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Biomedical subjects

R Hohlfeld

Publications and source records attributed to R Hohlfeld.

At least 55 records · Page 3Linked to original sources
PubMed2000

Clonal expansions of CD8(+) T cells dominate the T cell infiltrate in active multiple sclerosis lesions as shown by micromanipulation and single cell polymerase chain reaction.

Clonal composition and T cell receptor (TCR) repertoire of CD4(+) and CD8(+) T cells infiltrating actively demyelinating multiple sclerosis (MS) lesions were determined with unprecedented resolution at the level of single cells. Individual CD4(+) or CD8(+) T cells were isolated from frozen sections of lesional tissue by micromanipulation and subjected to single target amplification of TCR-beta gene rearrangements. This strategy allows the assignment of a TCR variable region (V region) sequence to the particular T cell from which it was amplified. Sequence analysis revealed that in both cases investigated, the majority of CD8(+) T cells belonged to few clones. One of these clones accounted for 35% of CD8(+) T cells in case 1. V region sequence comparison revealed signs of selection for common peptide specificities for some of the CD8(+) T cells in case 1. In both cases, the CD4(+) T cell population was more heterogeneous. Most CD4(+) and CD8(+) clones were represented in perivascular infiltrates as well as among parenchymal T cells. In case 2, two of the CD8(+) clones identified in brain tissue were also detected in peripheral blood. Investigation of the antigenic specificities of expanded clones may help to elucidate their functional properties.

Adult↗
PubMed2000

The neuroprotective effect of inflammation: implications for the therapy of multiple sclerosis.

Autoreactive T cells are a component of the normal immune system. It has been proposed that some of these autoreactive T cells even have a protective function. Recent studies support this notion by demonstrating that (a) myelin basic-protein (MBP-) specific T cells show neuroprotective effects in vivo, and (b) activated antigen-specific human T cells and other immune cells produce bioactive brain-derived neurotrophic factor (BDNF) in vitro. Furthermore, BDNF is expressed in different types of inflammatory cells in brain lesions of patients with acute disseminated leukoencephalopathy or multiple sclerosis. We postulate that the neuroprotective effect of T cells and other immune cells observed in vivo is at least partially mediated by BDNF and other neurotrophic factors. The concept of neuroprotective autoimmunity has obvious implications for the therapy of multiple sclerosis and other neuroimmunological diseases.

Brain-Derived Neurotrophic Factor↗
PubMed2000

Multiple sclerosis: comparison of copolymer-1- reactive T cell lines from treated and untreated subjects reveals cytokine shift from T helper 1 to T helper 2 cells.

Copolymer 1 (COP), a standardized mixture of synthetic polypeptides consisting of l-glutamic acid, l-lysine, l-alanine, and l-tyrosine, has beneficial effects in multiple sclerosis and experimental autoimmune encephalomyelitis. We selected a panel of 721 COP-reactive T cell lines (TCL) from the blood of COP-treated and untreated multiple sclerosis patients and from healthy donors by using the split-well cloning technique. All TCL selected with COP proliferated in response to COP but not to myelin basic protein (MBP). Conversely, 31 control TCL selected with MBP proliferated in response to MBP but not to COP. We used intracellular double-immunofluorescence flow cytometry for quantitative analysis of cytokine production (IL-4, IFN-gamma) by the TCL. The majority of the COP-reactive TCL from untreated multiple sclerosis patients and normal donors predominantly produced IFN-gamma and, accordingly, were classified as T helper 1 cells (TH1). In contrast, the majority of the COP-reactive TCL from COP-treated patients predominantly (but not exclusively) produced IL-4-i.e., were TH2 (P < 0.05 as assessed by using a suitable preference intensity index). Longitudinal analyses revealed that the cytokine profile of COP-reactive TCL tends to shift from TH1 to TH2 during treatment. Interestingly, although there was no proliferative cross-reaction, about 10% of the COP-reactive TCL responded to MBP by secretion of small amounts of IL-4 or IFN-gamma, depending on the cytokine profile of the TCL. These results are consistent with a protective effect of COP-reactive TH2 cells. It is hypothesized that these cells are activated by COP in the periphery, migrate into the central nervous system, and produce immunomodulatory cytokines after local recognition of MBP.

Adolescent↗
PubMed2000

T cell transformation with Herpesvirus saimiri: a tool for neuroimmunological research.

