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Biomedical subjects

S Meuer

Publications and source records attributed to S Meuer.

68 records · Page 4Linked to original sources
PubMed1986

Ciclosporin and prednisone v. prednisone in treatment of Graves' ophthalmopathy: a controlled, randomized and prospective study.

Forty patients with Graves' ophthalmopathy stages III-V were divided into two groups in a random manner according to their year of birth. Group I received prednisone in decreasing dosage. Group II received prednisone at a comparable dosage and ciclosporin. Steroids were discontinued after 10 weeks in the two groups. In the patients of group II, ciclosporin was continued over 12 months. The therapeutic effect was assessed by an activity score based on subjective and objective symptoms (computerized tomography and sonography of the orbit, Hertel values, clinical findings). All signs of endocrine ophthalmopathy improved significantly in both groups (P less than 0.01 in group I; P less than 0.001 in group II). The improvement was significantly greater in group II (P less than 0.05) according to the predefined score. After corticosteroids were discontinued, inflammatory signs recurred in nine patients in group I and in one of group II. During the observation period of 12 months, relapses occurred in eight out of twenty patients in group I and in only one out of twenty in group II. Muscle thickness decreased in nine patients in group II, 6 months after beginning therapy. At this time, the results were not influenced in any of the twenty patients in group I. Microsomal antibodies decreased significantly (P less than 0.001) in the ciclosporin group, whereas no change was seen in the other group. Renal values rose within the normal range in group II. In this group, an infection with Klebsiella pneumoniae occurred in one patient after 4 months of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Chronic T cell leukemia with unusual cellular characteristics in ataxia telangiectasia.

A 27-year-old male patient with ataxia telangiectasia (AT) developed atypical chronic lymphocytic leukemia with increasing bone marrow infiltration in the absence of organomegaly. One-third of the leukemia cells expressed a mature suppressor/cytotoxic T cell phenotype (T3+ T4- T6- T8+ T10-), two-thirds demonstrated additional helper/inducer T cell-associated antigens (T3+ T4+ T6- T8+ T10-), and a small fraction reacted with a natural killer (NK) cell-specific monoclonal antibody (Leu 11+). The proliferative response to stimulation in vitro with lectins and various monoclonal antibodies resembled the proliferation pattern of mature thymocytes: The cells responded to phytohemagglutinin (PHA), concanavalin A (ConA), stimulation of the T3-Ti receptor complex with Sepharose-bound anti-T3, and stimulation of the sheep erythrocyte receptor protein with anti-T11(2) and anti-T11(3) in conjunction with exogenous interleukin-2 (IL 2); they failed, however, to proliferate after stimulation with anti-T11(2) and anti-T11(3) alone. There was no response in the mixed lymphocyte reaction (MLR) and no suppression of the MLR between two healthy donors. Antibody-dependent cell-mediated cytotoxicity and NK activity could not be demonstrated. Cytogenetic analysis revealed complex clonal aberrations, including an interstitial deletion of the long arm of chromosome 14 concerning bands q21-31, loss of chromosome 20, and loss of the Y chromosome. Cytostatic chemotherapy was of little use and caused serious side effects, whereas leukapheresis proved effective in reducing the tumor load. The clinical data and laboratory findings in this case correspond to three previously described patients with AT who developed chronic T cell leukemia. Thus, in adult patients with AT, malignant proliferation of cytogenetically marked and phenotypically heterogeneous mature T cells seems to be a frequent complication.

Adult↗
PubMed1984

Natural killer-like function of activated T lymphocytes: differential blocking effects of monoclonal antibodies specific for a 90-kDa clonotypic structure.

