Transforming growth factor beta1 (TGFbeta1) mRNA level correlates with magnetic resonance imaging disease activity in multiple sclerosis patients

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

INTRODUCTION

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

Mood Symptoms and Chronic Fatigue Syndrome Due to Relapsing-Remitting Multiple Sclerosis Are Associated with Immune Activation and Aberrations in the Erythron

BACKGROUND

Multiple sclerosis (MS) is a chronic autoimmune and neuroinflammatory disease of the central nervous system characterized by peripheral activation of immune-inflammatory pathways which culminate in neurotoxicity causing demyelination of central neurons. Nonetheless, the pathophysiology of relapsing-remitting MS (RRMS)-related chronic fatigue, depression, anxiety, cognitive impairments, and autonomic disturbances is not well understood.

OBJECTIVES

The current study aims to delineate whether the remitted phase of RRMS is accompanied by activated immune-inflammatory pathways and if the latter, coupled with erythron variables, explain the chronic fatigue and mood symptoms due to RRMS.

MATERIAL AND METHODS

We recruited 63 MS patients, 55 in the remitted phase of RRMS and 8 with secondary progressive MS, and 30 healthy controls and assessed erythron variables, and used a bio-plex assay to measure 27 serum cytokines.

RESULTS

A significant proportion of the MS patients (46%) displayed activation of the immune-inflammatory response (IRS) and compensatory immune response (CIRS) systems, and T helper (Th)1 and Th17 cytokine profiles. Remitted RRMS patients showed increased chronic fatigue, depression, anxiety, physiosomatic, autonomic, and insomnia scores, which could partly be explained by M1 macrophage, Th1, Th-17, growth factor, and CIRS activation, as well as aberrations in the erythron including lowered hematocrit and hemoglobin levels.

CONCLUSIONS

Around 50% of remitted RRMS patients show activation of immune-inflammatory pathways in association with mood and chronic-fatigue-like symptoms. IRS and CIRS activation as well as the aberrations in the erythron are new drug targets to treat chronic fatigue and affective symptoms due to MS.

The role of TGF-β superfamily signaling in neurological disorders

The TGF-β superfamily signaling is involved in a variety of biological processes during embryogenesis and in adult tissue homeostasis. Faulty regulation of the signaling pathway that transduces the TGF-β superfamily signals accordingly leads to a number of ailments, such as cancer and cardiovascular, metabolic, urinary, intestinal, skeletal, and immune diseases. In recent years, a number of studies have elucidated the essential roles of TGF-βs and BMPs during neuronal development in the maintenance of appropriate innervation and neuronal activity. The new advancement implicates significant roles of the aberrant TGF-β superfamily signaling in the pathogenesis of neurological disorders. In this review, we compile a number of reports implicating the deregulation of TGF-β/BMP signaling pathways in the pathogenesis of cognitive and neurodegenerative disorders in animal models and patients. We apologize in advance that the review falls short of providing details of the role of TGF-β/BMP signaling or mechanisms underlying the pathogenesis of neurological disorders. The goal of this article is to reveal a gap in our knowledge regarding the association between TGF-β/BMP signaling pathways and neuronal tissue homeostasis and development and facilitate the research with a potential to develop new therapies for neurological ailments by modulating the pathways.

TGF-β Family Signaling in Neural and Neuronal Differentiation, Development, and Function

Signaling by the transforming growth factor β (TGF-β) family is necessary for proper neural development and function throughout life. Sequential waves of activation, inhibition, and reactivation of TGF-β family members regulate numerous elements of the nervous system from the earliest stages of embryogenesis through adulthood. This review discusses the expression, regulation, and function of TGF-β family members in the central nervous system at various developmental stages, beginning with induction and patterning of the nervous system to their importance in the adult as modulators of inflammatory response and involvement in degenerative diseases.

The influence of sex hormones on cytokines in multiple sclerosis and experimental autoimmune encephalomyelitis: a review

The female predominance of multiple sclerosis (MS) has suggested that hormonal differences between the sexes must confer some protective effect on males or enhance the susceptibility of females to this disease. There has been evidence that gonadal hormones can modulate the immune response regulated by antigen presenting cells and T cells. These cells control the immune response by the production of interacting pro- and anti-inflammatory cytokines. The first include the acute phase pro-inflammatory cytokines of the innate immune response as well as the T-helper 1 (Th1) cytokines, while the later contain the Th2 cytokines as well as the suppressor cytokines. There is some evidence that MS and experimental autoimmune encephalitis (EAE) are Th1 cell-mediated diseases. For this reason many studies have been done to influence the pro-inflammatory cytokine production of these Th1 cells in favour of an anti-inflammatory immune response as mediated by Th2 cells. However the role of the regulatory T cells in this context is not clearly understood. Here we review the studies concerning the role of sex hormones on the cytokine production in relation to the disease course of MS and EAE and in particular in the light of the recent revival of the regulatory T cells and their suppressive cytokines.

