Biomedical subjects

H Link

Publications and source records attributed to H Link.

At least 343 records · Page 19Linked to original sources

PubMed1992

Myasthenia gravis: T and B cell reactivities to the beta-bungarotoxin binding protein presynaptic membrane receptor.

Antibodies against acetylcholine receptor (AChR) can be detected in most patients with myasthenia gravis (MG) and are considered to be involved in the immunopathogenesis of this disease. AChR are isolated from crude receptor preparations by binding to alpha-bungarotoxin (alpha-BuTx). Patients with MG have also antibodies against a second protein tentatively named presynaptic membrane receptor (PsmR), which has been isolated from crude receptor utilizing beta-bungarotoxin (beta-BuTx). PsmR could represent another antigen besides AChR relevant for the development of MG. We have now evaluated the T cell reactivity to PsmR in MG and controls by analysing the frequencies of cells which in response to PsmR in short-term cultures secreted interferon-gamma (IFN-gamma). The B cell response to PsmR was analysed in parallel by counting cells secreting anti-PsmR antibodies. Most patients with MG had PsmR reactive T cell in blood with a median number of about 1 per 44,000 mononuclear cells. Cells secreting anti-PsmR antibodies belonging to the IgG and IgA isotypes, less frequently of the IgM isotype were detected in most MG patients. A positive correlation was found between T cells reactive with PsmR and anti-PsmR IgG antibody secreting cells. PsmR reactive T and B cells were also detected in control patients, but at much lower numbers. Our results indicate that MG is accompanied by T as well as B cell responses to PsmR, in addition to the previously recognized responses to AChR. It remains to be shown whether these PsmR reactivities are of pathogenetic importance in MG.

Adult↗

PubMed1992

Increased systemic B- and T-lymphocyte responses in hereditary motor and sensory neuropathy (HMSN I).

Immune mechanisms of possible importance for the development and maintenance of peripheral nerve myelin breakdown in HMSN I were analysed by measuring B- and T-cell activation in blood, bone marrow and cerebrospinal fluid. Patients with polyneuropathies of other etiologies served as one control group and patients with tension headache as another. Flow cytometry of blood and bone marrow mononuclear cells revealed that an increased number of CD3+, CD4+ and CD4- CD8- T-cells expressed a late stage activation marker (Ta1). Analysis of T-cells primed for myelin antigens, by studies of IFN-gamma secretion in response to antigen in vitro, showed that both HMSN I and other polyneuropathy patients had low (but significant) numbers of T-cells recognizing whole PNS-myelin. Increased numbers of IgG- and IgM-producing cells were found in blood and bone marrow in the HMSN I patients. Patients with both HMSN I and the other polyneuropathies had few cells in peripheral blood and in bone marrow producing antibodies binding to P2, MAG and MBP in a solid phase immunospot assay. Many cells in the cerebrospinal fluid produced antibodies against MAG. Thus, there was a strong general activation of B- and T-cells in HMSN I while the immunity directed toward peripheral nerve was only slightly elevated. It is an open question if this immune activation is related to the primary gene defect or a secondary event to the nerve damage. The pathogenetic importance of the immune response in maintaining the nerve damage in HMSN I is unclear.

Adult↗

PubMed1992

Virus-reactive and autoreactive T cells are accumulated in cerebrospinal fluid in multiple sclerosis.

Elevated numbers of B cells--plasma cells secreting antibodies to measles and mumps virus, and to myelin associated glycoprotein (MAG), one of several putative myelin autoantigens--have previously been reported in cerebrospinal fluid (CSF) from patients with multiple sclerosis (MS), while it is unknown if corresponding T cell reactivities occur. We have defined the T cell reactivities to measles and mumps virus and to MAG in an immunospot assay which is based on the detection of secretion of interferon-gamma (IFN-gamma) by single cells upon stimulation with specific antigen in short term cultures. Patients with MS had higher numbers of MAG-reactive T cells in blood compared to controls, while no differences were observed for measles or mumps virus-reactive T cells. In CSF, elevated numbers of MAG-reactive T cells and also of measles- and mumps-reactive T cells were found in patients with MS compared to other neurological diseases. A strong accumulation of antigen-reactive T cells was observed in the MS patients' CSF compared to blood. The magnitude of these T cell reactivities did not correlate with clinical MS variables. The T cell repertoire in MS thus includes, besides myelin basic protein, proteolipid protein and myelin oligodendrocyte glycoprotein, also MAG and, in addition, measles and mumps virus. It is not clear whether these T cell reactivities accumulated in the CSF have importance for the pathogenesis of MS or reflect phenomena secondary to myelin damage, or result from both these alternatives.

