Genetic control of multiple sclerosis: increased production of lymphotoxin and tumor necrosis factor-alpha by HLA-DR2+ T cells

Tumor Necrosis Factor-Alpha (TNF-α-308 G>A) Polymorphism in High-grade Gliomas

BACKGROUND/AIM

High-grade gliomas (HGG) consist of anaplastic oligoastrocytomas, anaplastic oligodendrogliomas, anaplastic astrocytomas and glioblastoma multiforme. The present study aimed to evaluate TNF-α -308 G>A polymorphism in a Turkish population.

PATIENTS AND METHODS

This was a prospective case-control study that included 45 patients with HGG and 49 healthy individuals. All patients were operated for intracranial tumors and the pathology results consist of high grade (Grade3 and 4) glial tumors.

RESULTS

No significant differences were found between the HGG and control groups in terms of the median age (p=0.898). There were no significant differences with regard to gender (p=0.577). The TNF genotype frequency comparison between patients and controls was not statistically significant (p=0.598).

CONCLUSION

TNF genotype frequency comparison between the patients and controls was not statistically significant in the Turkish population tested. However, further studies are needed to evaluate the genotype and phenotype correlations in large cohorts of various ethnicities.

Serum immunologic markers in multiple sclerosis patients on continuous combined therapy with beta-interferon 1a, prednisone and azathioprine

Break-through symptoms (BTS) in multiple sclerosis (MS) patients on beta-interferon (beta-IFN) monotherapy are most frequently treated with a brief administration of steroids. Here, we report the results of monitoring serum immunologic markers recorded at three-month intervals for 1.5 years in responders to beta-INF 1a (Avonex) monotherapy ( n = 21) and MS patients placed on Avonex with prednisone ( n = 83) and Avonex, prednisone and azathioprine (AZA) ( n = 21) because of BTS. Compared to 23 healthy controls, patients on Avonex monotherapy and Avonex with prednisone, in individuals on Avonex, prednisone and AZA, a significant decrease in serum concentration of soluble intercellular adhesion molecule-1 (sICAM-1) ( P = 0.001) was established. Combined therapy with Avonex, prednisone and AZA was associated with a significant increase in the serum level of interleukin (IL)10 ( P < 0.001). Compared to Avonex monotherapy, combined therapy suppressed the serum level of IL12p40, antagonized elevation in the serum concentration of soluble IL2 receptor (sIL2R) and inhibited an increase in the serum soluble CD95 (sCD95) molecule. In patients studied, no significant differences in the serum level of IL18 and tumor necrosis factor-α (TNF-α) were established. These findings are important in understanding some of the immunoregulatory mechanisms induced by combined therapy in MS.

Death Ligands and Autoimmune Demyelination

Death ligands induce apoptosis, which is a cell suicide program leading mainly to selective elimination of an organism's useless cells. Importantly, the dying cell is an active participant in its own demise (“cellular suicide”). Under physiological conditions, apoptosis is most often found during normal cell turnover and tissue homeostasis, embryogenesis, induction and maintenance of immune tolerance, development of the nervous system, and endocrine-dependent tissue atrophy. However, apoptotic processes have also been suggested to contribute to the pathology of the autoimmune demyelinating disease multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis. Here, apoptosis plays a double role. On one hand, impaired apoptosis may result in increased numbers or persistence of activated myelinspecific T cells. On the other hand, local tissue damage involves apoptosis of oligodendrocytes and neurons, leading to the clinical symptoms. In this article, an overview is given of the current knowledge of the roles of apoptosis-mediating and immune regulatory death ligands of the tumor necrosis factor (TNF) family (TNF, lymphotoxin-beta, OX40L [CD134L], CD154 [CD40L], CD95L, CD70 [CD27L], CD153 [CD30L], 4-1BBL [CD137L], TRAIL, TWEAK, BAFF, GITRL) in the pathogenesis of MS and of their implications for related therapeutic strategies.

Inhibition of soluble tumour necrosis factor is therapeutic in experimental autoimmune encephalomyelitis and promotes axon preservation and remyelination

Tumour necrosis factor is linked to the pathophysiology of various neurodegenerative disorders including multiple sclerosis. Tumour necrosis factor exists in two biologically active forms, soluble and transmembrane. Here we show that selective inhibition of soluble tumour necrosis factor is therapeutic in experimental autoimmune encephalomyelitis. Treatment with XPro1595, a selective soluble tumour necrosis factor blocker, improves the clinical outcome, whereas non-selective inhibition of both forms of tumour necrosis factor with etanercept does not result in protection. The therapeutic effect of XPro1595 is associated with axon preservation and improved myelin compaction, paralleled by increased expression of axon-specific molecules (e.g. neurofilament-H) and reduced expression of non-phosphorylated neurofilament-H which is associated with axon damage. XPro1595-treated mice show significant remyelination accompanied by elevated expression of myelin-specific genes and increased numbers of oligodendrocyte precursors. Immunohistochemical characterization of tumour necrosis factor receptors in the spinal cord following experimental autoimmune encephalomyelitis shows tumour necrosis factor receptor 1 expression in neurons, oligodendrocytes and astrocytes, while tumour necrosis factor receptor 2 is localized in oligodendrocytes, oligodendrocyte precursors, astrocytes and macrophages/microglia. Importantly, a similar pattern of expression is found in post-mortem spinal cord of patients affected by progressive multiple sclerosis, suggesting that pharmacological modulation of tumour necrosis factor receptor signalling may represent an important target in affecting not only the course of mouse experimental autoimmune encephalomyelitis but human multiple sclerosis as well. Collectively, our data demonstrate that selective inhibition of soluble tumour necrosis factor improves recovery following experimental autoimmune encephalomyelitis, and that signalling mediated by transmembrane tumour necrosis factor is essential for axon and myelin preservation as well as remyelination, opening the possibility of a new avenue of treatment for multiple sclerosis.

TNF-alpha promoter polymorphisms in multiple sclerosis: no association with -308 and -238 alleles, but the -857 alleles in associated with the disease in Turkish patients

Dysregulation in the expression of pro- and anti-inflammatory cytokines is one of the milestones in multiple sclerosis (MS) development and progression. Tumour necrosis factor (TNF-alpha), a proinflammatory cytokine is believed to play an important role in MS pathogenesis. The objective of this study is to investigate the association between TNF-alpha promoter region (TNF-alpha-238, -308 and -857) and susceptibility to MS and clinical course of the disease. Eighty-six relapsing remitting MS patients and 150 sex-, age- and ethnic-matched controls were enrolled in the study. Genotyping was performed by PCR-RFLP method. We observed a statistically significant increase in TNF-alpha 857 CC genotype in MS patients than controls (P < 0.001) while TNF-alpha 857 CT genotype showed a significant negative correlation with MS patients (P = 0.033). No differences in the distribution of the TNF-alpha-238 and -308 alleles were observed. None of the three polymorphisms (-238, -308 and -857) did not show relation with disease duration, Expanded Disability Status Scale or age of onset. On the other hand, significant difference of TNF -857 CC genotype was identified with the low disease index (P = 0.025). Although the study group is small, the results indicate that TNF-alpha 857 CC genotype may cause susceptibility to MS in the Turkish population.

