Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where G. A. Medgyesi is active.

Publication


Featured researches published by G. A. Medgyesi.


Molecular and Cellular Biochemistry | 1986

Bidirectional effect of met-enkephalin on macrophage effector functions

Gabriella Fóris; G. A. Medgyesi; Mátyás Hauck

SummaryMet-enkephalin (ME) exerts a bimodal effect on functional activities of rat peritoneal macrophages (PM); in a range of low concentration (10-9-10-7 M) antibody dependent cellular cytotoxicity (ADCC)was markedly stimulated with a simultaneous decrease of Fcγ receptor (FcγR) mediated phagocytosis while the opposite was observed at 10-6-10-5 M concentrations.Studying the possible underlying mechanism(s) the followings were recorded: (1) ME in all applied concentrations induced an early Na+ influx which was followed by a Ca2+ efflux in the range of low concentrations. In the range of high concentrations Na+ influx was accompanied by a Ca2+ influx. (2) ME at 10-8 M concentration induced a rise in cGMP level with a plateau in the 60–120th min of incubation. This effect was prevented by 10-5 M of naloxone. At 10-6 M concentration a transient rise of cAMP level was recorded which was not affected by naloxone. (3) Verapamil in 10-6 M abolished both the Ca2+ influx and the rise in cAMP level induced by 10-6-10-5 M ME but not the rise in cGMP level induced by lower ME concentrations. (4) cAMP elevation by high ME concentrations was abolished by enkephalinase inhibitory puromycin. (5) PM-enkephalinase as assessed by the cleavage of fluorogenic substrate L-alanine beta naphthylamide (ABNA), was inhibited by 10-6-10-5 M of ME. This inhibition was abolished by verapamil, but not affected by naloxone. In the range of low concentrations ME appears to act on specific delta opioid receptors and its action is positively coupled to guanylate cyclase. In relatively higher concentrations ME-action is not mediated by specific delta opioid receptors and it appears to involve Ca2+ influx, adenylate cyclase activation as well as the processing of hormone by PM-enkephalinase.


Molecular Immunology | 1984

Met-enkephalin induced alterations of macrophage functions

Gabriella Fóris; G. A. Medgyesi; Edit Gyimesi; Mátyás Hauck

Met-enkephalin /Met-enk/ was found to stimulate IgG2a-mediated antibody dependent cytotoxicity /ADCC/ of thioglycollate elicited rat peritoneal macrophages /PM/ through naloxone-sensitive opiate receptors in concentrations ranging from 10(-9) - 14(-7) M. Phagocytosis of IgG2a coated 51Cr-sheep red blood cell /SRBC/ was suppressed by M-enk in the same concentration range. In the same range of concentrations, M-enk was observed to induce a significant increase in the generation of luminol dependent chemiluminescence /LDCL/. The observed stimulation of ADCC was abolished by calmodulin inhibitor triflouroperazine /TFP/ in 10(-6) M concentration. The involvement of cyclic nucleotides in the M-enk induced functional alterations is indicated by finding cGMP accumulation to be augmented in M-enk treated PMs.


Clinical Immunology and Immunopathology | 1976

Functionally active C1 on the surface of human peripheral lymphocytes: Its role in the complement-mediated inhibition of the Fc receptor of B lymphocytes

George Füst; Anna Erdei; Gabriella Sármay; G. A. Medgyesi; J. Gergely

Abstract Guinea pig and fresh human serum inhibit the binding of aggregated human IgG to human peripheral B lymphocytes. It has been confirmed that this inhibition is mediated through the activated complement system. The presence of functionally active C1 was demonstrated on the surface of human peripheral lymphocytes. The role of surface C1 was studied in the activation of the complement system during the complement-mediated inhibition of the binding of IgG aggregates to Fc receptors of human B lymphocytes. Elimination of C1 from the surface of lymphocytes by EDTA treatment almost fully eliminated the inhibitory effect of serum on the aggregated IgG binding. The significance of the C1 on lymphocytes in the modulation of the immunoglobulin binding function of Fc receptors is discussed.


Immunochemistry | 1978

The effect of immune complex composition on complement activation and complement dependent complex release

Eva Rajnavo¨lgyi; G. Fu¨st; Judit Kulics; Julia Ember; G. A. Medgyesi; J. Gergely

Abstract The complement activating capacity and complement dependent complex release activity (CRA) of immune complexes (IC) formed at different antigen:antibody ratios were investigated. The correlation between antibody avidity, precipitating capacity and the effect of these parameters on Fcdependent biological functions was studied in BSA-anti-BSA and OA-anti-OA systems. The results suggest that antibody excess favours the complement activating effect of ICs. No correlations between antibody precipitating capacity and avidity was found. However, antibody avidity and complement activating capacity were related: the higher the avidity index of antibodies, the higher the complement activation. The kinetics of CRA are not directly influenced by these characteristics of antibodies. The intercalation of C3b into the lattice interferes not only with the primary antigen—antibody bonds, it may result in the rearrangement of the lattice through the disruption of the non-specific intermolecular interactions.