Adolescent↗

PubMed1992

Effects of zimeldine and its metabolites, clomipramine, imipramine and maprotiline in experimental allergic neuritis in Lewis rats.

The influence of the selective serotonin (5-HT) reuptake inhibiting antidepressant zimeldine and its metabolite norzimeldine was tested on experimental allergic neuritis (EAN) in Lewis rats, which is an animal model of the Guillain-Barré syndrome (GBS) in man. Zimeldine and norzimeldine both suppressed clinical signs of actively induced EAN when given at a dose of 20 mg/kg/day intraperitoneally via osmotic pumps. The effects of zimeldine, its metabolites norzimeldine and CPP 200 as well as of the antidepressants clomipramine, imipramine and maprotiline on in vitro immune response were tested. Thereby we used an immunospot assay for interferon-gamma (IFN-gamma) produced by lymph node mononuclear cells (MNC), which reflects number of memory T lymphocytes activated by antigen or lectin, in this experiment bovine peripheral nerve myelin (BPM) and phytohemagglutinin (PHA), respectively. In the IFN-gamma secretion assay zimeldine, CPP 200, clomipramine and maprotiline all in a concentration-dependent mode reduced the number of IFN-gamma secreting cells while norzimeldine and imipramine did not affect the IFN-gamma secretion. In assays for proliferation in response to antigen or lectin, the concentration 10(-4) M was judged toxic for all substances tested, and at concentrations below that all but zimeldine showed a dose-dependent slight reduction of MNC proliferation. The action of several drugs on induced T cell secretion of IFN-gamma suggests that the mechanisms for the suppressive effect of zimeldine and norzimeldine on EAN symptoms can be due to an action on myelin T cell autoreactivity. All the monoamine reuptake inhibiting antidepressants tested in this study showed immunomodulatory effects by either a reduction of the number of IFN-gamma-secreting cells or the MNC proliferation. These observations call for further studies of immunological mechanisms in the pathogenesis of mental disorders as well as on the potential role of drugs acting on the monoamine systems in the treatment of recognized autoimmune diseases.

Animals↗

PubMed1992

The light chain of tetanus toxin inhibits calcium-dependent vasopressin release from permeabilized nerve endings.

The effects of tetanus toxin and its light and heavy chain subunits on vasopressin release were investigated in digitonin-permeabilized neurosecretory nerve terminals isolated from the neural lobe of the rat pituitary gland. Exocytosis was induced by challenging the permeabilized nerve endings with micromolar calcium concentrations. Tetanus toxin inhibited vasopressin release only in the presence of the reducing agent dithiothreitol. This effect was irreversible. The purified light chain of tetanus toxin strongly inhibited exocytosis in a dose-dependent manner with half-maximal effect at c. 10 nM. The action of the light chain was observed after only 2.5 min of preincubation. Separated heavy chain subunit had no effect on hormone secretion. Inhibition of vasopressin release could be prevented by preincubating the light chain of tetanus toxin with an immune serum against tetanus toxin. The data clearly demonstrate that in mammalian neurosecretory nerve endings tetanus toxin acts at a step downstream from the activation by Ca2+ of the exocytotic machinery and that the functional domain of this toxin is confined to its light chain.

Animals↗

PubMed1992

Calcium antagonists suppress experimental allergic neuritis (EAN).

We examined the influence of Ca++ antagonist drugs on immune response and the clinical course of experimental allergic neuritis (EAN). The Ca++ antagonists verapamil and flunarizine suppressed actively induced EAN in Lewis rats in a dose-dependent fashion when given continuously by osmotic pumps from the day of immunization. If given from onset of clinical signs, day 10 after immunization, verapamil alone had therapeutic effects. The beneficial effects of the drugs seem to be mediated primarily by an action on the autoimmune response, since in vitro lymphocyte proliferation in response to nervous tissue antigens was dose-dependently inhibited by both drugs, whereas the in vitro conductivity of demyelinated sciatic nerve was not significantly affected by the Ca++ antagonists. The suppressive effect on lymphocyte proliferation could partially be bypassed by protein kinase C activating phorbol ester alone or in combination with the Ca++ ionophore ionomycin, confirming a non-toxic effect of the Ca++ antagonists on lymphocytes.