The role of pro- and anti-inflammatory cytokines in the pathogenesis of spontaneous canine CNS diseases

Dogs are comparatively frequently affected by various spontaneously occurring inflammatory and degenerative central nervous system (CNS) conditions, and immunopathological processes are a hallmark of the associated neuropathology. Due to the low regenerative capacity of the CNS a sophisticated understanding of the underlying molecular basis for disease initiation, progression and remission in canine CNS diseases represents a prerequisite for the development of novel therapeutical approaches. In addition, as many spontaneous canine CNS diseases share striking similarities with their human counterpart, knowledge about the immune pathogenesis may in part be translated for a better understanding of certain human diseases. In addition to cytokine-driven differentiation of peripheral leukocytes including different subsets of T cells recent research suggests a pivotal role of these mediators also in phenotype polarization of resident glial cells. Cytokines thus represent the key mediators of the local and systemic immune response in CNS diseases and their orchestration significantly decides on either lesion progression or remission. The aim of the present review is to summarize the growing number of data focusing on the molecular basis of the immune response during spontaneous canine CNS diseases and to detail the effect of cytokines on the immune pathogenesis of selected idiopathic, infectious, and traumatic canine CNS diseases. Steroid-responsive meningitis arteritis (SRMA) represents a unique idiopathic disease of leptomeningeal blood vessels characterized by excessive IgA secretion into the cerebrospinal fluid. Recent reports have given sophisticated insights into the cytokine-driven, immune-mediated pathogenesis of SRMA that is characterized by a biased T helper 2 cell response. Canine distemper associated leukoencephalitis represents an important spontaneously occurring disease that allows investigations on the basic pathogenesis of immune-mediated myelin loss. It is characterized by an early virus-induced up-regulation of pro-inflammatory cytokines with chronic bystander immune-mediated demyelinating processes. Lastly, canine spinal cord injury (SCI) shares many similarities with the human counterpart and most commonly results from intervertebral disk disease. The knowledge of its pathogenesis is largely restricted to experimental studies in rodents, and the impact of immune processes that accompany secondary injury is discussed controversially. Recent investigations on canine SCI highlight the pivotal role of pro-inflammatory cytokine expression that is paralleled by a dominating reaction of microglia/macrophages potentially indicating a polarization of these immune cells into a neurotoxic and harmful phenotype. This report will review the role of cytokines in the immune processes of the mentioned representative canine CNS diseases and highlight the importance of cytokine/cytokine interaction as a useful therapeutic target in canine CNS diseases.

Increase of pro-inflammatory cytokine expression in non-demyelinating early cerebral lesions in nervous canine distemper

Canine distemper virus (CDV) infection of the central nervous system results in lesions of the gray and white matter. While a biphasic disease process has been discussed for leukoencephalitis with a prominent loss of viral protein expression, polioencephalitis has been associated with virus persistence. Using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), expression of pro- and anti-inflammatory cytokines such as interleukin (IL)-1beta, IL-2, IL-6, IL-8, IL-10, IL-12, tumor necrosis factor-alpha (TNF)-alpha, interferon (IFN)-gamma, and transforming growth factor (TGF)-beta were studied in the cerebra of distemper dogs with white matter lesions in the cerebellum. Additionally, cytokine values were correlated with the degree of CDV infection, major histocompatibility complex class II (MHC II) expression, and infiltration of CD4-, CD8-, and CD3epsilon-positive lymphocytes. Cerebral CDV infection was not associated with detectable light microscopic lesions or infiltration of B and T lymphocytes. However, an increasing number of CDV-antigen-positive cells was associated with an upregulation of MHC II antigen. RT-PCR results revealed a significant upregulation of IL-6, IL-8, IL-12, and TNF-alpha in the cerebra of distemper dogs, whereas IL-10 and TGF-beta showed no significant increase. Elevated cytokine values were directly related to the presence of CDV antigen and MHC II upregulation. However, succeeding increases of the latter did not result in an additional proportional elevation of cytokine expression values. In summary, the present study demonstrates the expression of pro-inflammatory cytokines by resident neural cells following CDV infection. Furthermore, the lack of light microscopic changes indicates that additional factors besides cytokines are necessary for the development of a distemper-characteristic neuropathology.