MHC gene related effects on microglia and macrophages in experimental autoimmune encephalomyelitis determine the extent of axonal injury

Myelin-oligodendrocyte-glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) in rats is a chronic inflammatory demyelinating disease of the central nervous system (CNS) strongly mimicking multiple sclerosis (MS). We determined the involvement of macrophages and microglia in the lesions of MOG-EAE in relation to different major histocompatibility complex (MHC, RT1 in rat) haplotypes. We used intra-RT1 recombinant rat strains with recombinations between the RT1a and RT1u haplotypes on the disease permissive LEW non-MHC genome. Activated microglia and macrophages were identified morphologically and by expression of ED1 and allograft inhibitory factor-1 (AIF-1), and differentiated by their morphological phenotype. White matter lesions contained more macrophages and less microglia compared to grey matter lesions. Similarly active lesions were mainly infiltrated by macrophages, while microglia were abundant in inactive demyelinated plaques. In addition, we found a highly significant genetic association between a macrophage or microglia dominated lesional phenotype, which was independent from location and activity of the lesions. This was not only the case in demyelinating plaques of chronic EAE, but also in purely inflammatory lesions of acute passive transfer EAE. Rat strains with an u-haplotype in both the Class II and the telomeric non-classical Class I region revealed inflammatory and demyelinating lesions, which were dominated by activated microglia. The a-haplotype in any of these regions was associated with macrophage dominated lesions. A comparison of lesions, exactly matched for stages of demyelinating activity in these different rat strains, showed that in spite of a similar extent of demyelination, axonal injury was significantly less in microglia compared to macrophage dominated lesions. Thus, our studies document a genetic influence of the MHC-region on the relative contribution of macrophages versus microglia in the pathogenesis of EAE.

Alpha B-crystallin is not a dominant peripheral T-cell autoantigen in multiple sclerosis amongst Sardinians

The heat shock protein alpha B-crystallin appears to be the dominantly recognized autoantigen in the early demyelinative process of multiple sclerosis (MS) in brain of patients. In Sardinia, MS is linked to human leucocyte antigen (HLA)-DR alleles that might influence the production of cytokines from peripheral lymphocytes. We tested the nature of peripheral anti-alpha B-crystallin-specific T-cell response in the context of predisposing HLA haplotypes both in MS patients and healthy controls. The alpha B-crystallin specific T-cell lines were generated by using the 'split-well' technique. The results indicate that the presence of short-term T-cell lines towards alpha B-crystallin is numerically comparable between the two groups and not restricted to MS-predisposing HLA-DR alleles. As for the T-cell characterization, CD4+ anti-alpha B-crystallin T cells secreting high levels of interferon-gamma are similarly identified in MS and healthy donors. In conclusion, the peripheral response towards the myelin antigen alpha B-crystallin is neither quantitatively nor qualitatively peculiar to MS, in contrast to the theoretical paradigm suggesting peripheral activation of myelin-reactive T cells to be the prerequisite for MS induction.

HLA-DR2 dose effect on susceptibility to multiple sclerosis and influence on disease course

Models of disease susceptibility in multiple sclerosis (MS) often assume a dominant action for the HLA-DRB1*1501 allele and its associated haplotype (DRB1*1501-DQB1*0602 or DR2). A robust and phenotypically well-characterized MS data set was used to explore this model in more detail. A dose effect of HLA-DR2 haplotypes on MS susceptibility was revealed. This observation suggests that, in addition to the role of HLA-DR2 in MS, two copies of a susceptibility haplotype further increase disease risk. Second, we report that DR2 haplotypes modify disease expression. There is a paucity of benign MS and an increase of severe MS in individuals homozygous for DR2. Concepts of the molecular mechanisms that underlie linkage and association of the human leukocyte antigen (HLA) region to MS need to be revised to accommodate these data.

Multiple sclerosis complexity in selected populations: the challenge of Sardinia, insular Italy

Several lines of evidence indicate a genetic contribution to multiple sclerosis (MS) both in terms of predisposition to the disease and of immunological mechanisms which are known to play crucial roles in MS pathogenesis. The presence of high- and low-risk areas for MS in neighbouring regions supports the theory that MS predisposition is influenced by a complex interaction of genetic and environmental factors. Therefore, the use of genetically homogeneous and geographically isolated populations becomes an increasing requirement to reduce biasing biological variables. Sardinians fulfil these conditions well because of their different phylogeny from Europeans and the unique selective pressures which shaped their genome. Sardinians display amongst the highest MS prevalence rates world-wide and increasing MS incidence rates over time. Also, MS in Sardinia is linked to distinct human leucocyte antigen (HLA) alleles and associated to different patterns of cytokine production from lymphoid cells of different HLA subtypes. In this context, recent findings and future perspectives on the peculiarities of Sardinian MS concerning genetic, immunological and epidemiological aspects are presented. So far, our results indicate that variations at the level of territorial distribution and HLA-association are present which render MS heterogeneous even in this ethnically homogeneous population.

The human T cell response to myelin oligodendrocyte glycoprotein: a multiple sclerosis family-based study

Myelin oligodendrocyte glycoprotein (MOG) is an encephalitogenic myelin protein and a likely autoantigen in human multiple sclerosis (MS). In this work, we describe the fine specificity and cytokine profile of T cell clones (TCC) directed against MOG in three nuclear families, comprised of four individuals affected with MS and their HLA-identical siblings. TCC were generated from PBMC by limiting dilution against a mixture of eleven 20-mer overlapping peptides corresponding to the encephalitogenic extracellular domain of human MOG (aa 1-120). The frequency of MOG peptide-reactive T cells was surprisingly high (range, 1:400 to 1:3,000) and, unexpectedly, cloning efficiencies were highest at low seeding densities of 10(2) or 10(3) PBMC per well. A total of 235 MOG peptide-reactive TCC were produced, all of which were CD4(+)CD8(-)TCRalphabeta(+)TCRgammadelta(-). All 11 MOG peptides were recognized by the TCC, and different epitopes of MOG appeared to be immunodominant in the HLA-identical siblings. The patterns of cytokine secretion by TCC from single individuals were generally similar. The healthy individuals exhibited Th2-, Th0-, and T regulatory cell 1-like cytokine profiles, whereas TCC from one sibling with MS had a striking Th1-like phenotype, producing high levels of IFN-gamma and TNF-alpha, and low IL-4 levels. Thus, MOG-reactive T cells appear to constitute an important part of the natural T cell repertoire, a finding that could contribute to the development of autoimmunity to this protein.