Clinical Immunology and Immunopathology | 1977

Studies on the mechanism of the complement-mediated inhibition of the Fc and C3 receptors of B lymphocytes

Anna Erdei; G. Füst; Gabriella Sármay; G. A. Medgyesi; J. Gergely

Abstract The mechansim of the complement-mediated inhibition of the Fc receptors on human peripheral lymphocytes incubated with normal serum was studied. The pretreatment of lymphocytes with a purified C1-esterase inhibitor preparation almost completely blocked the inhibitory effect of the serum on the binding of FITC-conjugated IgG molecules. Twenty to twenty-five percent of the cells in a lymphocyte suspension incubated in normal human serum became immune adherance positive. When normal lymphocytes were treated with a C3 preparation, no inhibition of the IgG aggregate binding occurred. However, if the C3b fragments were cleaved from the C3 molecules in the presence of lymphocytes a strong inhibitory effect on the Fc receptors was observed. The same inhibition by C3b was demonstrated after the digestion of the C3b receptors from the surface of lymphocytes. Furthermore, the EAC rosette formation was inhibited on lymphocytes incubated in normal serum. Pretreatment of the cells by C1-esterase inhibitor or elimination of C1 by EDTA also strongly reduced this effect of the serum. It was concluded from these findings that C1 present on the surface of lymphocytes triggers the classical pathway activation in the serum. During the complement activation, C4b and C3b fragments are cleaved from the C4b and C3 molecules. Part of these fragments fixes to the C3b receptors of the B lymphocytes and inhibits the ability of these cells to form EAC rosettes. The second part of the C4 and C3b fragments binds to the membrane of lymphocytes through their labile binding site outside the C3b receptors. The possible relationship of the portion of lymphocyte membrane which fixes the labile binding sites of the complement-derived fragments and the Fc receptors is discussed.


Cellular Immunology | 1983

Effect of low-molecular-weight lymphokine components on the Fc and C3b receptor-mediated macrophage functions

Gabriella Fóris; Mátyás Hauck; Balazs Dezso; G. A. Medgyesi; George Füst

Rat lymphokine (LK) components of 500--2500 MW separated on Sephadex G-15 column (FrA) were tested for their effect on Fc and C3b receptor activities of rat resident (rPM) and thioglycollate-provoked (pPM) peritoneal macrophages. Functions of the receptors were studied by measuring the adherence and uptake of 51Cr-labeled sheep red blood cells (SRBC) mediated by isolated rat anti-SRBC IgM or IgG2a antibodies and human C3, respectively. On rPMs mainly Fc mu receptors (Fc mu Rs) were affected by FrA; at low concentration (20 micrograms/ml) adherence was increased and phagocytosis was inhibited. At higher concentrations (40-80 micrograms/ml) a reverse effect was observed: adherence was inhibited and phagocytosis increased. On pPMs IgG2a-mediated functions were mainly affected by FrA with a concentration dependence like that observed with Fc mu Rs on rPM monolayers. A concentration-dependent enhancement of C3b receptor (C3bR)-mediated adherence by FrA was observed on both PM types. On pPms C3bR-mediated phagocytosis was enhanced as well.


Immunochemistry | 1975

Factors affecting chain-interactions in immunoglobulins and their significance in cold-agglutinin activity.

Éva Rajnavölgyi; A.C. Wang; G. A. Medgyesi; J. Gergely

Abstract In competitive recombination experiments using non-alkylated heterologous H and L chains of monotypic immunoglobulins of different classes, subclasses and VL subgroups, an order of sequence in preferential reassociation of chains was proved. Preferential association on class and subclass level was found when H and L chains obtained from proteins of different classes and subclasses were used. The influence of the VL subgroup property was only found, when the chains were derived from proteins of identical subclasses. There was no significant difference between the attachment to H chains of autologous and heterologous L chains of identical subgroups. The influence of the exchange of L chains with heterologous L chains of different subgroups on the antibody activity of IgMK cold-agglutinins was also controlled. Molecules containing μ chains of IgMK cold-agglutinins and heterologous L chains agglutinated erythrocytes at +4°C. The fixation of isolated μ chains of IgMK cold-agglutinin antibodies to erythrocytes at +4°C was also demonstrated. The importance of the folded structure in preferential association of immunoglobulin polypeptide chains and significance of the overall conformation of the immunoglobulin molecules in antibody activity is discussed.