Genes implicated in multiple sclerosis pathogenesis from consilience of genotyping and expression profiles in relapse and remission

Background

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Although the pathogenesis of MS remains unknown, it is widely regarded as an autoimmune disease mediated by T-lymphocytes directed against myelin proteins and/or other oligodendrocyte epitopes.

Methods

In this study we investigated the gene expression profiles of peripheral blood cells from patients with RRMS during the relapse and the remission phases utilizing gene microarray technology. Dysregulated genes encoded in regions associated with MS susceptibility from genomic screens or previous trancriptomic studies were identified. The proximal promoter region polymorphisms of two genes were tested for association with disease and expression level.

Results

Distinct sets of dysregulated genes during the relapse and remission phases were identified including genes involved in apoptosis and inflammation. Three of these dysregulated genes have been previously implicated with MS susceptibility in genomic screens: TGFβ1, CD58 and DBC1. TGFβ1 has one common SNP in the proximal promoter: -508 T>C (rs1800469). Genotyping two Australian trio sets (total 620 families) found a trend for over-transmission of the T allele in MS in females (p < 0.13). Upregulation of CD58 and DBC1 in remission is consistent with their putative roles in promoting regulatory T cells and reducing cell proliferation, respectively. A fourth gene, ALOX5, is consistently found over-expressed in MS. Two common genetic variants were confirmed in the ALOX5 putatve promoter: -557 T>C (rs12762303) and a 6 bp tandem repeat polymorphism (GGGCGG) between position -147 and -176; but no evidence for transmission distortion found.

Conclusion

The dysregulation of these genes tags their metabolic pathways for further investigation for potential therapeutic intervention.

Polyunsaturated fatty acids in the pathogenesis and treatment of multiple sclerosis

Epidemiological, biochemical, animal model and clinical trial data described in this overview strongly suggest that polyunsaturated fatty acids, particularly n-6 fatty acids, have a role in the pathogenesis and treatment of multiple sclerosis (MS). Data presented provides further evidence for a disturbance in n-6 fatty acid metabolism in MS. Disturbance of n-6 fatty acid metabolism and dysregulation of cytokines are shown to be linked and a "proof of concept clinical trial" further supports such a hypothesis. In a randomised double-blind, placebo controlled trial of a high dose and low dose selected GLA (18:3n-6)-rich oil and placebo control, the high dose had a marked clinical effect in relapsing-remitting MS, significantly decreasing the relapse rate and the progression of disease. Laboratory findings paralleled clinical changes in the placebo group in that production of mononuclear cell pro-inflammatory cytokines (TNF-alpha, IL-1beta) was increased and anti-inflammatory TGF-beta markedly decreased with loss of membrane n-6 fatty acids linoleic (18:2n-6) and arachidonic acids (20:4n-6). In contrast there were no such changes in the high dose group. The improvement in disability (Expanded Disability Status Scale) in the high dose suggests there maybe a beneficial effect on neuronal lipids and neural function in MS. Thus disturbed n-6 fatty acid metabolism in MS gives rise to loss of membrane long chain n-6 fatty acids and loss of the anti-inflammatory regulatory cytokine TGF-beta, particularly during the relapse phase, as well as loss of these important neural fatty acids for CNS structure and function and consequent long term neurological deficit in MS.

Vitamin D and autoimmune disease--implications for practice from the multiple sclerosis literature

Recent studies and commentaries link vitamin D with several autoimmune diseases, including multiple sclerosis (MS). Adequate vitamin D intake reduces inflammatory cytokines through control of gene expression, thus inadequate vitamin D intake is suggested as a mechanism that could contribute to inflammation and, consequently, development of MS. Poor vitamin D status has been associated with increased risk for development of MS, and patients with MS may suffer consequences of vitamin D deficiency, such as bone loss. Animal studies and very limited human data suggest possible benefit from vitamin D supplementation in patients with MS. Based on the current state of research, a key principle for practicing dietetics professionals is to include vitamin D status in nutritional assessment. For those at risk for poor vitamin D status, intake can be enhanced by food-based advice and, when indicated, vitamin D supplementation.