IgM antibodies identified by a DTT-ameliorated positive crossmatch do not influence renal graft outcome but the strength of the IgM lymphocytotoxicity is associated with DR phenotype

A positive crossmatch that is rendered negative by treating the serum with the IgM-reducing agent dithiothreitol (DTT) is generally reported not to influence short-term renal graft outcome. Its effect on long-term (> or = 3 years) cadaveric and live-donor transplant function, however, is less clear. We evaluated the effect of IgM antibodies in a DTT-ameliorated positive crossmatch (DTT-APXM) on long-term renal graft outcome in 1,290 consecutive cadaveric renal transplants (8-year survival) and 384 live-donor renal transplants (7-year survival) from patients transplanted between 1990 and 1999. The data show that 1- and 8-year graft survival for cadaveric renal transplants in patients with IgM antibodies (n=72) (DWFG censored = 91% and 65%; DWFG not censored = 90% and 60%) was not significantly different from the group without IgM antibodies (n = 1,218) (DWFG censored = 92% and 71%; DWFG not censored = 87% and 55%) (log-rank = 0.25 for DWFG censored, log-rank = 0.92 for DWFG not censored). The one- and seven-year graft survival for live-donor renal transplants in patients with IgM antibodies seen in a DTT-APXM (n = 22) (DWFG censored = 95% and 83%; DWFG not censored = 95% and 66%) was not significantly different from the group without IgM antibodies (n = 362) (DWFG censored = 94% and 81%; DWFG not censored = 92% and 73%) (log-rank = 0.61 for DWFG censored, log-rank = 0.89 for DWFG not censored). DR phenotype was found to be associated with the strong (>40% cell death) IgM reactivity in both black and white patients. In white patients, DR2 was more frequently seen with a strong IgM crossmatch (48.2%) than in molecularly typed controls (28.5%) (P < 0.03) and concomitant with that DR increase, DR4 was decreased in white patients (6.8%) compared with controls (25.5%) (P < 0.02). In black patients with strong IgM reactivity, DR6 was increased in patients (46.1%) compared with controls (20.5%) (P = 0.07) and concomitant with that DR6 increase, DR5 was decreased in frequency in black patients (7.6%) compared with controls (41%) (P < 0.03). These data show that long-term graft survival in renal transplantation is not negatively influenced by the presence of donor-reactive lymphocytotoxic antibodies in the crossmatch ameliorated by serum DTT treatment. They also suggest that the strength of the IgM antibody response is regulated in part by certain gene (s) of the DR region.

Elevated Bcl-X(L) levels correlate with T cell survival in multiple sclerosis

T cell resistance towards apoptotic elimination by activation-induced cell death (AICD) might be a crucial pathogenic feature of multiple sclerosis (MS). Since the Bcl-2 family is critically involved in the regulation of apoptosis, we investigated the protein expression of Bcl-2, Bcl-X(L), and Bax in peripheral blood mononuclear cells (PBMC) of 23 MS patients and 29 control subjects. An in vitro model of AICD, which exemplifies the elimination of antigen-reactive T cells in vivo, was used as an indication of T cell susceptibility or resistance towards apoptosis. Increased expression of the survival factor Bcl-X(L), which directly correlated with a resistance towards AICD, was observed in peripheral immune cells of MS patients. In contrast to Bcl-X(L), no differences were found in the protein expression of Bcl-2 and Bax between patients and controls. Our data indicate that the anti-apoptotic factor Bcl-X(L), responsible for T cell resistance towards apoptosis, might be an important factor in the MS pathogenesis and a potential target for therapeutic intervention.

Serum cytokine levels do not correlate with disease activity and severity assessed by brain MRI in multiple sclerosis

OBJECTIVE

Chronic and acute dysregulation of the cytokine network has been described in multiple sclerosis (MS). Inflammatory lesions in the central nervous system of MS patients can be assessed by brain magnetic resonance imaging (MRI). This study has been performed to investigate whether changes of cytokines correlate with morphological changes as determined by MRI.

MATERIALS AND METHODS

We included 46 patients with relapsing-remitting MS in the study. The serum concentrations of tumor necrosis factor-beta (TNF-beta), TNF receptor-1 (TNFR-1; 55 kDa) and TNFR-2 (75 kDa), interleukin-4 (IL-4), interleukin-10 (IL-10) and interferon-gamma (IFN-gamma) were measured by enzyme linked immunosorbent assay in all patients. Each parameter was correlated with clinical findings and brain MRI parameters. We measured both the number (lesion load) and cumulated area (disease burden) of all lesions on brain MRI. In addition, the number and cumulated area of those lesions showing signs of activity [Gadolinium (Gd)-enhancement, perifocal edema] were determined.

RESULTS

A non-significant trend (P < 0.05) was found only for the correlation of serum IFN-gamma levels and the number of active MRI lesions showing both Gd-enhancement and perifocal edema in the subgroup of patients (n=21) with active lesions. When corrected for multiple comparisons, this correlation was not significant anymore, as it was above the corrected P-value of 0.001. We could not observe any further correlation of cytokine levels and MRI parameters. However, TNF-beta serum levels were significantly (P < 0.05) elevated in the patient subgroups with higher number of lesions and disease burden, respectively.

CONCLUSION

Our data show that the determination of serum levels of the investigated cytokines and cytokine receptors is not useful as a tool to determine subclinical disease activity and severity as assessed by brain MRI.

HLA-DR 15 is associated with female sex and younger age at diagnosis in multiple sclerosis

BACKGROUND

The association between multiple sclerosis and class II alleles of the major histocompatibility complex, in particular the DRB1*1501-DQB1*0602 haplotype, is well established but their role in determining specific features of this clinically heterogeneous disease is unknown as few studies involving large sample sizes have been performed.

METHODS

729 patients with multiple sclerosis were typed for the HLA DR15 phenotype. All patients underwent clinical assessment and a detailed evaluation of their clinical records was undertaken.

RESULTS

The presence of DR15 was associated with younger age at diagnosis and female sex but there was no association with disease course (relapsing-remitting or secondary progressive v primary progressive type), disease outcome, specific clinical features (opticospinal v disseminated form), diagnostic certainty (clinically and laboratory supported definite v clinically probable multiple sclerosis), and paraclinical investigations including the presence of oligoclonal bands in the CSF or characteristic abnormalities on MRI imaging of the central nervous system.

CONCLUSION

Even though DR15 carriers are more likely to be female and prone to an earlier disease onset, the results indicate that there is no association with other specific clinical outcomes or laboratory indices examined here. This suggests that DR15 exerts a susceptibility rather than disease modifying effect in multiple sclerosis.

