Genetic variation near IRF8 is associated with serologic and cytokine profiles in systemic lupus erythematosus and multiple sclerosis.

Alleles of interferon (IFN) regulatory factor 8 (IRF8) are associated with susceptibility to both systemic lupus erythematosus (SLE) and multiple sclerosis (MS). Although high-type I IFN is thought to be causal in SLE, type I IFN is used as a therapy in MS. We investigated whether IRF8 alleles were associated with type I IFN levels or serologic profiles in SLE and MS. Alleles that have been previously associated with SLE or MS were genotyped in SLE and MS patients. The MS-associated rs17445836G allele was associated with anti-double-stranded DNA (dsDNA) autoantibodies in SLE patients (meta-analysis odds ratio=1.92). The same allele was associated with decreased serum IFN activity in SLE patients with anti-dsDNA antibodies, and with decreased type I IFN-induced gene expression in peripheral blood mononuclear cell from anti-dsDNA-negative SLE patients. In secondary progressive MS patients, rs17445836G was associated with decreased serum type I IFN. Rs17445836G was associated with increased IRF8 expression in SLE patient B cells. In summary, IRF8 rs17445836G is associated with human autoimmune disease characterized by low-type I IFN levels, and this may have pharmacogenetic relevance as type I IFN is modulated in SLE and MS. The association with autoantibodies and increased IRF8 expression in B cells supports a role for rs17445836G in humoral tolerance.

Interferon-beta-1b-induced short- and long-term signatures of treatment activity in multiple sclerosis.

Interferon beta (IFNß) reduces disease burden in relapsing-remitting multiple sclerosis (MS) patients. In this study, IFNß-1b-treated MS patient gene expression profiles and biological knowledgebases were integrated to study IFNß's pleiotropic mechanisms of action. Genes involved in immune regulation, mitochondrial fatty acid metabolism and antioxidant activity were discovered. Plausible mediators of neuronal preservation included NRF2, downregulation of OLA1, an antioxidant suppressor, and the antioxidant gene ND6, implicated in optic neuropathy and MS-like lesions. Network analysis highlighted IKBKE, which likely has a role in both viral response and energy metabolism. A comparative analysis of therapy-naive MS- and IFNß-associated gene expression suggests an IFNß insufficiency in MS. We observed more gene expression changes in long-term treatment than during acute dosing. These distinct short- and long-term effects were driven by different transcription factors. Multi-gene biomarker signatures of IFNß treatment effects were developed and subsequently confirmed in independent IFNß-1b-treated MS studies, but not in glatiramer acetate-treated patients.

Neuro-QOL: brief measures of health-related quality of life for clinical research in neurology.

OBJECTIVE: To address the need for brief, reliable, valid, and standardized quality of life (QOL) assessment applicable across neurologic conditions. METHODS: Drawing from larger calibrated item banks, we developed short measures (8-9 items each) of 13 different QOL domains across physical, mental, and social health and evaluated their validity and reliability. Three samples were utilized during short form development: general population (Internet-based, n = 2,113); clinical panel (Internet-based, n = 553); and clinical outpatient (clinic-based, n = 581). All short forms are expressed as T scores with a mean of 50 and SD of 10. RESULTS: Internal consistency (Cronbach α) of the 13 short forms ranged from 0.85 to 0.97. Correlations between short form and full-length item bank scores ranged from 0.88 to 0.99 (0.82-0.96 after removing common items from banks). Online respondents were asked whether they had any of 19 different chronic health conditions, and whether or not those reported conditions interfered with ability to function normally. All short forms, across physical, mental, and social health, were able to separate people who reported no health condition from those who reported 1-2 or 3 or more. In addition, scores on all 13 domains were worse for people who acknowledged being limited by the health conditions they reported, compared to those who reported conditions but were not limited by them. CONCLUSION: These 13 brief measures of self-reported QOL are reliable and show preliminary evidence of concurrent validity inasmuch as they differentiate people based upon number of reported health conditions and whether those reported conditions impede normal function.

Survival in MS: a randomized cohort study 21 years after the start of the pivotal IFNß-1b trial.

