggest that IL-12 is critically involved in the pathogenesis of MOG-induced EAE and that antibody to IL-12 could be an effective therapeutic agent in the clinical treatment of autoimmune demyelinating diseases such as multiple sclerosis (MS).     

Activation of microglial cells by the CD40 pathway: relevance to multiple sclerosis.

It is well known that microglial cells perform a key role in mediating inflammatory processes, which are associated with neurodegenerative diseases such as multiple sclerosis (MS). In this study, we report that CD40 expression on microglia is greatly enhanced by a low dose (10 U/ml) of IFN-gamma. We also find that ligation of microglial CD40 by CD40L triggers a significant production of TNF-alpha. Activation of microglia by ligation of CD40 in the presence of IFN-gamma results in cultured cortical neuronal injury, which is markedly attenuated by blockade of the CD40 pathway or neutralization of TNF-alpha. Finally, we find significant levels of IFN-gamma and TNF-alpha in the medium of co-cultured activated CD4+ T cells and microglial cells, showing that microglia can supply the CD40 receptor to activated CD4+ T cells and suggesting that this cellular interaction is a key event in MS pathophysiology.     

Monocyte-derived dendritic cells in multiple sclerosis: the effect of bacterial infection

We investigated whether monocyte-derived dendritic cells (MDDCs) generated in vitro from bacteria-infected MS patients modified autoreactive T cells activation patterns. T cell clones (TCCs) stimulated with MDDCs from infected MS patients responded with maximal proliferation, inducing IL-12, IL-17 and IFN-gamma secretion, at concentrations significantly lower than after incubation with MDDCs isolated from uninfected individuals and bacterial meningitis (BM) patients. Moreover, infected MDDCs promoted TCCs survival, and secreted more IL-12, IL-18, and IL-23. Finally, MDDCs from infected MS subjects showed higher expression of myeloid differentiation factor 88 (MyD88), as well as of HLA-DR, CD1a, CD80, CD86, CD273, CD40, CD83 and CCR7 when compared to MDDCs from uninfected MS individuals, and BM patients. Thus, activation of the innate immune system by microbial products in MS patients affects the generation MDDCs and their ability to modify autoreactive T cell activation patterns, which may be linked to MS relapse induction during bacterial infections.     

Impaired interleukin-12 production in multiple sclerosis patients.

Multiple Sclerosis (MS), a disease of the human central nervous system, is believed to be a T cell mediated autoimmune disorder with genetic and environmental influences. Interleukin-12 (IL-12), a proinflammatory cytokine produced primarily by antigen presenting cells is a potent inducer of interferon-gamma (IFN-gamma) and other Th1 cytokines that may play an important role in MS pathogenesis. We have investigated IL-12 production induced by the T cell independent pathway in untreated and IFN-beta treated MS patients, healthy individuals and other neurological disease (OND) patients in response to the human pathogen Staphylococcus aureus. We report that peripheral blood mononuclear cells (PBMC) from untreated MS patients produce normal amounts of the biologically active IL-12 p70 heterodimer but significantly less free IL-12 p40 heavy chain than PBMC from both healthy and disease controls when challenged in vitro with Staphylococcus aureus. Both mRNA expression of the inducible IL-12 p40 chain and protein levels were found to be reduced in untreated MS patients. No decrease in the production of the IL-12 p40 was seen in MS patients on IFN-beta therapy. The decreased production of IL-12 p40 heavy chain is not attributed to increased IL-10 secretion, a defect in the production of cytokines by macrophages or the number of cytokine producing cells. The factor(s) responsible for the decrease in p40 remain to be determined. Since IL-12 p40 antagonizes the biological activity of IL-12 in vitro and in vivo, identification of a defect in the 'natural' antagonist of IL-12, may provide the basis for immune therapy.     

IL-18 in patients with multiple sclerosis

IL-18 is a cytokine which plays an important role in Th-1 response through its ability to induce IFN-gamma production in T cells and NK cells. The purpose of the study was to measure IL-18 levels in serum and CSF of 21 patients with the relapsing-remitting form of MS, 9 with active gadolinium enhancing lesions in MRI and 12 without enhancing lesions, and to compare results with control group consisting of 11 patients with diagnosis of neurasthenia and tension headache. IL-18 concentration in the CSF and sera was measured by ELISA. We found a highly significant increase of both IL-18 CSF and serum levels in MS patients in comparison with the control group. In patients with active MRI lesions the levels of IL-18 in CSF and serum were significantly higher in comparison with the levels found in patients without enhancing lesions. The results suggest involvement of IL-18 in immunopathogenesis of MS especially in the active stages of the disease.     