A monoclonal antibody termed anti-NKTb has been generated following immunization of mice with cloned human cells (JT9) displaying natural killer (NK)-like activity. This antibody has the capacity to block cytotoxicity of the immunizing clone against several targets. In the present study, anti-NKTb was compared with a monoclonal antibody termed anti-NKTa that had previously been generated against JT9 cells and that had also been shown to block the NK-like function of these cells. The expression of a NKTb determinant, like that of NKTa, was found to be restricted to two NK active clones derived from the same individual, JT9 and JT10, both of which have the same mature T-cell phenotype (T3+, T8+, T11+). Comodulation, immunoprecipitation, and competitive binding experiments showed that both antibodies are directed to the same 90-kDa heterodimer associated with the T3 structure on the cell surface. However, cytotoxicity blocking studies suggested that NKTa and NKTb may represent functionally distinct epitopes of this 90-kDa molecule. Anti-NKTa uniformly blocked the cytotoxicity of both JT9 and JT10 cells when tested against 11 randomly selected target cell lines. In contrast, anti-NKTb totally blocked the cytotoxicity of these cloned cells against some targets (i.e., HPB-ALL, Nalm-1) but had very little effect when cytotoxicity was measured against other target cells (i.e., K562, U937, KG-1). This selective blocking effect, therefore, supports the notion that the heterodimer defined by the NKT antibodies is involved in the process of target cell recognition rather than in the cytolytic pathway of the cloned effector cells. Moreover, the unique functional effects of anti-NKTb suggest that additional levels of complexity exist in the specific recognition mechanisms of these clonal populations of NK active mature T lymphocytes.

Antibodies, Monoclonal↗
PubMed1983

Identification of a clonally restricted 90 kD heterodimer on two human cloned natural killer cell lines. Its role in cytotoxic effector function.

The present studies were carried out to identify surface molecules involved in the cytotoxic effector function of a human natural killer (NK) clone termed JT9. This clone represents a mature T lymphocyte (T3+T8+T11+) mediating NK-like activity. Using JT9 for immunization, one monoclonal antibody termed anti-NKTa was selected that blocked the cytotoxicity of the clone towards K562 cells. Reactivity of anti-NKTa antibody was assessed using a large panel of lymphoid and nonlymphoid cells including a variety of cloned cell lines with either cytotoxic T lymphocyte (CTL) or NK-like activity. Among all cells tested, only two individual clones, JT9 and JT10, were found to express NKTa antigen. JT10 was derived independently from the same individual as JT9 and also represents a mature T cell (T3+T8+T11+) mediating NK-like activity. Like the Ti structure on CTL clones, the molecule defined by anti-NKTa was shown to be membrane associated with T3 in co-modulation experiments. Moreover, anti-NKTa precipitated a 90 kD heterodimeric structure in sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of 125I surface-labeled JT9 cells. The blocking capacity of anti-NKTa was evaluated in cytotoxicity assays using a panel of target cells. The influence of anti-T3 was tested in parallel and it was found that both anti-NKTa and anti-T3 blocked the cytotoxicity of the cloned cells against all targets. Given the potential role of 90 kD molecules as antigen-receptor structures, the specificity of the two NKTa+ NK clones was compared and found superimposable when assessed using 15 in vitro established cell lines. However, in contrast to conventional CTL clones, the expression of cytotoxicity by JT9 and JT10 was not dependent upon recognition of class I or class II major histocompatibility complex gene products on the target cells. In addition, the cytotoxicity of these T8+ NK active clones could not be blocked by anti-T8 antibodies. Taken together, the present data suggest that the specificity of one population of human NK active lymphocytes is determined by clonotypic structures. The NKTa determinant identified here appears to belong to the same family of molecules as Ti structures, previously identified on antigen-specific T lymphocytes.

Antibodies, Monoclonal↗
PubMed1983

Phenotypic and functional heterogeneity of human cloned natural killer cell lines.

Extensive efforts have recently been made to characterize cells capable of mediating natural killing activity (see ref. 1 for review) and increasing evidence has arisen that these cells were heterogeneous. By using the methods we have recently developed for cloning natural killer (NK) cells derived from peripheral blood, we have analysed the heterogeneity of human NK cells. Seven cell lines showing NK activity were established and studied for 4 months. Their phenotype was determined with a series of monoclonal antibodies; anti-T1, -T3, -T4, -T8, -T11, -T12, Mo1 and each cell line appeared to have a unique phenotype. Moreover, whereas some of these lines could only kill K562 cells, the standard assay of NK activity, others displayed a broad but distinct spectrum of reactivity against a variety of human tumour and viral transformed cell lines. Taken together, these results demonstrate the phenotypic and functional heterogeneity of NK effector cells which has recently been suggested in both human and murine systems.

Cell Line↗
PubMed1982

Low zone desensitization: a stimulus-specific control mechanism of cell response. Investigations on anaphylatoxin-induced platelet secretion.

The biologic activity of the anaphylatoxic peptides C5a and C3a is regulated efficiently at the target-cell level by the phenomenon of desensitization. Desensitization of platelets is stimulus specific and can be induced by low concentrations of anaphylatoxins without any preceding secretory event. In contrast to activation to secretion, desensitization is Ca++ independent but much more time consuming, especially at lower temperatures where both processes differ markedly in reaction velocity. This low zone desensitization insures that secretion from platelets only occurs when high amounts of anaphylatoxins are rapidly generated in the vicinity of the target-cell. Consequently, stimulus-specific unresponsiveness of the target cells can be induced by slowly increasing the concentration of the respective stimuli in their vicinity. Cellular control seems to act as a first-line mechanism of regulation, whereas the role of fluid-phase control is considered as preventing longer persistence and systemic accumulation of active anaphylatoxins.

Anaphylatoxins↗
PubMed1982

Antigen recognition by human T lymphocytes is linked to surface expression of the T3 molecular complex.

Four distinct surface molecules on human T cells are defined by the monoclonal antibodies anti-T1, anti-T3 (anti-T3A), anti-T11 and anti-T12. Following cell binding, anti-T3 (anti-T3A) and anti-T1 induce independent modulation of their respective ligands, whereas anti-T11 and anti-T12 do not. To explore the biological consequences of this modulation, we used cloned populations of T4 and T8 cytotoxic T lymphocytes. Anti-T3 (anti-T3A), but not anti-T1, inhibits cytotoxic T lymphocyte effector function by T4 and T8 clones as well as antigen-specific T cell recognition. The latter is not secondary to a generalized inhibitory effect since responsiveness to interleukin 2 is maintained. Moreover, after modulation, cytotoxic T lymphocytes recover cytolytic function in parallel with reexpression of surface T3 molecules. We provide evidence for a direct linkage between antigen recognition by T lymphocytes and surface expression of the T3 molecular complex.

Antibodies, Monoclonal↗
PubMed1982

Generation of a cloned NK cell line derived from the "null cell" fraction of human peripheral blood.

The present studies were designed to determine the conditions for generation of human NK clones. First the "null cell" (NC) fraction of human peripheral blood mononuclear cells, which contains the NK effectors, was purified using negative selection with anti-T3, anti-T8, anti-B1, and anti-Mo2 monoclonal antibodies. Subsequently, NC were cloned by limiting dilution using a combination of phytohemagglutinin (PHA) and lymphocyte-conditioned medium (LCM) as an initial stimulus. Colonies could be easily obtained with this procedure, but the maintenance of long-term growth of the cultures represented a major problem. A cloned cell line termed JT1 was generated and has been proliferating continuously in culture for more than 6 mo. The phenotype of JT1 cells was analyzed several times with a series of monoclonal antibodies. These cells did not express surface markers related to thymic (T3-, T4-, T8-, T11-), B cells (B1-, J5-), or myelomonocytic (Mo1-, Mo2-, MY7-) differentiation. In contrast, 95% of JT1 cells reacted with the anti-T10 monoclonal antibody. T9, Ia, and J2 antigens were also present on JT1 cells, but their expression appeared variable from one determination to another. This cloned cell line maintains a strong cytotoxicity against common NK targets, such as K562 and Molt 4 cell lines, and a moderate ADCC activity. In addition, after several months in culture, JT1 cells are still capable of being regulated by interferon, because this lymphokine rapidly enhances cytotoxicity against K562 cells.

