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

The neurotoxic effect of cuprizone on oligodendrocytes depends on the presence of pro-inflammatory cytokines secreted by microglia

In order to further characterize the still unknown mechanism of cuprizone-induced demyelination, we investigated its effect on rat primary oligodendroglial cell cultures. Cell viability was not significantly affected by this treatment. However, when concentrations of IFNgamma and/or TNFalpha having no deleterious effects per se on cell viability were added together with cuprizone, cell viability decreased significantly. In mitochondria isolated from cuprizone-treated glial cells, we observed a marked decrease in the activities of the various complexes of the respiratory chain, indicating a disruption of mitochondrial function. An enhancement in oxidant production was also observed in cuprizone and/or TNFalpha-treated oligodendroglial cells. In in vivo experiments, inhibition of microglial activation with minocycline prevented cuprizone-induced demyelination. Based on the above-mentioned results we suggest that these microglial cells appear to have a very active role in cuprizone-induced oligodendroglial cell death and demyelination, through the production and secretion of pro-inflammatory cytokines.

Cytokine-induced cell death in human oligodendroglial cell lines: I. Synergistic effects of IFN-gamma and TNF-alpha on apoptosis

Multiple sclerosis is a chronic inflammatory disease of the central nervous system. Myelin and oligodendrocytes are considered the major targets of injury caused by a cell-mediated immune response. There is circumstantial evidence that proinflammatory cytokines like tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) could have disease-promoting roles in multiple sclerosis (MS). In the present study, the cytotoxic effects of IFN-gamma and TNF-alpha on the human oligodendroglial cell lines human oligodendroglioma (HOG) and MO3.13 were analyzed. When the oligodendroglial cell lines were cultured in the presence of IFN-gamma or TNF-alpha, apoptotic cell death was observed in both cell lines after >24 hr incubation. Apoptosis was evidenced by a decrease in cell viability, apoptotic changes in cell and nucleus morphology, and disruption of the membrane asymmetry. Our data show that TNF-alpha and IFN-gamma induce apoptosis in a dose-dependent fashion in both oligodendroglial cell lines and that their synergistic effect results in enhanced cell death. Understanding the regulation of cell death pathways in oligodendrocytes is critical for protecting myelin-producing cells and their associated axons during injury in patients with MS.

Serial analysis of cytokine mRNA profiles in whole blood samples from patients with early multiple sclerosis

In this pilot study, we serially determined the cytokine messenger RNA (mRNA) expression pattern in whole blood samples from 12 patients with clinical isolated syndrome suggestive of early multiple sclerosis (MS) using a new sensitive quantitative polymerase chain reaction (PCR) method. Significantly higher levels of tumor necrosis factor-alpha (TNF-alpha; x 5.1), interferon-gamma (IFN-gamma; x 4.8) and interleukin-10 (IL-10; x 5.6) mRNA were detected in MS patients at the time of a relapse compared to healthy controls. Treatment with i.v. methylprednisolone (MP) led to an increase of IL-4 mRNA and a significant decrease of IFN-gamma and TNF-alpha mRNA expression. In this cohort of clinically stable patients, proinflammatory cytokines remained low during the 1-year follow-up period. As several indications point to a cytokine dysregulation in MS, quantitative analysis of cytokine mRNA profiles in whole blood samples by real time PCR may be a useful immunological marker to monitor disease activity in future therapeutic trials in MS.