Mounting evidence for vitamin D as an environmental factor affecting autoimmune disease prevalence

Low vitamin D status has been implicated in the etiology of autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, insulin-dependent diabetes mellitus, and inflammatory bowel disease. The optimal level of vitamin D intake required to support optimal immune function is not known but is likely to be at least that required for healthy bones. Experimentally, vitamin D deficiency results in the increased incidence of autoimmune disease. Mechanistically, the data point to a role for vitamin D in the development of self-tolerance. The vitamin D hormone (1,25-dihydroxy vitamin D(3)) regulates T helper cell (Th1) and dendritic cell function while inducing regulatory T-cell function. The net result is a decrease in the Th1-driven autoimmune response and decreased severity of symptoms. This review discusses the accumulating evidence pointing to a link between vitamin D and autoimmunity. Increased vitamin D intakes might decrease the incidence and severity of autoimmune diseases and the rate of bone fracture.

Evidence for cytokine dysregulation in multiple sclerosis: peripheral blood mononuclear cell production of pro-inflammatory and anti-inflammatory cytokines during relapse and remission

We investigated circulating anti-inflammatory and pro-inflammatory cytokines, and their ex vivo PBMC production in the absence or presence of the neuroantigens myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) and T cell mitogen (PHA) in MS patients in relapse and remission, patients with other neurological disorders (OND) and normal healthy controls. MS patients in relapse exhibited significantly increased PBMC production of TNF-alpha spontaneously compared with MS remission and healthy controls and with MBP compared with MS remission. Patients in relapse had significantly increased spontaneous, PHA- and MBP-induced PBMC IL-1beta production compared with remission MS, and was increased compared (PHA only) with OND and healthy controls. In relapse there was also significantly increased PBMC IFN-gamma production (PHA only) compared with remission and a significantly lower production of biologically active TGF-beta1 (PHA only) compared with remission MS and OND. In contrast, MS patients in remission produced significantly less spontaneous and MBP-induced TNF-alpha, spontaneous, PHA- and MBP-induced IL-1beta and PHA-induced IFN-gamma together with increased production of biologically active TGF-beta1. MOG non-specifically increased PBMC TNF-alpha and IL-1beta production in all groups. Pro-inflammatory cytokines in corresponding plasma samples were undetectable whilst the concentration of biologically active TGF-beta1 was the reverse of ex vivo PBMC findings. The increase in biologically active TGF-beta1 production ex vivo in OND patients, despite active disease, compared with the low level in the MS relapse may indicate a regulatory defect in MS. We conclude that the balance between biologically active TGF-beta1 and the pro-inflammatory TNF-alpha, IL-1beta and IFN-gamma is dysregulated during MS relapse-remission and that normal counter-regulatory mechanisms during the relapse phase are defective.

Persistent neutralizing antibodies abolish the interferon beta bioavailability in MS patients

BACKGROUND

MxA is an antiviral protein exclusively induced by type I interferons (IFN) and some viruses, and MxA gene expression is one of the most appropriate markers for measuring the biologic activity of exogenous IFNbeta.

METHODS

A new quantitative-competitive PCR method was used to quantify MxA mRNA in peripheral blood mononuclear cells of 99 treatment-naïve and 92 IFNbeta-treated patients with MS (22 Avonex, 17 Betaferon, and 53 Rebif-22). Every 3 months, IFNbeta-induced neutralizing antibodies (NAb) were evaluated in sera using a cytopathic effect assay. Three categories of patients were identified: NAb negative (NAb-), persistent NAb positive (NAb+, >or=2 consecutive positive samples), and isolated NAb+ (one positive sample).

RESULTS

Treatment-naïve patients expressed detectable MxA mRNA levels (mean = 36 +/- 32 fg MxA/pg glyceraldehyde-3-phosphate dehydrogenase (GAPDH); range 1 to 160) and an upper normal threshold was established (mean + 3 SD = 132 fg MxA/pg GAPDH). IFNbeta-treated patients exhibited more than 11-fold higher levels (mean = 412 +/- 282 fg MxA/pg GAPDH; range 16 to 1,172). However, 17 patients did not exhibit an increase in MxA mRNA level; 15 of these 17 patients showed a concurrent Nab+ titer. Moreover, 13 were persistent NAb+. Isolated NAb+ patients did not show a decrease in bioavailability of IFNbeta (n = 9; mean = 567 +/- 366 fg MxA/pg GAPDH; range 83 to 1,120). In NAb- patients, bioavailability was comparable among the three different IFNbeta preparations 12 hours after injection.