Action Potentials↗

PubMed1992

Treatment of interstitial pneumonitis due to cytomegalovirus with ganciclovir and intravenous immune globulin: experience of European Bone Marrow Transplant Group.

Data on 49 allogeneic bone marrow transplant (BMT) recipients who developed interstitial pneumonia due to cytomegalovirus (CMV) were collected retrospectively. All patients were treated with ganciclovir and high doses of intravenous immune globulin, although types of immune globulins and schedules of treatment varied. Seventeen (35%) of 49 patients responded to treatment. Thirty days after the diagnosis of interstitial pneumonia, the survival rate among patients was 31%. CMV was detected in 81% of patients on whom autopsies were performed. The survival rate among patients who received total body irradiation (TBI) was significantly lower (11 [27%] of 41) than that among patients who did not receive TBI (six [75%] of eight; odds ratio = 12.3; P = .009). No other factor, including age, grade of graft-versus-host disease, types and dose of immune globulin used, or dose of ganciclovir, was correlated to survival. These results show that although survival of allogeneic BMT recipients with CMV interstitial pneumonia has improved, more than one-half of the patients still died of pneumonia. Thus, both prophylaxis for and treatment of CMV infection must be improved.

Adolescent↗

PubMed1992

Myelin antigen reactive T cells in cerebrovascular diseases.

T cell reactivities to the putative autoantigens myelin basic protein (MBP), MBP peptides with amino acid residues 110-128 and 148-165, and myelin proteolipid protein (PLP) were examined in patients with acute ischaemic cerebrovascular disease (CVD) and, for comparison, in patients with inflammatory neurological diseases and other neurological diseases. A quantitative measure of these T cell reactivities was obtained by assessing numbers of T cells among blood and cerebrospinal fluid (CSF) mononuclear cells that secreted IFN-gamma in response to antigen in vitro. Higher numbers of T cells reactive with each of these four antigens were detected in peripheral blood from patients with CVD compared with patients of the two control groups. Among blood cells from the CVD patients, their average number was 2.3-4.2/10(5) mononuclear cells. MBP reactive T cells were several-fold enriched in the CSF of CVD patients. The findings strongly suggest that brain damage in context with acute CVD leads to an in vivo expansion of myelin reactive T cells.

Adolescent↗

PubMed1992

The T-cell repertoire in myasthenia gravis involves multiple cholinergic receptor epitopes.

Antibodies against the alpha-subunit of the acetylcholine receptor (AChR) are found in most patients with myasthenia gravis and are considered to contribute to the receptor damage which leads to the characteristic signs and symptoms of the disease. This B-cell response is T-cell driven. Elevated T-cell reactivities to AChR and its alpha-subunit have been described in myasthenia gravis, and AChR alpha-subunit peptide reactive T-cell lines and clones preferentially recognizing certain defined sequence segments have been reported, thereby disclosing the possibility of specific immunotherapy. We have defined the T-cell repertoire to AChR, its alpha-subunit and the synthetic peptide sequences 100-117, 113-130, 143-163, 161-179, 207-225, 221-240, and 235-255 of the alpha-subunit in an immunospot assay which is based on secretion of interferon-gamma (IFN-gamma) by individual memory T cells upon stimulation with specific antigen in short-term cultures. Most patients with myasthenia gravis displayed T-cell reactivities to 1 to 6 different peptides. The mean numbers of T cells recognizing individual peptides varied in the myasthenia gravis patients between 1 per 77,000 and 1 per 167,000 peripheral blood mononuclear cells. None of the seven peptides evaluated could be identified as an immunodominant T-cell epitope, and any of them was found to dominate in individual patients. The numbers of T cells reacting with AChR and recombinant human AChR alpha-subunit were slightly higher (mean numbers 1 per 26,000 and 1 per 50,000 mononuclear cells, respectively). Such cells, as well as AChR alpha-subunit peptide reactive T cells, were also found in patients with other neurological diseases and in healthy subjects, but at lower frequencies and numbers. In myasthenia gravis, the elevated numbers of memory T cells recognizing multiple AChR alpha-subunit peptides may be crucial for the development of the disease, and the IFN-gamma released by such T cells might be important for its perpetuation.