Antibodies, Monoclonal↗
PubMed1981

Comparative study on biological activities of various anaphylatoxins (C4a, C3a, C5a). Investigations on their ability to induce platelet secretion.

Several anaphylatoxic substances (human C3a, guinea pig C3a, human C4a, guinea pig C5a, and a synthetic C3a-related hexapeptide) were compared with regard to their ability to induce secretion of [3H] serotonin from guinea pig platelets. Functional identity of the C3a preparations, C4a, and the hexapeptide was demonstrated by the phenomenon of crossed desensitization. Whereas C3a of human and guinea pig origin proved to be qualitatively and quantitatively identical, C4a expressed only 3% of the activity of the C3 fragments on a molar basis. Investigations with goat anti-guinea pig C3a demonstrate that human and guinea pig C3a possess one antigenic determinant in common; however, this determinant is not the C-terminal amino acid sequence. Addition of the anaphylatoxins with low doses of thrombin led to a potentiation of [3H] serotonin release from the platelets. Under these conditions C3a concentrations of 1.5 X 10(-10) mumol/liter (65 pg of C3a) could be detected. Thus the platelet system represents the most sensitive in vitro assay known for evaluation of biological activity of the C3a anaphylatoxins.

Anaphylatoxins↗
PubMed1981

Synthetic C3a analogs as specific inhibitors of C3a activity.

Various C3a-related C-terminal synthetic oligopeptides were investigated for their ability to induce a release of serotonin from guinea pig platelets. The results confirm earlier findings that expression of biological C3a activity requires the four to five C-terminal amino acids of the C3a primary structure and underlines the essential role of the C-terminal arginine. Besides their ability to induce a specific release reaction, these peptides--after short incubation with the platelets--lead to a specific desensitization of the cells for C3a or C3a-related stimuli. Expression of this inhibitory activity required concentrations of the peptides more than 100-fold lower than those that were necessary to induce secretion. The possibility of using C3a analogs as specific inhibitors for C3a offers a valuable tool for in vivo studies of biological C3a activity.

Amino Acid Sequence↗
PubMed1981

Platelet-serotonin release by C3a and C5a: two independent pathways of activation.

C3a and C5a were investigated for their ability to induce secretion of serotonin from platelets in a homologous guinea pig system. Platelets respond to either anaphylatoxin with a dose-dependent release that does not exceed a plateau at the 70% level. On a molar basis. C5a is about 50-fold more active than the C3 fragment. The C5a effects in the platelet system can be clearly distinguished from the activity of C3a and vice versa by a phenomenon of specific desensitization of the platelets to either stimulus. Our observations lead to the postulation of distinct receptors for C3a and C5a on guinea pig platelets as well as 2 independent pathways of platelet activation, which both lead to a specific release.

Animals↗
PubMed1978

Platelet activation: a new biological activity of guinea-pig C3a anaphylatoxin.

3H-serotonin-release from labelled gp-platelets is established as a sensitive method for testing a new biological activity of gp-C3a anaphylatoxin in an autologous situation. Time-, dose- and temperature-dependent release reactions as well as specific inhibition by carboxypeptidase B and anti-C3a antibodies show that C3a is a potent and specific inducer of platelet activation. Inactive C3a does not induce 3H-serotonin-release but specifically inhibits the action of C3a on platelets.

Anaphylatoxins↗
PubMed1978

The anaphylatoxic peptide C3a of guinea pig complement. I. Purification, physicochemical and antigenetic properties.

Highly purified guinea pig C3a was obtained after specific cleavage of isolated C3 by the alternative pathway enzyme VF-B in a one step procedure. It turned out to be a low molecular weight peptide with basic character (M.W. 9500; isoelectric point above 9.4). C3a represents an antigenetic determinant of its own in the native C3 molecule, different from the B determinant. Guinea pig C3a resistant to 100 degrees C for 10 minutes. Its smooth muscle contracting activity can be destroyed by trypsin and carboxypeptidase B. These findings indicate that guinea pig C3a is quite similar to human C3a.

Anaphylatoxins↗