OBJECTIVE: To examine the effects of interferon beta (IFNß)-1b on all-cause mortality over 21 years in the cohort of 372 patients who participated in the pivotal randomized clinical trial (RCT), retaining (in the analysis) the original randomized treatment-assignments. METHODS: For this randomized long-term cohort study, the primary outcome, defined before data collection, was the comparison of all-cause mortality between the IFNß-1b 250 µg and placebo groups from the time of randomization through the entire 21-year follow-up interval (intention-to-treat, log-rank test for Kaplan-Meier survival curves). All other survival outcomes were secondary. RESULTS: After a median of 21.1 years from RCT enrollment, 98.4%(366 of 372) of patients were identified, and, of these, 81 deaths were recorded (22.1% [81 of 366]). Patients originally randomly assigned to IFNß-1b 250 µg showed a significant reduction in all-cause mortality over the 21-year period compared with placebo (p = 0.0173), with a hazard ratio of 0.532 (95% confidence interval 0.314-0.902). The hazard rate of death at long-term follow-up by Kaplan-Meier estimates was reduced by 46.8% among IFNß-1b 250 µg-treated patients (46.0% among IFNß-1b 50 µg-treated patients) compared with placebo. Baseline variables did not influence the observed treatment effect. CONCLUSIONS: There was a significant survival advantage in this cohort of patients receiving early IFNß-1b treatment at either dose compared with placebo. Near-complete ascertainment, together with confirmatory findings from both active treatment groups, strengthens the evidence for an IFNß-1b benefit on all-cause mortality. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that early treatment with IFNß-1b is associated with prolonged survival in initially treatment-naive patients with relapsing-remitting multiple sclerosis.

Recommendations for a Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS).

BACKGROUND: Cognitive impairment in MS impacts negatively on many patients at all disease stages and in all subtypes. Full clinical cognitive assessment is expensive, requiring expert staff and special equipment. Test versions and normative data are not available for all languages and cultures. OBJECTIVE: To recommend a brief cognitive assessment for multiple sclerosis (MS) that is optimized for small centers, with one or few staff members, who may not have neuropsychological training and constructed to maximize international use. METHODS: An expert committee of twelve members representing the main cultural groups that have so far contributed considerable data about MS cognitive dysfunction was convened. Following exhaustive literature review, peer-reviewed articles were selected to cover a broad spectrum of cultures and scales that targeted cognitive domains vulnerable to MS. Each was rated by two committee members and candidates scales were rated on psychometric qualities (reliability, validity, and sensitivity), international application, ease of administration, feasibility in the specified context, and acceptability to patients. RESULTS: The committee recommended the Symbol Digit Modalities Test, if only 5 minutes was available, with the addition of the California Verbal Learning Test - Second Edition and the Brief Visuospatial Memory Test - Revised learning trials if a further 10 minutes could be allocated for testing. CONCLUSIONS: A brief cognitive assessment for MS has been recommended. A validation protocol has been prepared for language groups and validation studies have commenced.

Cross-sectional study assessing long-term safety of interferon-beta-1b for relapsing-remitting MS.