Adolescent↗

PubMed1992

An immunogenetic heterogeneity in multiple sclerosis.

Two clinical forms of multiple sclerosis (MS), primarily chronic progressive MS (PCP MS) and relapsing/remitting MS (R/R MS) have been shown to differ in several respects. The results of genomic HLA class II typing with restriction fragment length polymorphism analysis of 62 MS patients from Western Norway, 42 with R/R MS and 20 PCP MS, are reported on here. As in previous studies of Swedish patients, the haplotype DRw17(3), DQw2 was found to be five times more common in R/R MS than in PCP MS. This finding supports the hypothesis that R/R and PCP MS are immunogenetically separate entities. In contrast with a previous investigation of Norwegian MS patients, no association of MS with glutamine at position 34 of the HLA-DQ alpha chain or with defined sequences of the HLA-DQB1 gene was found.

Adult↗

PubMed1992

Influence of the freezing-thawing-washing procedure on the cytomegalovirus DNA content of cellular blood products.

There is a proven relation between cytomegalovirus (CMV) infection in seronegative immunocompromised patients and transfusion of random CMV unscreened cellular blood products (BP), where the leukocytes are thought to be the vector of transmission. We examined whether freezing, thawing, and washing, in attempt to reduce the quantity of leukocytes, also reduces the CMV-DNA-carrying cells of BP of CMV-seropositive donors and their infectivity for fibroblasts, using the polymerase chain reaction (PCR). The leukocyte contamination of the thawed-washed erythrocyte concentrates was < 1 x 10(8)/l and of the thawed-washed platelet concentrates, approximately 2.5 x 10(8)/l. All plasma samples and most samples of BPs of the CMV-seronegative controls were PCR-CMV-DNA-negative. The differences of the PCR results with the samples of CMV-seropositive donors before and after freezing were not significant. Thus we concluded that freezing-thawing-washing of cellular BP could not eliminate all CMV-DNA-bearing leukocytes. Plasma carries low risk for CMV infection, if at all.

Blood Component Removal↗

PubMed1992

Oxytocin at physiological concentrations evokes adrenocorticotropin (ACTH) release from corticotrophs by increasing intracellular free calcium mobilized mainly from intracellular stores. Oxytocin displays synergistic or additive effects on ACTH-releasing factor or arginine vasopressin-induced ACTH secretion, respectively.

The potency of oxytocin (OT) in evoking ACTH secretion by isolated, superfused rat adenohypophyseal corticotrophs and its enhancement by CRF and arginine vasopressin (AVP) were analyzed. Each secretagogue effectively released ACTH from adenohypophyseal cells when added separately in pulsatile fashion in physiological concentrations based on hypophyseal portal blood (OT, 10 nM; AVP, 0.5 nM; CRF, 0.1 nM). OT released ACTH at concentrations as low as 1 nM. Moreover, a dose-response relationship up to 10 microM was revealed. Combinations of a constant amount of CRF (0.1 nM) with increasing concentrations of OT exerted a synergistic effect on ACTH release. In contrast, OT given in various concentrations in combination with AVP (0.5 nM) produced an additive effect on ACTH release. To study the mechanism of action of OT on ACTH secretion, cytosolic free calcium levels in single pituitary cells exposed to OT or AVP were measured using the calcium-sensitive fluorescent indicator Fura-2. Corticotrophs among mixed adenohypophyseal cell types in the primary cultures were identified by immunocytochemistry. More than 500 cells were individually stimulated with OT or AVP. Basal cytosolic free calcium levels ranged between 80-130 nM free calcium. The addition of 100 nM OT or 1 microM AVP increased the cytosolic free calcium concentration within 3 sec to values ranging from 500-800 nM. An increase in intracellular calcium ranging from 200-500 nM due to OT could still be observed after extracellular calcium depletion. Taken together, our data demonstrate that physiological concentrations of OT stimulate ACTH secretion, independent of the other ACTH secretagogues, by mobilizing calcium mainly from intracellular stores.