Immunochemistry | 1976

Study of the interaction between monoclonal IgM proteins and the complement system

G. Füst; Mária Csécsi-Nagy; G. A. Medgyesi; Judit Kulics; J. Gergely

Abstract The capacity to activate the complement system and to fix isolated C1 of different monoclonal IgM proteins and various fragments was studied. All the 8 different IgM proteins tested fixed isolated C1, but the dose of the IgM preparations necessary for the fixation of the 50% of the available C1 activity strongly differed from each other. The complement activating (anti-complementary) effect of the IgM preparations was weak. (Fcμ)5 fragments prepared by tryptic digestion from 4 different IgM proteins and separated by gel filtration at pH 8.0 could fix C1 and their anti-complementary effect significantly increased with respect to the original IgM preparations. It was demonstrated that the C1-fixing ability of the (Fcμ)5 fragment was lost after gel filtration at pH 3.0 and a C1-fixing low mol. wt peptide fraction was released from the (Fcμ)5. This peptide recombined with the non-C1-fixing (Fcμ)5 and restored its ability for the C1-fixation. It was shown, furthermore, that the (Fcμ)5 preparation which could not fix isolated C1, activated the complement system via the alternative pathway.


Cellular Immunology | 1981

Receptors for IgM on rat spleen cells.

Ferenc Uher; M. Sándor; G. A. Medgyesi; J. Gergely

Abstract Ox red blood cells (ORBCs) sensitized with rat IgM antibodies formed antibody-coated red blood cell rosettes (EAR) around 9% of rat spleen cells freshly prepared at 4 °C, while an enhancement of the rosette-forming cell (RFC) frequency to 18–20% was observed after having exposed the spleen cells to a temperature shift from 4 to 37 °C. Although the temperature shift was found to increase the RFC frequency, a shedding of IgM-Fc receptors IgM-FcR into the medium was also detected (IgM-FcR-I). Regeneration of shed receptors within 5 hr has been proved, and the sheading-regeneration cycle could be repeated several times. IgM-Fc receptors detectable after the temperature shift (IgM-FcR-II) are neither shed nor detectable on freshly prepared spleen cells. This latter type of receptor is expressed only after incubating the cells at 37 °C for an optimal period of 8–10 hr. Both type I and II IgM-FcRs were detected on T lymphocytes as well as B lymphocytes; therefore they do not mark subpopulation. Both receptors are sensitive to trypsin and the activity of both requires Ca2+ ions. Shed receptors are able to inhibit EAR formation by cells carrying either IgM-FcR-I or IgM-FcR-II. They are sensitive to higher temperatures and agglutinate ORBCs sensitized by IgM antibodies in the presence of Ca2+ ions. EAR-inhibiting capacity was detected in two fractions obtained by gel chromatography of the supernatant after shedding. The elution volume of one of the active fractions corresponds to 130,000 daltons (D), and that of the other to approximately 50,000 D.


Immunology Letters | 1980

Complement-dependent inhibition of Fc receptors on human peripheral blood mononuclear cells: inhibition of the binding of aggregated IgG, soluble and particulate immune complexes

Anna Erdei; G. Füst; G. A. Medgyesi; J. Gergely

Abstract In our previous papers the complement-dependent inhibition of aggregated IgG binding to peripheral blood mononuclear cells (PBMC) preincubated with normal human sera or with C3b generated in the presence of lymphocytes was described. In this paper the complement-dependent inhibition of the binding of soluble [ 125 I]BSA-anti-BSA and particulate E hu A anti-D immune complexes (ICs) is described. Nascent C3b fragments, generated either in fresh serum during activation of the classical complement pathway or from native C3 molecules by trypsin, in the presence of the cells inhibited the binding of ICs to the cells. A comparison of the complement-dependent inhibition of different Fc-receptor (FcR) ligands revealed that the fixation of aggregated IgG was more intensively inhibited than that of particulate or soluble ICs. A possible mechanism of the binding of different FcR ligands — aggregated IgG and ICs — to the cell membrane and the causes of the differences in the inhibition induced by C3b fragments fixed to the acceptor sites on PBMCs is discussed.

Collaboration


Dive into the G. A. Medgyesi's collaboration.

Top Co-Authors

Avatar

J. Gergely

Eötvös Loránd University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Anna Erdei

Eötvös Loránd University

View shared research outputs
Top Co-Authors

Avatar

G. Füst

Eötvös Loránd University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Judit Kulics

Eötvös Loránd University

View shared research outputs
Top Co-Authors

Avatar

M. Sándor

Eötvös Loránd University

View shared research outputs
Top Co-Authors

Avatar

Éva Rajnavölgyi

Eötvös Loránd University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge