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Biomedical subjects

R Hohlfeld

Publications and source records attributed to R Hohlfeld.

At least 145 records · Page 8Linked to original sources
PubMed1990

Lysis of myotubes by alloreactive cytotoxic T cells and natural killer cells. Relevance to myoblast transplantation.

The aim of this study was to investigate the susceptibility of human myotubes to lysis by the two major types of cytotoxic effector cells, CD3+CD8+ cytotoxic T cells (CTL) and CD16+CD56+ natural killer (NK) cells. The myoblasts preparations used as target cells were greater than 90% pure as assessed by immunostaining with the Leu19 monoclonal antibody (MAb) that cross-reacts with the neural cell adhesion molecule N-CAM. Allospecific CTL lines were generated from mixed lymphocyte cultures, and freshly isolated allogeneic and autologous peripheral blood cells were used as a source of NK cells. The cytotoxicity was observed under phase optics and by immunoelectron microscopy, and was quantitated with a chromium release assay. Myotubes were efficiently killed by allospecific CTL and by autologous and allogeneic NK cells. The killing by CTL was inhibited with an anti-class I HLA MAb, and the killing by NK cells was inhibited by depleting peripheral blood cells of CD16+ cells with anti-CD16 MAb and complement. The results have important implications for myoblast transplantation, an experimental therapy of muscular dystrophy.

Cells, Cultured↗
PubMed1990

Induction of HLA-DR expression on human myoblasts with interferon-gamma.

Myoblast transplantation is an experimental therapy that may be useful in hereditary muscle diseases. One obstacle to this approach is immune rejection. We evaluated human myoblasts and myotubes for surface expression of HLA class I and II histocompatibility antigens. The myoblast preparations, cultured from muscle biopsy specimens, were more than 95% pure as assessed by immunostaining with the Leu19 monoclonal antibody that reacts with human myoblasts and regenerating muscle fibers. Myoblasts and myotubes constitutively expressed HLA-class I but not HLA-class II molecules. However, HLA-class II expression was induced on mononucleated myoblasts after culture for 5 days in the presence of recombinant human interferon-gamma. The results indicate that transplanted myoblasts can be rejected because of histoincompatibility at the HLA-class I and HLA class II locus. Furthermore, an aberrant expression of HLA-class II antigen on myoblasts in vivo may play a role in the pathogenesis of autoimmune muscle disorders.

Autoimmune Diseases↗
PubMed1989

Neurological autoimmune disease and the trimolecular complex of T-lymphocytes.

T-lymphocytes recognize antigen in a trimolecular complex: The T-cell receptor binds to a processed fragment of antigen that itself is bound to a major histocompatibility complex (MHC) molecule on the surface of an antigen-presenting cell. The trimolecular complex controls antigen-specific T-cell activation in normal and abnormal immune reactions. Recent progress in myasthenia gravis (MG) and experimental autoimmune encephalomyelitis (EAE) exemplifies this, leading to the following conclusions: (1) Autoimmune T cells may act by interfering with immunoregulation (as in MG) or by directly mediating autoimmune damage (as in EAE), or both. (2) In both diseases, the autoimmune T cells are clonally heterogeneous but recognize only a limited number of epitopes on the autoantigen (acetylcholine receptor in MG; myelin basic protein in EAE). Many of these epitopes can be defined as short peptide fragments of antigen, bound to a particular type of MHC molecule. (3) The MHC determines which peptides are recognized by autoimmune T cells in a given patient or inbred animal strain. (4) The discovery of the limited repertoire of autoimmune T cells has allowed considerable progress in the immunotherapy of EAE, using either monoclonal antibodies or cytotoxic T cells directed against clonotypic determinants on the autoaggressive T cells. (5) One obstacle to this approach in human disease is the polymorphism of the MHC in the species and the commensurate heterogeneity of autoimmune T cells.

Autoimmune Diseases↗
PubMed1989

Analysis of immunoglobulin and T cell receptor gene rearrangements in the thymus of myasthenia gravis patients.

The thymus is an important site of sensitization of autoreactive B and T lymphocytes in myasthenia gravis (MG). We have investigated clonal diversity of B or T cells in the thymus of patients with MG by Southern blot experiments using probes specific for immunoglobulin heavy (IgH) and light chain (IgL) genes and for T cell receptor (TCR) beta- and gamma-chain genes. This method allows to detect individual clones of B or T cells if they represent at least 1% of the total cell population. We investigated thymus glands from 14 patients who underwent thymectomy. Single rearranged fragments could be demonstrated with a TCR gamma-specific probe in DNAs from both normal donors and MG patients. TCR beta gene rearrangements occurred mainly in the C beta 1 region. However, single rearranged bands could not be detected with either TCR beta, JH or with J kappa specific probes. Thus any single autoimmune B and T cell clone present in the myasthenic thymus represents presumably less than 1% of all thymocytes.

Blotting, Southern↗
PubMed1988

Amphipathic segment of the nicotinic receptor alpha subunit contains epitopes recognized by T lymphocytes in myasthenia gravis.

Autoimmune helper T lymphocytes were selected from the blood of two myasthenic patients of different HLA-DR type, using acetylcholine receptor (AChR) from Torpedo californica. These polyclonal T cell lines were tested for reactivity with three synthetic peptides corresponding to the NH2-terminal region of the human AChR alpha subunit. This segment is a good candidate for T cell epitopes since it has a propensity to form an amphipathic alpha helix. The peptides elicited 10-30% of the response induced by native Torpedo AChR. Different peptides were recognized by the autoreactive T cells of the two patients. These results suggest that the NH2-terminal region of the AChR alpha chain contains T cell-stimulating epitopes, and that the T cell autoimmune response in myasthenia gravis, like the B cell response, is heterogeneous.

Adult↗
PubMed1988

Azathioprine toxicity during long-term immunosuppression of generalized myasthenia gravis.

In this uncontrolled study, 104 patients with generalized myasthenia gravis treated with azathioprine for a median period of 29 months (range, 1 month to 12 years) were surveyed for possible adverse reactions. These occurred in 36 patients (35%) in the following order of frequency: hematologic (18%), gastrointestinal (13%), infectious diseases (13%), and elevation of liver enzymes (6%). No allergic skin reactions were observed. Azathioprine had to be discontinued temporarily in a total of 11 patients (11%) because of possible side effects. The cause of death in the nine patients who died during the period of observation (up to 12 years) was related to myasthenic crisis in two patients. In five patients, a malignant tumor was diagnosed (two carcinoma of the prostate, one ovarian carcinoma, one bronchial carcinoma, and one renal lymphoma) after 2.5 years, 6 months, 3 months, 5 years, and 6 years of treatment, respectively. A causal relationship seems unlikely in the first four cases, but cannot be excluded in the one case of late lymphoma.

Aged↗
PubMed1987

A reliable method for immunocytochemical characterization of CSF cells.

A technically convenient and reliable method for immunoenzymatic staining of cerebrospinal fluid (CSF) cells is described. Compared with immunofluorescence techniques this method has the advantage that the immunocytochemical preparations can be counterstained and stored indefinitely.

Antibodies, Monoclonal↗
PubMed1987

Human T-helper lymphocytes in myasthenia gravis recognize the nicotinic receptor alpha subunit.

Myasthenia gravis is a human disease caused by an autoimmune response against the nicotinic acetylcholine receptor (AcChoR). Since the molecular structure of AcChoR is well known, myasthenia gravis is an excellent system for studying the recognition of a complex membrane antigen in the human immune system. Human T-helper (TH) cell lines reactive to the AcChoR were isolated from four myasthenic patients by selection with native AcChoR from Torpedo californica. The selected TH cells could efficiently recognize native and fully denatured AcChoR. The vast majority of the TH-stimulating AcChoR epitopes were located on the denatured alpha subunit of AcChoR. Antibody competition experiments using a panel of rat anti-AcChoR monoclonal antibodies showed that 39-45% of the autoantibodies present in the sera of these same patients bound to the conformation-sensitive "main immunogenic region" (MIR), also located on the alpha subunit. However, AcChoR-induced stimulation of the T cells could not be inhibited with up to 20-fold molar excess of different rat anti-MIR monoclonal antibodies. These results suggest that the Torpedo AcChoR alpha subunit contains conformation-insensitive epitopes that play a role in the autosensitization of TH cells and that seem to be physically separated from the MIR. The specificity of the TH cell response may contribute to directing the B-cell response to other alpha-subunit determinants, such as the MIR itself.

Animals↗
PubMed1986

HLA-DQ beta-chain polymorphism linked to myasthenia gravis.

The HLA-DR3 haplotype is associated with increased risk of myasthenia gravis (MG) and a number of other autoimmune diseases, including insulin-dependent diabetes mellitus (IDDM), coeliac disease, and premature ovarian failure (POF). With a cDNA probe for a DQ beta gene, a 15 kb Hinc II restriction fragment has been demonstrated in genomic DNA from 7 of 16 HLA-DR3 patients with MG, 1 of 19 healthy DR3 controls, and none of 24 DR3 patients with IDDM, coeliac disease, or POF. The HLA-DQ polymorphism may be closely linked to a genetic locus regulating immune responsiveness to acetylcholine receptor and susceptibility to MG.

Celiac Disease↗
PubMed1986

Effector mechanisms in myasthenia gravis: end-plate function after passive transfer of IgG, Fab, and F(ab')2 hybrid molecules.

Using the quantitative ionophoresis technique and the mouse passive transfer model of myasthenia gravis, end-plate function was measured in mice transferred with myasthenic IgG, Fab, or F(ab')2 hybrid molecules prepared by recombination of one acetylcholine receptor (AChR) specific Fab and one Fab directed against irrelevant antigen. The Hill coefficient (a measure for the cooperativity between AChR subunits) and the apparent dissociation constant K for the ACh-AChR interaction were essentially unaltered after passive transfer of IgG or IgG fragments. In contrast, myasthenic IgG and Fab, but not control IgG or Fab, markedly reduced the mean number of end-plate channels. A similar effect was observed after passive transfer of F(ab')2 hybrid molecules. These results show that passive transfer of myasthenic IgG or IgG fragments leads to a quantitative reduction of ACh-controlled end-plate channels, whereas the function of the remaining receptors/channels remains unchanged. The results suggest further that cross-linking of AChR by divalent antibody may not be an absolute requirement for the reduction of AChR at the functional neuromuscular synapse.

Animals↗