OBJECTIVE: The 16-Year Long-Term Follow-Up (LTF) to the pivotal interferon-beta-1b (IFNbeta-1b) trial explored clinical, MRI, cognitive, and patient-reported outcomes. Here, we report the safety assessments. METHODS: In the pivotal study, 372 patients were randomized to placebo (n = 123), IFNbeta-1b 50 microg (n = 125), or IFNbeta-1b 250 microg (n = 124) subcutaneously every other day for up to 5 years. Sixteen years later, patients were asked to participate in this cross-sectional follow-up study. No particular therapy was stipulated during follow-up. Adverse events experienced since the pivotal trial were recorded. Neutralizing antibodies (NAbs) to IFNbeta-1b were measured using the myxovirus protein A induction assay. Statistical analyses were descriptive. RESULTS: In total, 88.2% of patients (328/372) were identified. Some centers achieved 100% ascertainment, obviating selection bias. Treatment-related adverse events (e.g., leukopenia and liver and thyroid dysfunction) reported by LTF participants were in keeping with those previously established. Based on a follow-up period that includes 2,000 patient-years of IFNbeta-1b treatment, no new adverse events were observed that were associated with long-term IFNbeta-1b exposure. By LTF, NAbs to IFNbeta-1b disappeared in the majority (76%) of NAb-positive patients. NAb status during the pivotal study appeared to have no impact on long-term clinical and MRI outcomes. There were more deaths among patients assigned to placebo in the pivotal study (20/109 [18.3%]) compared with patients who received IFNbeta-1b 50 microg (9/108 [8.3%]) or IFNbeta-1b 250 microg (6/111 [5.4%]). CONCLUSION: The results from the 16-Year Long-Term Follow-Up study support the long-term safety of interferon-beta-1b therapy in multiple sclerosis. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that patients with relapsing-remitting MS taking IFNbeta-1b 50 microg or 250 microg subcutaneously every other day for up to 5 years, with subsequent unspecified treatment, have fewer deaths after 16 years of follow-up than similar patients on placebo for up to 5 years, with subsequent unspecified treatment (risk difference 11.5%, 95% confidence interval 4-19).

Analysis of clinical outcomes according to original treatment groups 16 years after the pivotal IFNB-1b trial.

BACKGROUND: Evidence for efficacy of disease-modifying drugs in multiple sclerosis (MS) comes from trials of short duration. We report results from a 16 y, retrospective follow-up of the pivotal interferon beta-1b (IFNB-1b) study. METHODS: The 372 trial patients were randomly assigned to placebo (n=123), IFNB-1b 50 microg (n=125) or IFNB-1b 250 microg (n=124) subcutaneously every other day for at least 2 y. Some remained randomised for up to 5 y but, subsequently, patients received treatment according to physicians' discretion. Patients were re-contacted and asked to participate. Efficacy related measures included MRI parameters, relapse rate, the Expanded Disability Status Scale, the Multiple Sclerosis Functional Composite Measure and conversion to secondary progressive MS. RESULTS: Of the 88.2% (328/372) of patients who were identified, 69.9% (260/372) had available case report forms. No differences in outcome between original randomisation groups could be discerned using standard disability and MRI measures. However, mortality rates among patients originally treated with IFNB-1b were lower than in the original placebo group (18.3% (20/109) for placebo versus 8.3% (9/108) for IFNB-1b 50 microg and 5.4% (6/111) for IFNB-1b 250 microg). CONCLUSIONS: The original treatment assignment could not be shown to influence standard assessments of long-term efficacy. On-study behaviour of patients was influenced by factors that could not be controlled with the sacrifice of randomisation and blinding. Mortality was higher in patients originally assigned to placebo than those who had received IFNB-1b 50 microg or 250 microg. The dataset provides important resources to explore early predictors of long-term outcome.

Mechanisms of action of disease-modifying agents and brain volume changes in multiple sclerosis.

Disease-modifying agents (DMAs), including interferon beta (IFNbeta) and glatiramer acetate (GA), are the mainstays of long-term treatment of multiple sclerosis (MS). Other potent anti-inflammatory agents like natalizumab and different types of chemotherapeutics are increasingly being used for treatment of MS, particularly in patients with breakthrough disease activity. Brain volume (BV) loss occurs early in the disease process, accelerates over time, and may be only partially affected by DMA therapy. Low-dose, low frequency IFNbeta administered once weekly and GA appear to partially reduce BV decline over the second and third years of treatment. High dose, high frequency IFNbeta demonstrated no clear effect on BV loss during this time period. Current evidence suggests that changes in BV after immunoablation may not be due entirely to the resolution of edema but may be related to potential chemotoxicity of high dose cyclophosphamide. Natalizumab reduces the development of BV decline in the second and third years of treatment. IV immunoglobulin showed a positive effect on decelerating BV reduction in relapsing and advanced stages of MS. These differences between DMAs may be explained by the extent of their therapeutic effects on inflammation and on the balance between inhibition or promotion of remyelination and neuronal repair in the CNS. We described the mechanisms of action by which DMAs induce accelerated, non-tissue-related BV loss (pseudoatrophy) in the short term but, in the long run, may still potentially lead to permanent BV decline. The effects of corticosteroid therapy on changes in BV in patients with MS help clarify the mechanisms through which potent anti-inflammatory treatments may prevent, stabilize, or induce BV loss.