Modeling alternative binding registers of a minimal immunogenic peptide on two class II major histocompatibility complex (MHC II) molecules predicts polarized T-cell receptor (TCR) contact positions

Several major histocompatibility complex class II (MHC II) complexes with known minimal immunogenic peptides have now been solved by X-ray crystallography. Specificity pockets within the MHC II binding groove provide distinct peptide contacts that influence peptide conformation and define the binding register within different allelic MHC II molecules. Altering peptide ligands with respect to the residues that contact the T-cell receptor (TCR) can drastically change the nature of the ensuing immune response. Here, we provide an example of how MHC II (I-A) molecules may indirectly effect TCR contacts with a peptide and drive functionally distinct immune responses. We modeled the same immunogenic 12-amino acid peptide into the binding grooves of two allelic MHC II molecules linked to distinct cytokine responses against the peptide. Surprisingly, the favored conformation of the peptide in each molecule was distinct with respect to the exposure of the N- or C-terminus of the peptide above the MHC II binding groove. T-cell clones derived from each allelic MHC II genotype were found to be allele-restricted with respect to the recognition of these N- vs. C-terminal residues on the bound peptide. Taken together, these data suggest that MHC II alleles may influence T-cell functions by restricting TCR access to specific residues of the I-A-bound peptide. Thus, these data are of significance to diseases that display genetic linkage to specific MHC II alleles, e.g. type 1 diabetes and rheumatoid arthritis.

Inflammation, depressive symptomtology, and coronary artery disease

OBJECTIVE

Many patients feel exhausted or depressed before the onset of an acute coronary event, but little is known about the origin of these feelings. We tested the hypothesis that the depressive symptomatology is associated with a reactivation of latent viruses and inflammation of a coronary vessel.

METHODS

A blood sample was drawn and a biopsy sample was obtained from the coronary lesion of 15 exhausted and 15 nonexhausted patients treated with directional coronary angioplasty because of severe angina. Blood samples were analyzed to measure antibody titers against Chlamydia pneumoniae, cytomegalovirus, and the cytokines interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. The biopsy sample was analyzed for the presence of IL-1beta and TNF-alpha.

RESULTS

Exhausted/depressed patients had higher antibody titers against cytomegalovirus, higher levels of C. pneumoniae immunoglobulin G, and higher levels of IL-1beta and TNF-alpha. No associations between the mental state of a patient and cytokine mRNA in the biopsy sample were found.

CONCLUSIONS

The findings indicate that the mental state of angioplasty patients is positively associated with serological markers of inflammation. It remains to be seen whether the inflammation causes feelings of exhaustion, whether exhaustion and depression set the stage for inflammation, or whether existing feelings of exhaustion are amplified by the inflammation.

Cytokine secretion profile of myelin basic protein-specific T cells in multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system with a presumed autoimmune pathogenesis involving autoantigen-specific CD4+ T cells and cytokines. A similar frequency of T cells responding to myelin basic protein (MBP), a putative target in MS, has been observed in MS patients and controls. To dissect the differences between MBP-specific T cells in patients and controls, we have analyzed the cytokine secretion profile of such autoreactive T cells. MBP-specific T cell clones (TCC) were isolated from the peripheral blood of MS patients and controls by limiting dilution. Expression of mRNA for interferon-gamma (IFN-gamma), interleukin (IL)-4, IL-10, tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) was assessed by polymerase chain reaction whereas secretion of cytokine protein was measured by ELISA. MBP-specific TCC exhibited a heterogeneous cytokine secretion profile with clones displaying Th1, Th2 and Th0 phenotypes. A significant difference in the distribution of the cytokine profile was noted between MS patients and controls. Although the frequency of Th1 secreting MBP-reactive TCC was similar between MS patients and controls, stable MS patients had a significant association with the Th0 phenotype whereas healthy individuals were associated with the Th2 phenotype. In comparison to control TCC, MBP-specific TCC from MS patients secreted increased amounts of IFN-gamma, IL-4 and IL-10 and decreased quantities of TGF-beta. Thus, these studies suggest that there is a dysregulation in the balance between pro-inflammatory Th1 and anti-inflammatory Th2 cytokines in MS. It appears that the presence of Th1 secreting autoreactive T cells in healthy individuals may be counterbalanced by the presence of cells secreting Th2 cytokines and by the augmented production of the immunosuppressive cytokine TGF-beta, whereas in MS there is a decrease in these anti-inflammatory agents.