Polymorphisms in or near tumour necrosis factor (TNF)-gene do not determine levels of endotoxin-induced TNF production

Innate differences in tumour necrosis factor (TNF) production have been associated with susceptibility for and outcome of inflammatory diseases. Several studies have tried to identify whether polymorphisms in or near the TNF gene or other markers on the short arm of chromosome 6 (6p21) are related to differences in TNF production. Data on these associations are conflicting. Therefore, we conducted a study among 129 healthy individuals in which TNF production was determined upon stimulation with endotoxin in whole blood cultures. TNFa microsatellite, TNF single nucleotide polymorphisms at position +489, -238, -308 and -376 typing was performed. The data revealed that alleles of TNFa microsatellite and carriership of TNF polymorphisms were not related to TNF production. We conclude that the genes determing the differences in endotoxin-induced TNF production have not been yet identified.

Glial expression of tumor necrosis factor in transgenic animals: how do these models reflect the "normal situation"?

Recent progress in the field of experimental genetics, which enables the selective and conditional ablation or dysregulation in the expression of specific genes in mice, and its application to the study of experimentally inducible models for human disease, have contributed enormously to our understanding of the molecules and mechanisms that underlie autoimmunity and inflammation in the CNS. This article describes the lessons learned from the application of such technology to the study of the tumor necrosis factor-alpha (TNF) ligand/receptor system in the CNS. Important roles for TNF and its two membrane-bound receptors in the initiation and support of CNS inflammation, the development of CNS autoimmunity, and possibly in the resolution of T-cell-mediated disease, as well as their implications for our understanding of the "normal" cellular and molecular mechanisms that underlie CNS pathology, are discussed.

Peripheral blood cell bulk cultures are not suitable for the analysis of the genetic control of T-cell cytokine function

Recently evidence has been provided for a genetic control of T-cell dependent cytokine production by HLA-class II. Candidate genes in multiple sclerosis, a T-cell mediated autoimmune disease, are the disease-associated DR2, DQ6, Dw2 haplotype. Previous observations by us and others imply a HLA-DR2 dependent propensity of antigen-specific T-cell lines to produce increased amounts of TNF-alpha/beta. Here, we tested a possible association between HLA or disease status with cytokine production employing the simple and widely used method of bulk cultures. Peripheral blood cells of 48 patients and 68 healthy individuals were analyzed. We observed no significant differences of the cytokine production in relation to disease status or any HLA polymorphism. Our data indicate that, in contrast to monoclonal T-cell cultures, bulk cultures are not suitable to detect immunogenetic control of T-cell function.

No association of serum levels of interleukin-6 and its soluble receptor components with a genetic variation in the 3'flanking region of the interleukin-6 gene in patients with multiple sclerosis

Interleukin-6 (IL-6) plays an important role in the regulation of the inflammatory response in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Previous reports indicated that a variable number tandem repeat (vntr) polymorphism in the 3'flanking region of the IL-6 gene (C allele) is associated with altered activity of IL-6 in vivo. Therefore, we analyzed the frequency distribution of IL-6 gene C allele vntr poymorphism in 96 MS patients and 106 ethnically matched healthy controls. Moreover, possible correlations between genotypic differences of IL-6 gene and serum levels of IL-6, soluble IL-6 receptor (sIL6-R), soluble gp130 (sgp130), soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were investigated. There were no differences in the allelic distribution of the IL-6 gene C allele between MS patients and healthy controls, and no association of the IL-6 gene C allele with serum levels of IL-6, sIL-6R, spg130, sICAM and sVCAM-1 was found.

Multiple sclerosis associated amino acids of polymorphic regions relevant for the HLA antigen binding are confined to HLA-DR2

Among the candidate genes for multiple sclerosis (MS), the strongest influence is conferred by human leucocyte antigen (HLA) class II genes, in particular the DR2, DQ6, Dw2 haplotype (DRB1*1501, DQA1*0102, DQB1*0602). Similar to other autoimmune diseases, it is not clear yet how the presence of a specific HLA-DR or -DQ molecule translates into an increased disease susceptibility. Previous observations by us and others imply a HLA-DR2 dependent propensity of antigen-specific T-cell lines to produce increased amounts of TNF-alpha/beta as one mechanism how DR2 could contribute to susceptibility. In this article, we investigated the distribution of polymorphic stretches of the DRB1, DQA1, and DQB1 chains known to be relevant for antigen binding, in 66 unrelated patients with relapsing remitting MS and 210 unrelated controls. We found a significant association with disease for the appearance of proline at position 11, arginine at position 13, and alanine at position 71 of HLA-DRbeta1. Surprisingly, we identified only residues preferentially expressed in the MS group that were related to HLA-DR2. Thus, the contribution of HLA class II to the pathogenesis of MS is not mediated by allele-overlapping antigen binding sites, but is confined to the disease associated HLA allele.

Association of giant cell arteritis and polymyalgia rheumatica with different tumor necrosis factor microsatellite polymorphisms

OBJECTIVE

To determine whether giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are associated with different tumor necrosis factor (TNF) microsatellite polymorphisms.

METHODS

Typing of TNF microsatellite polymorphisms was carried out by molecular-based techniques on DNA obtained from a population sample of residents from Lugo, northwestern Spain. A case-control approach was used to compare 136 patients with GCA and/or PMR with 147 ethnically matched controls. The association of disease with TNF microsatellite polymorphisms was investigated using chi-square tests and multivariate logistic regression analyses.

RESULTS

Different TNF microsatellite associations were found with GCA and PMR. In patients with isolated GCA, the primary association was with TNFa2, which was independent of the GCA associations with HLA-DRB1*0401 and *0101. A negative association was found with TNFa10. In patients with isolated PMR, there was a positive association with TNFb3. This was found to be independent of the HLA-DRB1*13/*14 association in isolated PMR. TNFd4 was negatively associated with isolated PMR. Forward stepwise logistic regression analyses indicated that the strongest association with GCA was provided by the TNFa2 allele, although DRB1*0401 and *0101 were still associated. PMR was primarily associated with TNFb3. A direct comparison of TNF allele frequencies between isolated GCA and isolated PMR indicated that the main difference between these conditions occurred in the frequency of TNFa10.

CONCLUSION

GCA and PMR in individuals from northwestern Spain are associated with different TNF microsatellite polymorphisms. The primary TNF associations (TNFa2 and TNFb3) appear to influence susceptibility to these conditions independent of any HLA-DRB1 association.

TNF-alpha polymorphisms in multiple sclerosis: no association with -238 and -308 promoter alleles, but the microsatellite allele a11 is associated with the disease in French patients

Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, is believed to play an important role in multiple sclerosis (MS) pathogenesis. The objective of this study was to determine whether sequence variation in the TNF-alpha gene is associated with MS. Bi-allelic polymorphisms in the TNF-alpha promoter region (TNF-alpha -238 and -308) and microsatellite TNF-alpha were previously reported. We investigated these polymorphisms in 74 French patients with MS, compared with 75 controls. No significant differences regarding the TNF-alpha -238 and -308 polymorphisms were observed between MS patients and controls. Allele frequency for the a11 allele is in very significant association (P<0.0001) with MS, due in part to the association of the a11 allele with the HLA-DRB1*15 allele in patients.