Adrenocorticotropic Hormone↗

PubMed1992

Conjugal multiple sclerosis: immunogenetic characterization and analysis of T- and B-cell reactivity to myelin proteins.

We describe two families with conjugal multiple sclerosis. Onset of symptoms in the husbands occurred 11 and 17 years after onset of relapsing/remitting symptoms in their wives. There were no similarities regarding clinical manifestations of MS within each family. Evaluation of T-cell repertoire by enumeration of cells secreting interferon-gamma in response to proteolipid protein (PLP), myelin basic protein (MBP), and to various synthetic MBP peptides revealed similar patterns of T-cell reactivity within the families both in MS-affected parents and unaffected children. Genomic HLA-DR-DQ typing showed that T-cell reactivity was independent of HLA class II phenotype. Analysis of B-cell responses in blood showed low numbers of cells secreting IgG, IgA, or IgM antibodies against MBP, PLP, myelin-associated glycoprotein, and myelin-oligodendrocyte glycoprotein both in MS-affected and unaffected family members. In conclusion, our study of two families with conjugal MS has shown a dominant T-cell response against the same MBP peptide within the family both in MS-affected parents and unaffected children, and this T-cell response seems to be independent of the HLA class II phenotypes of the family members.

Adult↗

PubMed1992

Preparation, purification and characterization of chlorohaemin.

Preparation of chlorohaemin (CAS 16009-13-5) is performed on the basis of the method of Labbe and Nishida (acetone-acetic acid-SrCl2 method) with some significant modifications. Instead of blood as starting material, a fresh preparation of purified human erythrocytes is used. This avoids any contamination with serum and erythrocyte proteins and lipids of the end product. Special care is taken to remove contaminating globin by introducing some specific purification steps during isolation and recrystallisation. The yield is in the range 65-75% of theory, and the purity of the product is better than 99.9% as shown by elemental analysis and specific tests on various compounds as possible contaminants which originate from the starting material such as lipids and proteins and/or from the different steps of preparation and purification during the procedure. The pure chlorohaemin which is the compound of choice as reference substance for the AHD method in haemoglobinometry is characterized by LSI mass spectrometry (m/z = 616, haemin ion), field desorption-mass spectrometry (m/z = 652), by IR-spectroscopy, and by UV/VIS absorption spectroscopy (pyridine haemochrome spectrum, AHD spectrum).

Blood Proteins↗

PubMed1992

Effect of stilbene-type anion channel blockers on the immune response during experimental allergic neuritis (EAN).

We have studied the role of anion channel gating for the autoimmune response in experimental allergic neuritis (EAN) induced by bovine peripheral myelin (BPM). The influence of the stilbene-type anion channel blockers SITS and DIDS on T cell function was assessed by measurement of proliferation and by counting of interferon-gamma (IFN-gamma) secreting cells (IFN-gamma-sc) in response to BPM and phytohemagglutinin (PHA). SITS caused a dose-dependent increase of spontaneous proliferative activity as well as of proliferation in response to the antigenic stimulus BPM. In contrast, the drug caused a decrease of proliferation of cells stimulated with PHA. The number of cells induced to IFN-gamma secretion was reduced by SITS. The suppressive effect was dependent on the degree of activity of cells without drugs. Cultures showing high numbers of BPM reactive T cells were more easily suppressed than cultures with low numbers of BPM reactive T cells. Our results suggest that anion channel gating is involved in the triggering of T cells to IFN-gamma secretion. The anion channel signal pathway in lymphocytes could be a target for pharmacological intervention in inflammatory disorders. In the presently used autoimmune model, EAN, the net effect of in vivo treatment with SITS resulted in worsening of clinical signs and increased inflammatory cell infiltration in sciatic nerve, whereas the in vitro conductivity of sciatic nerve was not significantly affected by the drug. Thus anion channel gating seems to regulate activities of immune cells, and drugs with anion channel blocking properties may have effects that enhance autoimmune disease.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1992

[Determinants of serum pentamidine concentration in the human].