CONCLUSION

During IFNbeta therapy, the presence of NAb reduced or abolished bioavailability in a relevant percentage of patients. These data could be important for the early detection of patients with MS who are not responsive to IFNbeta therapy.

Cytokine profile in patients with multiple sclerosis following vitamin D supplementation

Multiple sclerosis (MS) patients were randomized, in a double blind design, and placed into either a vitamin D supplemented group or a placebo control group. As expected, serum 25-hydroxyvitamin D levels increased significantly following 6 month vitamin D supplementation (17+/-6 ng/ml at baseline to 28+/-8 ng/ml at 6 months). Vitamin D supplementation also significantly increased serum transforming growth factor (TGF)-beta 1 levels from 230+/-21 pg/ml at baseline to 295+/-40 pg/ml 6 months later. Placebo treatment had no effect on serum TGF-beta 1 levels. Tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and interleukin (IL)-13 were not different following vitamin D supplementation. IL-2 mRNA levels decreased following vitamin D supplementation but the differences did not reach significance. Vitamin D supplementation of MS patients for 6 months was associated with increased vitamin D status and serum TGF-beta 1.

In vivo effect of interferon-beta 1a on interleukin-12 and TGF-beta(1) cytokines in patients with relapsing-remitting multiple sclerosis

We have studied in vivo effect of interferon-beta 1a (IFN-beta 1a) (6 MIU once weekly i.m.) on interleukin-12 (IL-12) and transforming growth factor-beta(1) (TGF-beta(1)) serum levels during 6 months of therapy in group of 20 patients with relapsing-remitting multiple sclerosis (MS). IL-12 and TGF-beta(1) concentrations were measured by enzyme linked immunoabsorbent assay (ELISA). There was a significant increase of IL-12 levels in MS patients in comparison with control group, suggesting a role of this cytokine in immunity of MS. We have also found a significant increase of TGF-beta(1) levels after 6 months of therapy with IFN-beta 1a, however, there was no in vivo effect of the therapy on IL-12 levels. The results suggest that IFN-beta 1a may exert its action through up- regulation and increase secretion of TGF-beta(1).

Evaluation of bioavailability of three types of IFNbeta in multiple sclerosis patients by a new quantitative-competitive-PCR method for MxA quantification

Intracellular expression of human myxovirus protein A (MxA) is exclusively induced by type I IFNs (IFNalpha,beta,omega) or by some viruses and it is strongly increased under IFN treatment. We set up an internally controlled quantitative-competitive polymerase chain reaction (qc-PCR) that quantifies MxA mRNA expressed in human peripheral blood mononuclear cells (PBMC). Our qc-PCR is accurate because the mean ratio of copy number estimated by qc-PCR to that quantified spectrophotometrically is 1.08+/-0.03, moreover it is repeatable with high sensitivity (1 fg MxA/pg GAPDH). MxA mRNA was tested in 47 Relapsing-Remitting Multiple Sclerosis (RR-MS) untreated patients and in 48 patients treated with one of the 3 IFNbeta licensed for MS (24 with Rebif, 14 with Avonex and 10 with Betaferon). All the 48 treated patients were negative to IFNbeta neutralising antibodies (NABs) as tested in our laboratory using a cytopathic assay (CPE). MxA mRNA levels were detectable in all untreated patients (mean 24+/-18 fg MxA/pg GAPDH) and significantly higher levels were found in all the treated patients 12 h after IFNbeta administration (mean 499+/-325 fg MxA/pg GAPDH); furthermore, the three types of IFNbeta showed comparable bioavailability. Our data indicate that the bioavailability of the three available types of IFNbeta can be evaluated by MxA qc-PCR.