Preferential expansion of autoreactive T lymphocytes from the memory T-cell pool by IL-7

We have developed a new technique that allows us to quantify antigen-specific T cells, and to determine their functional phenotype and origin from naive versus memory populations. Using this methodology, we have characterized a total of 286 T-cell lines specific for myelin basic protein (MBP) and influenza hemagglutinin from 16 multiple sclerosis (MS) patients and nine healthy donors. Our data support the notion that MBP-specific T cells undergo in vivo activation in MS patients and indicate a presence of immune dysregulation that renders MS patients prone to develop autoimmunity. Our methodology offers a way to study antigen-specific T-cell characteristics as a surrogate marker in immunotherapy trials.

Developing antigen-specific therapies in multiple sclerosis: a tale of Tantalus or Ulysses?

Autoreactive T-cell responses directed to myelin proteins in the central nervous system are widely believed to be crucial in the pathology of multiple sclerosis (MS). However, effective ways of selectively targeting these T-cells in order to alter the clinical course of MS in a predictable manner has yet to be demonstrated. This review discusses two recent developments of crucial importance to the rational development of antigen-specific therapy in MS. The very idea of antigen-specific therapy in MS has long faced the challenge of determinant spreading, i.e., the development of novel autoimmune responses as the consequence of tissue damage. This phenomenon has led many to expect that in ongoing MS, many different pathogenic specificities would accumulate. Obviously, this would render antigen-specific therapy very difficult. Recent data now suggest that determinant spreading is most likely to be a transient phenomenon limited only to the first stages of tissue damage. A second development has changed our perspective on the specificity of individual T-cells and, thus, on the suitability of various ways to implement antigen-specific therapy. Evidence is rapidly accumulating that T-cell receptors are much more cross-reactive than previously assumed. This notion poses unexpected challenges to therapeutic approaches in MS that are based on selective targeting of autoreactive TCR. Vaccination with TCR peptides, administration of anti-TCR antibodies and development of therapeutically altered peptide ligands all depend on a significant level of predictability of pathogenic TCR. With such predictability now turning out to be much lower than was previously hoped, selective TCR-directed strategies for intervention may therefore turn out to be much less effective than anticipated. In the development of antigen-specific therapies, the use of whole protein tolerogens now seems to be the most promising route. Oral, intranasal or iv. administration of antigen remain viable options to re-establish selective tolerance that ought to be further developed for the benefit of MS patients.

The paradigm of Th1 and Th2 cytokines: its relevance to autoimmunity and allergy

In the past few years, considerable evidence has accumulated to suggest the existence of functionally polarized responses by the CD4+ T helper (Th)--and the CD8+ T cytotoxic (Tc)-cell subsets that depend on the cytokines they produce. The Th1 and Th2 cellular immune response provide a useful model for explaining not only the different types of protection, but also the pathogenic mechanisms of several immunopathological disorders. The factors responsible for the polarization of specific immune response into a predominant Th1 or Th2 profile have been extensively investigated in mice and humans. Evidence has accumulated from animal models to suggest that Th1-type lymphokines are involved in the genesis of organ-specific autoimmune diseases, such as experimental autoimmune uveitis, experimental allergic encephalomyelitis, or insulin-dependent diabetes mellitus. Accordingly, data so far available in human diseases favor a prevalent Th1 lymphokine profile in target organs of patients with organ-specific autoimmunity. By contrast, Th2-cell predominance was found in the skin of patients with chronic graft-versus host disease, progressive systemic sclerosis, systemic lupus erythematosus, and allergic diseases. The Th1/Th2 concept suggests that modulation of relative contribution of Th1- or Th2-type cytokines regulate the balance between protection and immunopathology, as well as the development and/or the severity of some immunologic disorders. In this review, we have discussed the paradigm of Th1 and Th2 cytokines in relation to autoimmunity and allergy.