HLA DRB1*1501 and intrathecal inflammation in multiple sclerosis

CD4 T cells are considered to be pivotal in the pathogenesis of multiple sclerosis (MS), and the human leukocyte antigen (HLA) haplotype associated with DRB1*1501 confers susceptibility to MS in patients of Northern European descent. Some previous studies have suggested an association of DRB1*1501 with T- and B-cell reactivity to specific myelin protein peptides, other studies suggested an association with enhanced cytokine production or intrathecal immunoglobulin (Ig) synthesis. In order to further assess the role of DRB1*1501 in the pathogenesis of MS, we studied intrathecal inflammation and T-cell phenotypes in patients with possible onset symptoms or clinically definite MS. Presence of DRB1*1501 was associated with higher levels of cerebrospinal fluid (CSF) inflammation as assessed by IgG synthesis levels and higher levels of matrix metalloproteinase-9 activity. DRB1*1501-positive patients also had a lower percentage of T cells in CSF expressing HLA-DR without co-expressing CD25. These findings suggest that enhanced intrathecal inflammation and an altered T-cell activation status may be of importance in conferring the DRB1*1501-associated susceptibility to MS.

T lymphocytes activated by persistent viral infection differentially modify the expression of metalloproteinases and their endogenous inhibitors, TIMPs, in human astrocytes: relevance to HTLV-I-induced neurological disease

Activation of T lymphocytes by human pathogens is a key step in the development of immune-mediated neurologic diseases. Because of their ability to invade the CNS and their increased secretion of proinflammatory cytokines, activated CD4+ T cells are thought to play a crucial role in pathogenesis. In the present study, we examined the expression of inflammatory mediators the cytokine-induced metalloproteinases (MMP-2, -3, and -9) and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMP-1, -2, and -3), in human astrocytes in response to activated T cells. We used a model system of CD4+ T lymphocytes activated by persistent viral infection (human T lymphotropic virus, HTLV-I) in transient contact with human astrocytes. Interaction with T cells resulted in increased production of MMP-3 and active MMP-9 in astrocytes despite increased expression of endogenous inhibitors, TIMP-1 and TIMP-3. These data suggest perturbation of the MMP/TIMP balance. These changes in MMP and TIMP expression were mediated, in part, by soluble factors (presumably cytokines) secreted by activated T cells. Integrin-mediated cell adhesion is also involved in the change in MMP level, since blockade of integrin subunits (alpha1, alpha3, alpha5, and beta1) on T cells resulted in less astrocytic MMP-9-induced expression. Interestingly, in CNS tissues from neurological HTLV-I-infected patients, MMP-9 was detected in neural cells within the perivascular space, which is infiltrated by mononuclear cells. Altogether, these data emphasize the importance of the MMP-TIMP axis in the complex interaction between the CNS and invading immune cells in the context of virally mediated T cell activation.

Interaction between tumor necrosis factor microsatellite polymorphisms and the HLA-DRB1 shared epitope in rheumatoid arthritis: influence on disease outcome

OBJECTIVE

To investigate whether interactions between tumor necrosis factor (TNF) microsatellite polymorphisms and the HLA-DRB1 shared epitope (SE) are associated with disease severity in rheumatoid arthritis (RA), and to determine if such associations are the same in male and female patients.

METHODS

Genotyping for the TNFa microsatellite and HLA-DRB1 was carried out on 157 RA patients with established disease (duration >5 years). Disease severity measures included radiographic damage (the Larsen method), functional assessment by the Health Assessment Questionnaire, history of joint surgery, and global appraisal of outcome by means of a visual analog scale score. The association of severity measures with TNFa microsatellite polymorphisms stratified by SE status, and the interaction between TNFa and the SE, were investigated using stratified analyses and multiple or logistic regression analyses.

RESULTS

No significant associations were observed between any single TNFa microsatellite polymorphism and disease severity, although preliminary evidence for an interaction between TNFa6 and TNFa11 was obtained. In the presence of the SE, a significantly worse outcome was associated with individuals carrying TNFa6, and a significant interaction (P = 0.04-0.006) was found between these alleles for all the outcome measures examined except history of joint surgery. In the absence of the SE, the TNFa6 allele was associated with significantly better outcome scores. When examined by sex, significant associations between the TNFa6/SE haplotype and disease outcome measures were found only in females. No statistically significant interactions were found in males, although the TNFa6/SE haplotype was still associated with the worst outcome scores.

CONCLUSION

The association of the SE with disease severity in RA is influenced by an interaction with the TNFa6 microsatellite polymorphism. This interaction appears to be acting predominantly in female patients, although the trend is similar in the smaller percentage of males carrying the TNFa6/SE haplotype.

Tumor necrosis factor microsatellite polymorphisms in Italian glioblastoma patients

Tumor necrosis factor (TNF) genes map on the short arm of chromosome 6 and have been described to contain several polymorphic regions, the most informative of which are TNFa (13 alleles) and TNFb (8 alleles) microsatellites. We analyze TNFa and TNFb microsatellite polymorphisms in 58 Italian patients with glioblastoma (GBL) and 95 unrelated healthy controls. At the TNFb locus, we detected a statistically significant decrease in the TNFb4 allele in GBL patients compared with the controls (P = 0.002; Pcorr = 0.015). Among the patients, 8 were homozygous TNFb4 (+/+), 23 were TNFb4 heterozygous (+/-), and 27 were negative for TNFb4 (-/-). In a comparison with the controls, we detected a statistically significant difference (P = 0.017). In fact, although no difference was detected in +/-, statistically significant differences were detected both for an increase in -/- and for a decrease in +/+ in the patient groups (P = 0.006 and P = 0.047, respectively). These data suggest that TNFb4-negative individuals might preferentially develop a Th2-type immune response that could lead to a reduction in antitumor activity.

Genetic susceptibility to multiple sclerosis in Sardinians: an immunological study

OBJECTIVES

We studied the in vitro production of variably MS-related cytokines from Sardinian MS and healthy donors bearing the two "Sardinian" MS-associated HLA-DR alleles: DR3 and DR4, with the purpose to evidentiate possible differences in their immune response.

MATERIALS AND METHODS

ELISA were used for detection of cellular products by mitogen-activated peripheral blood mononuclear cells.

RESULTS

PHA-activated HLA-DR4+/DR3- mononuclear cells produce significantly higher amounts of TNF-alpha compared with the DR3+/DR4-. In addition, homozygous HLA-DR3+ mononuclear cells from MS patients produce significantly lower amounts of IL-10 than those from homozygous HLA-DR3+ healthy donors.

CONCLUSION

The abnormal production of detrimental or regulatory cytokines may account for the genetic susceptibility to MS in different HLA-subgroups of Sardinian MS patients.