Combining beta interferon and atorvastatin may increase disease activity in multiple sclerosis.

OBJECTIVE: To explore whether high-dose atorvastatin can be administered safely to persons with relapsing-remitting multiple sclerosis (MS) taking thrice weekly, 44 microg dose subcutaneous interferon beta-1a. METHODS: Persons with clinically stable, relapsing-remitting MS, on standard high-dose subcutaneous interferon beta-1a, were randomized in a double-blind fashion to receive either placebo or atorvastatin at dosages of 40 or 80 mg/day for 6 months. Blinded neurologic examinations and brain MRI readings were obtained at months 0, 3, 6, and 9. Laboratory blood testing was performed monthly. Main outcome measures were the determination of drug toxicity using blood tests and ECG and determination of MS-related disease activity, either clinical relapses or new or contrast-enhancing lesions on MRI. RESULTS: Twenty-six subjects received at least one dose of study drug. Ten of 17 subjects on either 80 mg or 40 mg of atorvastatin per day had either new or enhancing T2 lesions on MRI or clinical relapses. One of the nine subjects on placebo had a relapse with active lesions on MRI. The subjects receiving atorvastatin were at greater risk for either clinical or MRI disease activity compared to placebo (p = 0.019). Significant changes in blood tests were noted only for lower cholesterol levels in subjects receiving atorvastatin. CONCLUSION: The combination of 40 or 80 mg atorvastatin with thrice weekly, 44 microg interferon beta-1a in persons with multiple sclerosis resulted in increased MRI and clinical disease activity. Caution is suggested in administering this combination.

Minor salivary gland inflammation in Devic's disease and longitudinally extensive myelitis.

Devic's disease is often considered as a variant of multiple sclerosis (MS). However, evidence suggests that Devic's disease may be distinct from MS. Devic's disease can coexist with connective tissue diseases, particularly Sjögren's disease, but this association is rare with MS. Diagnosis of Sjögren's disease in patients with neurological symptoms is often difficult. During early stages of Sjögren's disease, patients may not fulfill all criteria for Sjögren's disease. A high percentage of patients with Sjögren's disease have inflammatory infiltrates in minor salivary glands, and this may be a reliable indicator of early or subclinical disease. We show high prevalence (80%) of salivary gland inflammation in Devic's disease and longitudinally extensive transverse myelitis (LETM). We diagnosed 16 patients with Devic's disease, and 2 of these satisfied criteria for Sjögren's disease as did 2 of 9 patients with LETM. Anti-SSA/B titers were infrequently elevated. Although most did not satisfy criteria for Sjögren's disease. 9 of 12 Devic's disease patients and 7 of 8 LETM patients had severe salivary gland inflammation. Thus: (1) patients with Devic's disease or with LETM who have positive labial biopsies but do not satisfy criteria for Sjögren's disease could have subclinical Sjögren's diseases. Alternatively, (2) as patients with Devic's disease have elevated titers of several autoantibodies, so there may exist a set of antibodies that react with antigens in minor salivary glands and cause inflammation. Minor salivary gland biopsy is more sensitive than anti-SSA/B serology in providing histological evidence for possible Sjögren's disease with CNS lesions.

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-naïve 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-naïve 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.

Neutralizing antibodies to interferon beta: assessment of their clinical and radiographic impact: an evidence report: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology.