The finite life span of human T lymphocytes and their requirement of regular restimulation frequently limit human T cell studies. Once infected with H. saimiri, however, human and monkey T cells are transformed to stable growth without the need for further restimulation. H. saimiri persists in human growth-transformed T cells episomally and only a few viral genes are expressed. The release of infectious virus from transformed human T cells has not been observed. H. saimiri-transformed T cells have the phenotype of mature activated CD4+ or CD8+ T cells. Transformed T cells retain a structurally and functionally intact T cell receptor and respond specifically to recognition of their antigen. They produce Th1-like cytokines, provide B cell help, can be triggered to become cytotoxic, and are sensitive to a variety of apoptosis-inducing treatments. While H. saimiri-transformed T cells resemble native T cells in numerous aspects, their reactivity to CD2 is strikingly different: Native T cells are activated via CD2 by certain pairs of mAbs, but not by the mere binding of CD2 to its ligand CD58. In contrast, H. saimiri-transformed T cells are activated by a single crosslinked anti-CD2 mAb and also by interaction with CD58-bearing cells.

Apoptosis↗
PubMed2000

[Multiple sclerosis. Current review of failed and discontinued clinical trials of drug treatment].

Recent immunobiological findings together with advances in biotechnology, ameliorations in clinical trial design, and MRI developments have led to a variety of therapeutical approaches in multiple sclerosis (MS). However, in contrast to successfully introduced new treatments, a number of therapeutical failures exist as well: despite impressive data from animal models, convincing concepts, and promising phase I/II studies, some investigated drugs and strategies showed no positive effects in clinical trials, or trials had to be terminated because of unexpected side effects. This article provides an overview of clinical studies that have failed or been abandoned for other reasons. Tumor necrosis factor (TNF) alpha-antagonists which have led to negative effects in two studies (Lenercept, Infliximab) are discussed in detail. These results raise critical questions concerning the hypothetical pathogenesis of MS lesions and the value of MRI in the assessment of clinically relevant therapeutic drug effects. In addition to a description of the immunobiological background, studies on the immunosuppressive agents linomide, deoxyspergualin, sulfasalazine and cladribine, trials for the cytokines interleukin-10 and TGF-beta 2, the studies on remyelination by intravenous immunoglobulins (IVIg), oral tolerance, and extracorporeal photopheresis are discussed.

Adjuvants, Immunologic↗
PubMed2000

Repertoire dynamics of autoreactive T cells in multiple sclerosis patients and healthy subjects: epitope spreading versus clonal persistence.

Autoantigen-specific T-lymphocytes are present in patients with autoimmune disease and in normal subjects. Little is currently known about the temporal variation (dynamics) of the immune repertoire of these autoreactive T cells. We analysed the long-term variation of the immune repertoire of T cells specific for myelin basic protein (MBP) in five untreated patients with multiple sclerosis and four normal control subjects over a mean observation period of 6 years. MBP-specific CD4(+) T-cell lines were selected with purified human MBP, and their epitope specificity was mapped with overlapping synthetic peptides. Three distinct patterns of repertoire development were observed. (i) Two patients and three control subjects maintained a broad epitope response with fluctuations over time. (ii) Two patients initially showed a focused response that broadened over the course of 6 years; this finding could be described as intramolecular epitope spreading. (iii) In one patient and one control subject, a strikingly focused response, which was directed to a cluster of nested epitopes in the MBP region 83-102, persisted over time. T-cell receptor Vbeta sequence analysis allowed us to trace individual clones of MBP-specific T cells for up to 7 years in the peripheral circulation in four of the five patients and three of the four controls, suggesting that the long-term persistence of MBP-specific T-cell clones is a common feature of the T-cell repertoire not unique to multiple sclerosis. The persisting MBP-specific T-cell clones were not detectable in the blood of one of the patients by complementarity-determining region (CDR)-3 spectratyping, indicating that their frequency does not exceed 1 in 5000 T cells. The temporal characteristics of the MBP-specific T-cell repertoire described here are relevant to therapeutic strategies targeting autoantigen-specific T cells in multiple sclerosis and other autoimmune diseases.

Adult↗
PubMed2000

Muscle fibers in inflammatory myopathies and cultured myoblasts express the nonclassical major histocompatibility antigen HLA-G.

We demonstrate that HLA-G, a nonclassical major histocompatibility complex class I antigen, is expressed in muscle fibers in various inflammatory myopathies. Further, interferon-gamma induces surface expression and upregulation of mRNA transcripts corresponding to different isoforms of HLA-G in myoblasts cultured from control subjects and patients. HLA-G may have important immunological functions in inflammatory myopathies and other local immune reactions as they occur during vaccination, myoblast transplantation, and gene therapy.