Cytokine mRNA profile of myelin basic protein reactive T-cell clones in patients with multiple sclerosis

Autoimmune mechanisms involving T-cell responses to (a) myelin autoantigen(s), such as myelin basic protein (MBP), are thought to contribute to the pathogenesis of multiple sclerosis (MS). Cytokines may play a central role in the regulation of the pathogenic autoimmune responses in MS and the mediation of tissue damage in the disease. To study the cytokine expression of myelin reactive T-cells in MS, we determined the cytokine mRNA levels in a panel of blood derived MBP-specific T-cell clones derived from MS patients (33 clones) and normal controls (21 clones), using a novel quantitative RT-PCR method. Our results demonstrate that MBP-specific T-cells, both from MS patients and control subjects, predominantly display a Th1- or Th0-like cytokine pattern. Although MS clones express higher levels of TNFalpha and IL-10 mRNA, these differences do not reach statistical significance. Interestingly, significantly increased TNFalpha and IFNgamma mRNA levels were observed among clones derived from HLA-DR2 positive versus HLA-DR2 negative MS patients. This HLA halpotype is known to be associated with MS. The high levels of TNFalpha and IFNgamma mRNA observed in MBP-reactive T-cell clones from MS patients indicate an important role of these cytokines in the disease process. Our data lend further support to the pathogenic role of MBP-reactive T-cells in MS.

Human myelin basic protein specific T cell lines display differential cytotoxicity against astrocytes, but are consistently cytotoxic against monocytes

In experimental allergic encephalomyelitis (EAE) myelin basic protein (MBP) specific T cells differ in their encephalitogenic potential. To investigate the functional diversity of human MBP specific T cell lines, we analysed their cytotoxic activity against human astrocytes and monocytes. Five out of 14 MBP specific T cell lines killed astrocytes in the presence of MBP. Nevertheless, all lines lysed blood derived monocytes. T cell lines that lysed astrocytes efficiently in the presence of MBP, recognized peptide aa 80-99/86-105 in context with HLA-DRB5 * 0101, peptide aa 50-69/61-83 in context with HLA-DRB1 * 1501 and peptides aa 139-153, and aa 148-162 in context with HLA-DRB1 * 0101. There was no correlation of MBP-mediated lysis of astrocytes with TCR-Vbeta usage, HLA-restriction and the production of tumor-necrosis-factor-alpha (TNF-alpha), lymphotoxin (LT) and interferon-gamma (IFN-gamma). Different lysis of astrocytes, however, revealed a functional heterogeneity of MBP specific T cells, which was not observed by using monocytes as targets.

Challenging cytokine redundancy: inflammatory cell movement and clinical course of experimental autoimmune encephalomyelitis are normal in lymphotoxin-deficient, but not tumor necrosis factor-deficient, mice

Lymphotoxin (LT) is widely regarded as a proinflammatory cytokine with activities equivalent to tumor necrosis factor (TNF). The contribution of LT to experimental autoimmune encephalomyelitis (EAE) was examined using TNF/LTalpha-/- mice, TNF-/- mice, and a new LTalpha-/- line described here. All mice were generated directly in the C57BL/6 strain and used for the preparation of radiation bone marrow chimeras to reconstitute peripheral lymphoid organs and restore immunocompetence. This approach overcame the problems related to the lack of lymph nodes that results from LTalpha gene targeting. We show here that when LT is absent but TNF is present, EAE progresses normally. In contrast, when TNF is absent but LT is present, EAE is delayed in onset and inflammatory leukocytes fail to move normally into the central nervous system parenchyma, even at the peak of disease. In the absence of both cytokines, the clinical and histological picture is identical to that seen when TNF alone is deficient, including demyelination. Furthermore, the therapeutic inhibition of TNF and LTalpha with soluble TNF receptor in unmanipulated wild-type or TNF-/- mice exactly reproduces these outcomes. We conclude from these studies that TNF and LT are functionally distinct cytokines in vivo, and despite sharing common receptors, show no redundancy of function nor mutual compensation.

A 21 point unifying hypothesis on the etiology and treatment of multiple sclerosis

Multiple sclerosis (MS) is postulated to be a cell mediated autoimmune disease directed against central nervous system myelin components. Our understanding of the disease has been enhanced by a number of factors: 1) advances in our understanding of the immune system; 2) clinical trials which are beginning to identify treatments which can affect MS; 3) a better understanding of the clinical features of MS; and 4) advances in MRI imaging of the brain. Based on the current state of knowledge, this paper proposes a 21 point unifying hypothesis on the etiology and treatment of the disease. This hypothesis makes a series of assumptions, many of which are unproven, and is presented as a framework from which to investigate and treat the disease, not as a established biology. It is hypothesized that the underlying pathogenesis of MS is related to an inappropriate class of immune response against myelin antigens favoring proinflammatory Th1 versus anti-inflammatory Th2 or Th3 type responses. Environmental and genetic factors predispose toward MS by affecting the class of response and effectiveness of treatment is also related to how it impacts on this common final pathway. Because of epitope spreading, there is not one autoantigen involved in MS and the progressive form of MS differs immunologically from the relapsing remitting form. Viruses trigger and perpetuate MS, although MS is not related to a persistent viral infection. Because MS is a multifactorial disease, there are clinical and perhaps immunological subtypes of MS and a single type of treatment is unlikely to control the disease in all patients. Thus, there will be responders and non-responders to each effective therapy and ultimately combination therapy will be required to cure the disease.

Multiple sclerosis: the frequency of allelic forms of tumor necrosis factor and lymphotoxin-alpha

The cytokines LTa and TNF have been implicated as major mediators of tissue injury in multiple sclerosis (MS). In this study we have assessed the frequency of specific polymorphisms for these genes in MS (n = 53) and controls (n = 81) using a highly sensitive, two stage nested polymerase chain reaction (PCR), with the second stage using mutation-specific primers. Genomic DNA was extracted from blood cells and the results confirmed by direct dideoxy chain termination sequencing. The frequency of the -308 G to A mutation in the TNF promoter region in normal controls was 15% and in MS was 24%. For LTa gene the exon 3 polymorphism allele A was detected in 36% of controls and 34% of the MS patients. In MS, the combined genotype TNF G + A and LTa C + C was present 6 times more frequently (12%) than in controls (2%), and patients with this genotype showed the highest EDSS scores. We found the TNF and LTa polymorphisms to occur independently from the HLA class II DR2 allele distribution in MS. Whilst the G - A polymorphism in TNF gene promoter has been studied previously in MS, with conflicting results, this is the first study that has addressed the exon 3 polymorphism in LTa in MS. The results indicate that this polymorphism is not linked with the higher genetic predisposition for MS, but that combined TNF G + A and LTa C + C genotype might contribute to development of the disease.