Multiple sclerosis: expression of CD1a and production of IL-12p70 and IFN-gamma by blood mononuclear cells in patients on combination therapy with IFN-beta and glatiramer acetate compared to monotherapy with IFN-beta

Current therapy of multiple sclerosis (MS) with interferon-beta (IFN-beta) or glatiramer acetate (GA) has modest effects on the course of MS. Both compounds affect several immune variables, like expression of cell surface molecules and cytokine levels. Here we compared untreated MS, therapy with IFN-beta alone and combined with GA, and healthy controls (HC), regarding expression on HLA-DR+ blood mononuclear cells (MNC) of CD1a that is a cell surface molecule with capacity to present glycolipids to T cells, and of CD80 and CD86 which are costimulatory molecules that activate Th1 and Th2 responses. Cytokine production by MNC was also measured. Flow cytometry and ELISA were used. Cross-sectional comparisons revealed that untreated MS patients had higher CD1a+ HLA-DR+ MNC and lower IL-10 production compared to patients treated with IFN-beta or IFN-beta+GA or HC. Untreated MS patients also had higher spontaneous IFN-gamma and IL-12p70 production compared to MS patients treated with IFN-beta+GA or HC, but not when compared to MS patients on monotherapy with IFN-beta. Low CD1a+ HLA-DR+ MNC and low spontaneous production of IL-12p70 and IFN-gamma were more pronounced in patients treated with IFN-beta+GA than with IFN-beta alone. In order to clarify whether these changes reflect disease activity or treatment effects, we performed a follow up study. Nineteen MS patients with disease progression, despite monotherapy with IFN-beta for more than one year; were re-examined after one to three and four to six months of treatment with IFN-beta+GA. This combination therapy was associated with normalization of CD1a+ HLA-DR+ MNC, IL-12p70 and IFN-gamma. It remains to be shown whether these immunological changes imply a clinical benefit. Follow up studies of immune variables versus clinical effects during combined therapy of MS with IFN-beta+GA are ongoing.     

Monocyte-derived HLA-G acts as a strong inhibitor of autologous CD4 T cell activation and is upregulated by interferon-beta in vitro and in vivo: rationale for the therapy of multiple sclerosis

Peripheral antigen presenting cells (APCs) contribute to the maintenance of immune tolerance and are considered to play a critical role in promoting the (re)activation of autoreactive T cells in multiple sclerosis (MS). Interferon-beta (IFN-beta) is the principle immune-modulatory agent used in the treatment of MS, but its mechanism of action remains elusive. HLA-G is a non-classical MHC molecule (MHC class Ib) attributed chiefly immune-regulatory functions. We here investigated the role of monocyte-derived HLA-G in the immune-regulatory processes of MS and its implications for current immune-modulatory therapies. Monocytes constitutively express cell surface HLA-G1 and soluble HLA-G5. Comparison of monocytic HLA-G expression between patients with relapsing-remitting MS (n=17) and healthy donors (n=20) revealed significantly lower levels of HLA-G1 protein in MS patients. However, both groups showed a significant upregulation of HLA-G in response to IFN-beta in vitro. Serial measurements of HLA-G mRNA levels in MS patients before and during IFN-beta therapy corroborated the relevance of these results in vivo: 1 month after initiation of IFN-beta1b therapy (n=9), HLA-G1 and HLA-G5 were significantly increased compared to baseline levels and remained elevated during treatment for 6 months (n=3). Importantly, functional experiments demonstrated that monocyte-derived HLA-G inhibits both Th1 (IFN-gamma, IL-2) and Th2 (IL-10) cytokine production by antigen-stimulated autologous CD4 T cells. Soluble HLA-G added to antigen-specific T cell lines (TCLs) has similar effects on the release of cytokines and reduces T cell proliferation. Although both IFN-beta and IFN-gamma strongly enhance HLA-G1 and HLA-G5 expression by monocytes in vitro, IFN-beta leads to a stronger relative upregulation of HLA-G compared to classical MHC class I molecules than stimulation with IFN-gamma. Taken together, monocyte-derived HLA-G mediates the inhibition of autologous CD4 T cell activation and might be involved in immune-regulatory pathways in the pathogenesis of MS. We conclude that some desirable immune-modulatory effects of INF-beta might be accomplished via the upregulation of the immune-tolerogenic molecule HLA-G.     

Decreased interleukin-10 and increased interleukin-12p40 mRNA are associated with disease activity and characterize different disease stages in multiple sclerosis.