By means of serial measurements of pentamidine in plasma, urine and feces the significance of biologically available dose, volume of distribution, elimination and dose interval for serum concentration is investigated in patients with AIDS and bone marrow transplantation after inhaled and intravenous application. Aerosolisation of the drug yields to serum concentration mostly below the detection limit (HPLC). In urine only 0.15 to 0.8% of the substance biologically available in the lung are measured as unaltered pentamidine-base. After i.v. infusion the dose dependent low serum concentrations of 30 to 100 ng/ml indicate a fast distribution in peripheral compartments from which a very slow deliberation is seen. The half-life of the drug is also dose dependent and amounts under clinical conditions at minimum four days. The fecal excretion is found to be only one third of that measured in urine. A difference in the kinetic of elimination between bone marrow transplantated and AIDS-patients could not be evaluated. For clinical therapy the most important pharmacokinetic variable seems to be the terminal elimination constant which would implicate a prolongation of the common dose interval.

AIDS-Related Opportunistic Infections↗

PubMed1992

[Risk factors and prevention of pneumocystis carinii pneumonia after bone marrow transplantation].

For six months after bone marrow transplantation (BMT) there is a risk of 5 to 15% to suffer from interstitial pneumonia due to pneumocystis carinii (PcP). Prophylaxis with trimethoprim/sulfamethoxazol is therefore routinely and successfully applied. However myelotoxicity, allergic reactions, augmentation of the risk of nephrotoxicity with cyclosporine A and noncompliance may be serious problems. Since the prophylaxis of PcP with pentamidine-aerosol proved to be effective in patients with AIDS, we conducted a prospective trial with regular inhalations of pentamidine. The aim of this study was to evaluate the toxicity, safety, practicability and possible resorption of pentamidine when applied as aerosol. The first of 43 patients were treated with 60 mg pentamidine on two days before, at the day of BMT and 14 days after BMT. Starting four weeks after BMT, 300 mg pentamidine were given every four weeks up to six months. After the study, the four 60 mg inhalations were replaced by two 300 mg inhalations before BMT, because this proved to be more convenient for the patients. There was no pneumonia due to pneumocystis carinii. The only noteworthy side effects observed were cough (19.8%), salivation (9.6%) and sore throat (5.7%). In general pentamidine was well tolerated and well accepted by the patients. Pentamidine could only be detected in the serum of 40 to 60% of all patients. In those patients the serum levels were 7.5 to 9 ng/ml and similar to concentrations found in comparable patients with AIDS. We conclude, that pentamidine-aerosol has only minor side effects, is well tolerated and safe and is therefore an attractive alternative for PcP-prophylaxis after BMT.

Administration, Inhalation↗

PubMed1991

T and B cell responses to myelin-oligodendrocyte glycoprotein in multiple sclerosis.

The pathogenesis of multiple sclerosis (MS) is believed to involve an autoimmune component directed against the myelin sheath. One potential target Ag for such autoimmune attack is the myelin-oligodendrocyte glycoprotein (MOG) because an anti-MOG mAb has profound influence on the course of experimental autoimmune encephalomyelitis, which to some extent represents an experimental model of MS. Using single cell assays, we have evaluated T and B cell reactivities to MOG in MS patients and controls. T cell reactivity was estimated by counting the number of cells that secreted IFN-gamma in response to MOG, whereas B cell reactivity was estimated by enumerating cells secreting antibodies that bound to MOG. MOG reactive T cells were detected in the peripheral blood of the majority of the 16 MS patients examined (mean 1/7299 mononuclear cells), but infrequently and at lower numbers in samples from neurologic controls. MOG-reactive T cells were more frequent among MS patients' cerebrospinal fluid (CSF) mononuclear cells (mean 1/450 cells). The T cell response to MOG was evidently MHC class II restricted, because Fab fragments of a rabbit polyclonal anti HLA-DR antibodies abrogated the Ag-induced increase in number of cells that secreted IFN-gamma, as analyzed on CSF and PBMC from three patients with MS. Anti-MOG IgG antibody-secreting cells were detected in blood in 8 of 16 MS patients (mean 1/25,641 cells), but they were also strongly accumulated in CSF, being detected in 8 of 10 MS patients examined (mean 1/265 cells), while rarely found in controls. The findings imply that MOG may represent a pathogenetically important target Ag in MS.

Adult↗