Cytokines, signal transduction, and inflammatory demyelination: review and hypothesis

The mechanism of focal demyelination in multiple sclerosis has been a long-standing enigma of this disorder. Cytokines, a diverse family of signalling molecules, are viewed as potential mediators of the process based on clinical observations and studies with animal models and tissue/cell culture systems. Myelin and oligodendrocyte (OL) destruction occur in cultured preparations subjected to cytokines such as tumor necrosis factor-alpha (TNF alpha) and lymphotoxin (LT). Many studies have shown these and other cytokines to be elevated at lesion sites and in the CSF of multiple sclerosis (MS) patients, with similar findings in animal models. Some variability in the nature of MS lesion formation has been reported, both OLs and myelin being primary targets. To account for myelin destruction in the presence of apparently functional OLs we hypothesize that cytokines such as TNF alpha and LT alpha contribute to myelin damage through triggering of specific reactions within the myelin sheath. We further propose that neutral sphingomyelinase (SMase) is one such enzyme, two forms of which have been detected in purified myelin. An additional event is accumulation of cholesterol ester, apparently a downstream consequence of cytokine-induced SMase. The resulting lipid changes are viewed as potentially destabilizing to myelin, which may render it more vulnerable to attack by invading and resident phagocytes.

Increased serum levels of soluble CD95 (APO-1/Fas) in relapsing-remitting multiple sclerosis

CD95/CD95 ligand interactions are critically involved in the negative regulation of peripheral T-cell responses. Here, we report that serum levels of soluble CD95 are significantly elevated in patients with relapsing remitting multiple sclerosis. In a transectional study, CD95 levels did not correlate with clinical disability or lesion formation on magnetic resonance imaging. Longitudinally, Expanded Disability Status Scale changes were associated with high CD95 levels. Interferon-beta (IFNbeta) treatment led to an initial increase and subsequent decline of serum CD95 levels. Interestingly, patients generating neutralizing antibodies to the drug had significantly higher baseline CD95 levels before IFNbeta treatment than those without neutralizing antibodies.

CD95 expression and CD95-mediated apoptosis of T cells in multiple sclerosis. No differences from normal individuals and no relation to HLA-DR2

CD95-mediated apoptosis is a potent endogenous pathway of T cell elimination that has been suggested to be altered in multiple sclerosis (MS). MS is associated with the HLA-DR2, Dw2, DQ6 HLA class II haplotype. We have previously reported that T cell lines from HLA-DR2-positive individuals show enhanced production of tumor necrosis factor (TNF), a cytokine homologous to CD95 ligand, in response to specific antigen. Here we have studied CD95 expression and susceptibility to CD95-mediated apoptosis in peripheral blood mononuclear cells (PBMC) and activated T cells of 20 healthy individuals and 20 MS patients, half of whom were HLA-DR2-positive. MS patients did not differ from healthy individuals in either parameter. There was also no difference in CD95 expression or CD95-mediated apoptosis when MS patients and healthy individuals were grouped and compared according to HLA-DR status. These data reveal no differential regulation of PBMC/T cell apoptosis induced by CD95 receptor ligation in MS and show no impact of HLA-DR2 status on PBMC/T cell susceptibility to the same apoptotic stimulus. However, to assess the contribution of T cell apoptosis to the pathogenesis of MS further studies on other details of the complex system leading to T cell apoptosis are required.

Human recombinant interferon-beta influences T helper subset differentiation by regulating cytokine secretion pattern and expression of homing receptors

Type I interferons (IFN) are important regulators of both innate and acquired immunity. We have used an in vitro system of human CD4+ T cell differentiation to determine how IFN-beta influences development of T helper (Th) subsets and homing receptor expression. IFN-beta promoted differentiation of CD4+ T cells that produce low levels of both IFN-gamma and lymphotoxin compared to interleukin (IL)-12-derived Th1 CD4+ T cells. IFN-beta inhibited production of Th2 cytokines (IL-5 and IL-13) and augmented IL-12-mediated IL-10 secretion. In addition, IFN-beta significantly enhanced L-selection expression on CD4+ T cells and synergized with IL-12 to induce expression of cutaneous lymphocyte-associated antigen (CLA). This Th1 L-selectin+, CLA+ phenotype is characteristic of T cells found in normal human skin and suggests a role for type I IFN in the regulation of Th subset differentiation and tissue-specific homing receptors.

Cytokine profile of myelin basic protein-reactive T cells in multiple sclerosis and healthy individuals

Myelin basic protein (MBP)-reactive T cells have been implicated in the autoimmune pathogenesis of multiple sclerosis (MS). In this study, we examined the cytokine profile of 531 primary MBP-reactive T-cell lines and 72 independently established clones from 32 patients with MS and 18 healthy controls (NS) by using highly sensitive enzyme-linked immunosorbent assays. An increased number of primary T-cell lines producing interferon-gamma (IFN gamma) and/or interleukin-4 (IL-4) in response to MBP were found in patients with MS compared with controls. No distinct Th1 or Th2 subtypes could be demonstrated among the MBP-reactive clones. IL-4 was more frequently observed among MS-derived clones. Clones derived from MS patients produced increased levels of IL-2, IL-4, tumor necrosis factor-alpha (TNF alpha), IFN gamma, and IL-10, but not IL-6. It is interesting that MBP-reactive T cells from MS patients expressing the disease-associated HLA-DRB1*15 allele produced increased quantities of TNF alpha, a cytokine suggested to play an important role in inflammation and demyelination. When challenged with either MBP or a bacterial superantigen, the clones expressed similar levels of the proinflammatory cytokine IFN gamma. Our study suggests a functional difference in T-cell responses to MBP in patients with MS compared with healthy individuals, and provides further insights into the role of MBP-reactive T cells and their cytokine profile in the inflammatory processes of MS.

Tumor Necrosis Factor Constellation Polymorphism and Clozapine-Induced Agranulocytosis in Two Different Ethnic Groups

Genes of the major histocompatibility complex (MHC) are associated with susceptibility to different immune and nonimmune mediated diseases. We had reported that the drug adverse reaction, clozapine-induced agranulocytosis (CA), is associated with different HLA types and HSP70 variants in Ashkenazi Jewish and non-Jewish patients, suggesting that a gene within the MHC region is associated with CA. This study was designed to find common genetic markers for this disorder in both ethnic groups. The tumor necrosis factor (TNF ) microsatellites d3 and b4 were found in higher frequencies in both Jewish and nonJewish patients: 51 of 66 (77%) and 48 of 66 (57%), respectively. Comparisons of these frequencies with those of controls, 28 of 66 (42%) and 18 of 66 (27%), were statistically significant (corrected P value = .001 for the d3 allele and .0005 for the b4 allele). On the other hand, the TNF microsatellite b5 was underrepresented in the group of patients, 9 of 66 (14%), when compared with the control subjects, 43 of 66 (65%) (corrected P value = .0005), probably related to protection from CA. Our results show a strong association of some genetic variants of the TNF loci with susceptibility to CA in two different ethnic groups suggesting involvement of TNF and/or associated gene(s) products in the pathogenesis of this hematologic-drug adverse reaction.