The clinical and radiologic impact of developing neutralizing antibodies (NAbs) to interferon beta (IFNbeta) while on this therapy for multiple sclerosis (MS) is assessed. On the basis of Class II and III evidence, it is concluded that treatment of patients with MS with IFNbeta (Avonex, Betaseron, or Rebif) is associated with the production of NAbs (Level A). NAbs in the serum are probably associated with a reduction in the radiographic and clinical effectiveness of IFNbeta treatment (Level B). In addition, the rate of NAb production is probably less with IFNbeta-1a treatment than with IFNbeta-1b treatment, although the magnitude and persistence of this difference is difficult to determine (Level B). Finally, it is probable that there is a difference in seroprevalence due to variability in the dose of IFNbeta injected or in the frequency or route of its administration (Level B). Regardless of the explanation, it seems clear that IFNbeta-1a (as it is currently formulated for IM injection) is less immunogenic than the current IFNbeta preparations (either IFNbeta-1a or IFNbeta-1b) given multiple times per week subcutaneously (Level A). However, because NAbs disappear in some patients even with continued IFNbeta treatment (especially in patients with low titers), the persistence of this difference is difficult to determine (Level B). Although the finding of sustained high-titer NAbs (>100 to 200 NU/mL) is associated with a reduction in the therapeutic effects of IFNbeta on radiographic and clinical measures of MS disease activity, there is insufficient information on the utilization of NAb testing to provide specific recommendations regarding when to test, which test to use, how many tests are necessary, or which cutoff titer to apply (Level U).

Safety and tolerability of interferon beta-1b in pediatric multiple sclerosis.

BACKGROUND: Immunomodulatory therapies are widely used in adults with multiple sclerosis (MS) and safety and tolerability is well-established. Although at least 5% of all patients with MS experience the clinical onset of their disease prior to age 18 years, the available literature on safety and tolerability of immunomodulatory therapies for pediatric-onset MS is limited. METHODS: The authors retrospectively reviewed safety and tolerability of interferon beta-1b (IFNbeta-1b) in a cohort of 43 children and adolescents treated for a mean of 29.2 months (SD 22.3 months). RESULTS: Mean age at start of IFNbeta-1b treatment was 13 years. Eight children were < or =10 years. Most common adverse events included flu-like syndrome (35%), abnormal liver function test (26%), and injection site reaction (21%). No serious or unexpected adverse events were reported. CONCLUSIONS: Although data on long-term effects on the maturing organ systems are lacking, the safety profile supports the safety and tolerability of interferon beta-1b (IFNbeta-1b) in children with multiple sclerosis and related diseases. All patients treated with IFNbeta-1b should undergo regular monitoring of liver function.

Abnormal levels of interferon-gamma receptors in active multiple sclerosis are normalized by IFN-beta therapy: implications for control of apoptosis.

Interferon-gamma is produced by immune cells before MS exacerbations, and exogenous IFN-gamma treatment causes MS attacks. IFN-beta production, conversely, rises after exacerbations. IFN-beta therapy ameliorates MS, possibly by lowering IFN-gamma secretion and inhibiting responses to IFN-gamma. IFN-gamma effects are regulated by IFN-gamma receptor (IFNGR) expression. IFN-gamma is pro-inflammatory at low IFNGR levels, but induces apoptosis in cells with high IFNGR levels. We studied effects of IFN-beta1a therapy on IFNGR expression on PMA/ionomycin-stimulated PBMNC's in 29 patients with active and stable MS. Surface IFNGR-alpha (the binding chain) and IFNGR-beta (signaling chain), as well as intracellular IFN-gamma and IL-10, were measured with flow cytometry. Before IFN-beta therapy, intracellular IL-10 was depressed and the IFN-gamma/IL-10 ratio was elevated in MS, particularly during clinical activity. With IFN-beta therapy IL-10 levels increased, suggesting that a Th2 deficit was reversed. The IFNGR-alpha chain was significantly elevated on lymphocytes in stable and active MS patients not receiving IFN-beta therapy. Expression of the IFNGR-beta chain was low during active untreated disease. After IFN-beta therapy, the IFNGR-beta/alpha ratio increased at 3 months and fell at 12 months. Increased susceptibility to apoptosis with high IFNGR-beta chain expression at 3 months is likely to remove activated T cells during IFN-beta therapy.

Psychometric evaluation of the Chicago Multiscale Depression Inventory in multiple sclerosis patients.