It has been shown that proinflammatory and antiinflammatory cytokines correlate with disease activity in multiple sclerosis (MS). To establish whether such correlations depend on the disease stage, we assessed in a longitudinal fashion the expression of interleukin (IL)-12 (p40 and p35), tumor necrosis factor-alpha, interferon-gamma, and IL-10 mRNA by competitive polymerase chain reaction in unstimulated peripheral blood mononuclear cells of relapsing-remitting (RR) and secondary progressive (SP) MS patients, in relation to monthly clinical and magnetic resonance imaging monitoring. MS patients had increased levels of IL-12p40 and decreased levels of IL-10 mRNA compared with controls; this difference was most pronounced in SP patients. Both RR and SP patients had increased levels of IL-12p40 mRNA compared with controls during the development of active lesions. Moreover, in RR MS an increase was found before relapse. IL-12p35 mRNA was decreased in both groups, and in relation to disease activity it showed a pattern different from IL-12p40 mRNA. In RR MS, IL-10 mRNA was low 4 weeks before magnetic resonance imaging activity and 6 weeks before relapse; a significant increase to normal levels was noted when active lesions became apparent. In contrast, SP patients showed low IL-10 mRNA levels constitutively, suggesting that IL-10 plays an important role in the control of disease progression.     

Cyclophosphamide modulates CD4+ T cells into a T helper type 2 phenotype and reverses increased IFN-gamma production of CD8+ T cells in secondary progressive multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system considered to be mediated by T helper type-1 cells. Several agents have been found to modify the disease course of MS, including interferon-beta1 (IFN-beta1), glatiramer acetate mitoxantrone. We have employed pulse therapy with cyclophosphamide in a selected group of patients with actively progressive disease. Chemokine receptors have been found to differentiate between polarized T helper type-1 (Th1) and type-2 (Th2) lymphocytes. The chemokine receptors CCR5 and CXCR3 are expressed primarily on Th1 cells and CCR3, CCR4 and CCR8 on Th2 cells. Previous studies of the expression of chemokine receptors in MS have shown that active MS plaques are infiltrated by CCR5(+) and CXCR3(+) T cells. Some of these T cells may express both CCR5 and CXCR3. These T cells are major producers of IFN-gamma, which worsens the clinical condition of patients with MS. We previously found that patients with MS had a high proportion of CXCR3(+) T cells and that those with chronic progressive MS had a high proportion of CCR5(+) T cells in their peripheral blood. We report here that in patients with secondary progressive MS, cyclophosphamide induces a marked increase in the percentage of CCR4(+) T cells that produce high levels of IL-4 and reverses the increase in the percentages of IFN-gamma-producing CCR5(+) and CXCR3(+) CD8(+) T cells. Furthermore, therapy with cyclophosphamide increases IL-4-producing CD4(+) T cells and reverses the increase in IFN-gamma-producing CD8(+) T cells. Our study shows that cyclophosphamide has immunomodulatory properties besides its suppressive effects, and that chemokine receptors can be important tools both for understanding the immune dysregulation in MS and for monitoring response to therapy.     

Interferon-beta regulates cytokines and BDNF: greater effect in relapsing than in progressive multiple sclerosis

The mechanism of action of interferon (IFN)-beta therapy in multiple sclerosis (MS) is only partially known, and its efficacy changes with disease stage. In different forms of MS, we determined how IFN-beta regulates mononuclear cell production of the important anti-inflammatory Th2 cytokine - IL-10, the Th1 cytokine - IFN-gamma, and the brain-derived neurotrophic protein - BDNF. Activated T cells and monocytes from therapy-na?ve patients secreted more IL-10 than healthy controls. During IFN-beta therapy, however, T cells produced less IL-10. In vitro, IFN-beta stimulated IL-10 production by activated T cells, but inhibited IL-10 secretion by activated monocytes, a richer source of IL-10 than T cells. The form of MS also affected cytokine production. IL-10 and BDNF levels in MNC were high during relapsing/remitting (RR) MS, but low in progressive MS. Surprisingly, IFN-beta therapy increased BDNF levels in antidepressant-na?ve patients, but BDNF was lower during concurrent antidepressant drug therapy, suggesting an interaction between MS, depression, and neurodegeneration. IFN-beta in vitro strongly induced IL-10 and IFN-gamma in activated T cells in RRMS, but not in progressive MS, suggesting IFN resistance. IFN-beta effects are specific for disease state and immune subsets, possibly explaining why IFN-beta therapy is most effective in early T cell-regulated RRMS, but less beneficial in progressive MS, where chronic plaques contain few T cells and high numbers of monocytes.