Cytokine expression in unstimulated PBMC of children with type 1 diabetes and subjects positive for diabetes-associated autoantibodies

The aim of this study was to evaluate possible changes in the circulating levels of interferon (IFN)-gamma, interleukin (IL)-4 and transforming growth factor (TGF)-beta in association with the autoimmune process leading to type 1 diabetes. Expression levels of mRNAs specific for each cytokine were determined in peripheral blood mononuclear cells (PBMC) by a multiplex reverse transcription-polymerase chain reaction (RT-PCR) followed by hybridization reactions with lanthanide-labelled probes and detection by time-resolved fluorometry. Newly diagnosed diabetic children had lower levels of IFN-gamma, IL-4 and TGF-beta 1 signals compared to their age- and sex-matched controls (P < 0.02, P < 0.005 and P < 0.005, respectively) and also the autoantibody-positive subjects had significantly lower levels of IL-4 and TGF-beta 1 in comparison with their matched controls (P = 0.0013 and P = 0.012). No significant differences were observed when comparing matched pairs of diabetic children and autoantibody-positive subjects. Our results suggest a systemic bias towards reduced production of T-helper cell type 2 cytokines (IL-4 and TGF-beta 1) during the autoimmune process, but there was also a reduced level of IFN-gamma expression in the periphery at the onset of clinical diabetes.

Sequence variation in the transforming growth factor-beta1 (TGFB1) gene and multiple sclerosis susceptibility

Genome screenings in multiple sclerosis (MS) have identified multiple susceptibility regions supporting a polygenic model for this disease. Evidence for linkage was consistently observed at ch.19q13 suggesting the presence of an MS gene(s) in this region. Several interesting candidate genes are encoded within this region, including transforming growth factor-beta 1 (TGFB1) and interleukin-11 (IL11). Both are multifunctional cytokines with significant and well-characterized immunomodulatory properties. We performed a comprehensive evaluation of common polymorphisms within the TGFB1 and IL11 loci and three closely flanking microsatellite markers (D19S421, CEA, D19S908) in 161 stringently ascertained and clinically characterized MS multiplex families using tests of both linkage (lod score, sib-pair analysis) and association (pedigree disequilibrium test or PDT). Patients and families were stratified by HLA-DR2 status to search for two-locus interactions. Suggestive evidence for linkage and association to CEA (lod score = 1.25, theta = 0.20, p = 0.015, respectively), located 0.4 cM from TGFB1, was observed in DR2 positive families only. Distinct clinical phenotypes were also examined and an association between a TGFB1 haplotype and a mild disease course was present (p = 0.008), raising the possibility that TGFB1 or a nearby locus may influence disease expression.

The protective effects of omega-6 fatty acids in experimental autoimmune encephalomyelitis (EAE) in relation to transforming growth factor-beta 1 (TGF-beta1) up-regulation and increased prostaglandin E2 (PGE2) production

Polyunsaturated fatty acids are known to affect the immune response and administration of the omega-6 fatty acid linoleic acid has been reported to be beneficial in multiple sclerosis (MS) and EAE. In this study we have investigated the effects of oral feeding of plant lipid rich in the omega-6 fatty acid gamma-linolenic acid from Borago officinalis on acute and relapse disease and the immune response in EAE using SJL mice. EAE was induced by an encephalitogenic peptide (92-106) of myelin oligodendrocyte glycoprotein (MOG), and mice were fed the plant lipid daily from 7 days after EAE induction to assess the effects on acute disease and from day 25 to assess the effects on disease relapse. The clinical incidence and histological manifestations of acute EAE, and the clinical relapse phase of chronic relapsing EAE (CREAE) were markedly inhibited by omega-6 fatty acid feeding. A significant increase in the production of TGF-beta1 in response to concanavalin A (Con A) at day 13 and a significant increase in TGF-beta1 and PGE2 to Con A, PPD and MOG peptide (92-106) at day 21 were detected in spleen mononuclear cells from fatty acid-fed mice. There was no difference in interferon-gamma, IL-4 and IL-2 production between the fatty acid-fed and control groups. Significantly higher TGF-beta mRNA expression was found in the spleens of omega-6 fatty acid-fed mice at day 21. There were no differences in spleen cell proliferative response to Con A, PPD and MOG peptide (92-106). Biochemical analysis of spleen cell membrane fatty acids revealed significant increases in the eicosanoid precursor fatty acids dihomo-gamma-linolenic acid and arachidonic acid in response to gamma-linolenic acid feeding, indicating rapid metabolism to longer chain omega-6 fatty acids. These results show that oral feeding of gamma-linolenic acid-rich plant lipid markedly affects the disease course of acute EAE and CREAE and is associated with an increase in cell membrane long chain omega-6 fatty acids, production of PGE2 and gene transcription and, on activation, secretion of TGF-beta1.