Immunologically induced electrophysiological dysfunction: implications for inflammatory diseases of the CNS and PNS

During inflammation of the central or peripheral nervous system, a high number of immunologically active molecules, including bacterial or viral products as well as host-derived cytokines, are released. Patients suffering from inflammatory CNS or PNS diseases often develop transient symptoms with a rapid recovery, which obviously cannot be accounted for by immunologically induced tissue damage. These observations led to the hypothesis that immunologically active molecules can affect directly the electrophysiological functions of neurons and glial cells. Evidence for this hypothesis came from in vitro studies showing that cytokines, such as interleukins or tumor necrosis factors, arachidonic acid and its metabolites, interfere with electrophysiological properties of neurons or glial cells. These molecules affect ion currents, intracellular Ca2+ homeostasis, membrane potentials, and suppress or enhance the induction and maintenance of long-term potentiation. Similarly, virus proteins from human immunodeficiency virus type I were found to alter intracellular Ca2+ concentrations of neurons and astrocytes by modulating either transmitter receptors and channels or membrane transporters. Cerebrospinal fluid from MS patients contains factors which increase Na+ current inactivation and thereby reduce neuronal excitability. Immunoglobulins in sera of patients suffering from multifocal motor neuropathy and from acquired neuromyotonia interfere with nerve fibers, inducing alterations of conduction. Increased knowledge of these mechanisms will help to explain the pathogenesis of neurological symptoms and may provide a rationale for new therapeutic strategies.

Interleukin-12 and tumor necrosis factor-alpha levels in cerebrospinal fluid of multiple sclerosis patients

Concentrations of interleukin (IL)-12 and tumor necrosis factor-alpha (TNF-alpha) in cerebrospinal fluid (CSF) were measured in patients with multiple sclerosis (MS) and control patients with non-inflammatory neurological diseases (NIND) by an enzyme-linked immunosorbent assay. TNF-alpha was detectable in the CSF of 60% of the patients with active MS, none of those with inactive MS and 29% of patients with NIND. CSF concentrations of TNF-alpha correlated with the degree of disability in MS patients (P < 0.05). Detectable levels of IL-12 were found in 10% of the MS CSF samples and 18% of NIND CSF samples. There was a significant relationship between CSF concentrations of IL-12 and those of TNF-alpha in MS patients (P < 0.05); no relationship was observed between the presence of IL-12 and disease activity or severity. These findings further stress the involvement of T helper 1 type-response within the central nervous system in MS.

TNF-alpha promoter polymorphisms, production and susceptibility to multiple sclerosis in different groups of patients

TNF-alpha production in whole blood cultures upon stimulation with LPS was determined in 179 individuals from 61 families in order to characterise the magnitude of inherited differences in TNF-alpha production. The three families characterised by highest TNF production showed 7.1 +/- 0.3 ng TNF/ml upon culture with 10 ng LPS and 10.2 +/- 0.2 ng TNF/ml upon culture with 1000 ng LPS. in contrast to the three families characterised by the lowest TNF production that showed a production of 1.6 +/- 0.1 ng TNF upon culture with 10 ng and 2.5 +/- 0.2 ng/ml upon culture with 1000 ng LPS/ml. This difference could not be attributed to the promoter polymorphisms -308 G to A. -238 G to A or -376 G to A, although the -238 GA donors produced 2.1 +/- 0.9 ng TNF upon culture with 10 ng endotoxin compared to 3.2 +/- 2.2 ng TNF for the -238 GG donors. In line with these results the frequency of the -238 GG genotype was increased in hospitalized MS patients in a nursing home (100% 238GG, n = 57) compared to MS patients in an outpatient's clinic (94% 238GG, n = 98) or Dutch controls (90% 238GG, n = 180). These results suggest that the -238 GG genotype is differently distributed in hospitalized MS patients in a nursing home.

TNF and related molecules: trends in neuroscience and clinical applications

A clear message to emerge from the recent 6th International TNF Congress is that TNF-alpha, LT-alpha and possibly other TNF family members, are important integral mediators of the CNS stress response to threatened homeostasis and that either excessive or insufficient TNF-alpha production can have significant consequences upon correct CNS functioning. Experimental data are particularly relevant in light of recent evidence which shows some linkage between polymorphisms in the human TNF-alpha/LT-alpha locus and susceptibility to CNS infection and thus highlight such cytokine pathways as promising therapeutic targets for the management of certain CNS diseases. Judging by the significant advances that have been made recently in the field of cytokine neurobiology, and the currently explosive development of transgenic and gene mutant mouse models with which to probe the cellular and molecular mechanisms of TNF-alpha and LT-alpha action within the CNS, we can look forward to shortly understanding more precisely the important and diverse roles that these cytokines play in CNS health and disease.

Pathogenesis of immune-mediated demyelination in the CNS

Collective evidence from studies in the animal model experimental autoimmune encephalomyelitis and pathological and immunological studies on MS patients suggest that this most common inflammatory demyelinating disorder of the central nervous system results from primarily T-lymphocyte driven aberrant immune responses to a number of myelin and possibly non-myelin antigens. These include MBP, PLP, MOG, MAG, CNP and S 100. Autoreactive T-cells reactive with these antigens circulate in blood and upon activation can travel across the blood-brain-barrier to initiate a local immunoflammatory response provided they encounter a microglial cell that displays antigenic epitopes in the context of MHC class II gene products and accessory molecules. Demyelination probably results from antibody-induced complement activation. Repeated inflammatory episodes eventually exhaust the reparative capacities of oligodendrocytes and damage axons. As the disease evolves, an initialy focussed immune response may diversify due to a process termed epitope spreading. The initial event of T lymphocyte activation remains elusive, but molecular mimicry, cross-recognition of structures shared between microbes and myelin, appears to be crucial.

Tumor necrosis factor (TNF) microsatellite haplotypes in relation to extended haplotypes, susceptibility to diseases associated with the major histocompatibility complex and TNF secretion

TNFabc microsatellite haplotypes were determined on normal, type I diabetes and multiple sclerosis Caucasian MHC haplotypes in family studies. Although independent examples of conserved extended haplotypes usually had the same TNFabc haplotypes, there were a number of exceptions, suggesting that these loci are more mutable than most loci in the human MHC. Some TNFabc haplotypes were characteristic of only one extended haplotype, whereas others were shared by several different extended haplotypes. From the analysis of TNFabc on extended haplotype fragments, and assuming that the fragments arose by ancient homologous crossing over, it was possible to "map" TNF and how that it was somewhat closer to HLA-B than the complement region, corresponding to the physical map of this region. TNF haplotype associations with type I diabetes and multiple sclerosis were attributable to the known extended haplotype associations of these diseases. There was also a trend for higher TNF-alpha secretion by peripheral blood mononuclear cells from individuals homozygous for [HLA-B8, SC01, DR3] than from individuals homozygous for [HLA-B7, SC31, DR2].