OBJECTIVE: The Chicago Multiscale Depression Inventory (CMDI), a comprehensive self-report measure of depression, has proven useful in the assessment of patients with chronic medical conditions. The objective of this study was to determine the validity of the CMDI in multiple sclerosis (MS) patients and explore the nature of depressive symptoms reported by people with MS. METHOD: Using a combined classical and modern psychometric approach, the factor structure of responses in MS patients was compared with that of a normative sample to confirm meaningful subtypes of depression in MS (mood, depressive cognition, and vegetative symptoms). Patient groups also were compared by disease severity to evaluate differences in depression associated with differences in disease severity. RESULTS: The results supported the factor structures of the measure, which was internally consistent, reliable, and factorially valid. Some items function differently in MS patients when compared with depressed patients and normals, offering a further opportunity to understand the unique clinical aspects of depression in people with MS compared with those without a concurrent physical illness. CONCLUSIONS: Use of the CMDI to assess separate dimensions of depression may help to clarify the complex interrelationships among aspects of depression and health-related behavior.

Monocyte activation in multiple sclerosis.

Monocytes, macrophages, and microglia have a central role in the CNS inflammation of MS. Monocytes are important in the earliest events in MS. Peripheral blood monocytes secrete prostaglandins before MS attacks. During clinical activity monocyte activation markers increase and IL-1 and TNF-alpha levels are elevated. Other monocyte products such as IL-10 reduce inflammation. IL-10 mRNA in MNC is increased during stable disease. Manipulation of monokine secretion and expression of monocyte surface proteins are reasonable approaches for immune therapy of MS.

Effects of an anti-IL-10 monoclonal antibody on rIFNbeta-1b-mediated immune modulation. Relevance to multiple sclerosis.

The mechanism of action of recombinant IFNbeta1b (IFNbeta-1b), as a therapy for multiple sclerosis (MS), is still unknown but may result from the enhancement of ConA-induced suppressor cell function and the inhibition of IFNgamma secretion by lymphocytes. We previously demonstrated that IFNbeta-1b stimulated modest amounts of IL-10 secretion by monocytes and IL-10 activity, as cytokine synthesis inhibitory factor, was normal in MS. To determine whether IL-10 plays a role in IFNbeta-1b modulation of immune function in MS, we studied ConA-induced suppressor cell function and IFNgamma production in presence of IFNbeta-1b and an anti-IL-10 monoclonal antibody (mAb). Anti-IL-10 mAb significantly reduced the effect of IFNbeta-1b on ConA-induced suppressor cell function and IFNgamma production in healthy subjects; MS patients showed a trend of inhibition. We hypothesized that IL-10 may play a role in mediating the effects of IFNbeta-1b on suppressor cell function and IFNgamma production but suppressor molecules other than IL-10 could be also involved.

Increased CD80(+) B cells in active multiple sclerosis and reversal by interferon beta-1b therapy.

Costimulatory molecules help determine T cell responses. CD80 (B7-1) and CD86 (B7-2), costimulatory proteins on antigen-presenting cells, bind to CD28 on T cells. When costimulation is coupled with a signal through the T cell receptor (TCR), T cell proliferation and cytokine secretion are induced. However, TCR signaling without CD80/CD86CD28 costimulation causes anergy. During multiple sclerosis (MS) exacerbations, circulating immune cells are activated, Th1 cytokine levels in the blood are elevated, and blood-derived immune cells destroy brain oligodendroglia. In the experimental autoimmune encephalomyelitis model of MS, CD80 on antigen-presenting cells induces Th1 cell responses; CD86 enhances generation of Th2 cells. Variation in CD80 and CD86 expression is likely to influence immune regulation in MS. We demonstrate that the number of circulating CD80(+) lymphocytes is increased significantly during MS exacerbations, but is normal in stable MS. These CD80(+) lymphocytes are predominantly B cells, based on two-color flow cytometry. The number of CD71(+) and HLA-DR+ lymphocytes and monocytes is also increased in active MS. Therapy with IFN beta-1b markedly reduces the number of circulating CD80(+) B cells and increases CD86(+) monocyte number. HLA-DR+, CD71(+), and CD25(+) mononuclear cell numbers are also reduced by therapy. The number of CD80(+) cells may be a useful surrogate marker during IFN-beta therapy, and reduction of CD80-mediated costimulation may be one therapeutic mechanism by which IFN-beta acts in MS.