Cells, Cultured↗
PubMed1999

Multiple sclerosis: side effects of interferon beta therapy and their management.

Article abstract-Interferon beta (IFNbeta) reduces the relapse rate, disease activity as measured by serial MRI scanning, and disease progression of MS. Therapy with IFNbeta may be associated with a number of adverse reactions. Relatively frequent side effects include flu-like symptoms, transient laboratory abnormalities, menstrual disorders, and increased spasticity. Dermal injection site reactions occur after subcutaneous application of IFNbeta-1b and IFNbeta-1a. Possible side effects of IFNbeta include various autoimmune reactions, capillary leak syndrome, anaphylactic shock, thrombotic-thrombocytopenic purpura, insomnia, headache, alopecia, and depression. We discuss the mechanisms and management of the different side effects of IFNbeta.

Affect↗
PubMed1999

Therapeutic strategies in multiple sclerosis. I. Immunotherapy.

This review first addresses several general aspects of the immunotherapy of multiple sclerosis. Next, two approved immunomodulatory treatments, interferon-beta and copolymer-1 (glatiramer acetate), are reviewed in more detail. Finally, other immunosuppressive therapies and experimental strategies are briefly discussed.

Coat Protein Complex I↗
PubMed1999

Activated human T cells, B cells, and monocytes produce brain-derived neurotrophic factor in vitro and in inflammatory brain lesions: a neuroprotective role of inflammation?

Brain-derived neurotrophic factor (BDNF) has potent effects on neuronal survival and plasticity during development and after injury. In the nervous system, neurons are considered the major cellular source of BDNF. We demonstrate here that in addition, activated human T cells, B cells, and monocytes secrete bioactive BDNF in vitro. Notably, in T helper (Th)1- and Th2-type CD4(+) T cell lines specific for myelin autoantigens such as myelin basic protein or myelin oligodendrocyte glycoprotein, BDNF production is increased upon antigen stimulation. The BDNF secreted by immune cells is bioactive, as it supports neuronal survival in vitro. Using anti-BDNF monoclonal antibody and polyclonal antiserum, BDNF immunoreactivity is demonstrable in inflammatory infiltrates in the brain of patients with acute disseminated encephalitis and multiple sclerosis. The results raise the possibility that in the nervous system, inflammatory infiltrates have a neuroprotective effect, which may limit the success of nonselective immunotherapies.

Autoantigens↗
PubMed1999

Myasthenia gravis: selective enrichment of antiacetylcholine receptor antibody production in untransformed human B cell cultures.

B cells producing antibodies against the acetylcholine receptor (AchR) play a central role in the pathogenesis of myasthenia gravis (MG). Although anti-AchR autoantibodies have been studied extensively, not much is known about autoimmune B cells and their antigen-driven activation. This has mainly been due to difficulties in establishing and maintaining untransformed antigen-specific B cells in vitro. In this study, we show that highly enriched B cells from peripheral blood and thymus of MG patients can be maintained in culture over a period of 4 weeks when grown on the AchR-expressing rhabdomyosarcoma cell line TE671 together with an anti-CD40 stimulus and lymphokines. Anti-AchR antibody secretion could be detected in the majority of B cell cultures on TE671 cells up to 4 weeks. In contrast, B cells cultured on CDw32-transfected L cells binding anti-CD40 antibodies (the CD40 system) produced only small amounts of anti-AchR antibodies at single time points, whereas the overall IgG production was higher than on TE671 cells. The expression of the relevant autoantigen on the adherent cell line in addition to other growth stimuli could account for this difference and may provide a useful tool for investigating antigen-dependent B cell activation in MG and other B cell-mediated autoimmune conditions.

Animals↗
PubMed1999

['Fatigue' in multiple sclerosis].

Fatigue is a common symptom in patients with multiple sclerosis. Rapid exhaustion and reduced exercise tolerance leads to difficulties in maintaining a normal daily life for many patients. Regular resting and short breaks can help to compensate this to a certain degree. The pathophysiology of fatigue is currently unknown. Damage of specific neuroanatomic regions or a more generalized effect of inflammatory mediators in the central nervous system could be the causes of fatigue. Some drugs (e.g. amantadine) have proven effective in therapy of fatigue. Recent therapeutic approaches have begun using aminopyridines (4-aminopyridine, 3,4-diaminopyridine). These two substances are thought to improve nerve conduction, but there might be a central stimulatory effect as well. Overdosage leads to an elevated risk of epileptic seizures and confusion.

Amantadine↗