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Biomedical subjects

A Erdei

Publications and source records attributed to A Erdei.

At least 73 records · Page 4Linked to original sources
PubMed1984

Role of C3b receptors in the enhancement of interleukin-2-dependent T-cell proliferation.

The mechanism by which the complement system influences immune responses to T-cell-dependent antigens has not yet been clarified. That is why we studied the effect of the third complement component (C3) on different T-cell-dependent processes using well-defined mouse T-cell lines. While C3 did not influence the interleukin-2 (IL-2) production of the ST2/K-9 helper T-cells, the IL-2-dependent proliferation of the ST1 line was shown to be dose-dependently enhanced by C3. It is proved that neither the haemolytic activity of C3 nor the C3a fragment had any role in the process. The effect of C3 on the IL-2-dependent T-cell growth is even more enhanced (up to five-fold) when using polymerised C3. When the ST1 cell line is cultured in the presence of the cross-linked ligand, T-cells formed 80% less rosettes with red blood cells coated with antibody and mouse or human C3b. It is strongly suggested that C3--particularly when aggregated--exerts its enhancing effect on the growth of IL-2-dependent cell lines by binding to C3b receptors present on such T-cells.

Animals↗
PubMed1984

C3 cleaved by membrane proteases binds to C3b acceptors expressed on concanavalin A-stimulated human lymphocytes and enhances antibody-dependent cellular cytotoxicity.

On activation of cells membrane-associated proteases--including serine esterases known to cleave the third component of complement (C3)--become expressed. In this paper it is shown that as a consequence of this enzyme activity isolated native human C3 added to concanavalin A (Con A)-activated human lymphocytes is cleaved on the surface of the blast cells. This enables the immediate fixation of nascent C3b (C3bx) through its short-lived metastable binding site to C3b acceptors (C3bA's) newly expressed on Con A-stimulated cells. Acceptor-bound C3b is detected by the immune adherence rosette formation of the C3-treated Con A blasts with the C3b receptor (C3bR)-bearing O, Rh+ erythrocytes (32 +/- 4%). The cleavage of C3 and the covalent fixation of C3b are shown to be inhibited by phenylmethylsulphonyl fluoride and methylamine, respectively. As a functional consequence of the covalent fixation of C3b to the mitogen-activated lymphocytes it is demonstrated that the antibody-dependent cellular cytotoxicity (ADCC) of these cells against O, Rh+ erythrocytes sensitized with anti-D IgG is significantly enhanced. The C3 specificity of the process and the role of C3bR's of the target cells are proved. It is postulated that effector cell-bound C3b amplifies ADCC by improving effector cell-target cell contact.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1983

IgG-Fc receptors differ in sensitivity to primary amines.

The effect of 12 different amines was tested on the IgG-Fc receptor (IgG-FcR) function of human peripheral mononuclear blood cells (PMBCs). While histamine and to a lesser extent dopamine resulted in a higher ratio of EA-rosette forming cells, a group of amines, like methylamine, dansylcadaverine, hydroxylamine and some others inhibited the EA-rosette formation. Neither the enhancement nor the inhibition was found to be mediated through direct interaction of amines with the Fc portion of the IgG molecule or the IgG-FcR. Only a portion of IgG-FcRs are sensitive to the amine-mediated inhibition and the results suggest that amines inhibit the cluster formation of IgG-FcRs.

Amines↗
PubMed1983

C3b acceptors on macrophages: inhibition of Fc gamma-receptor-mediated phagocytosis by acceptor-bound C3b.

The binding of nascent human C3b (i.e. the fragment of C3 just after trypsin cleavage) to mouse peritoneal macrophages was demonstrated by immune adherence. Acceptor-bound C3b could be detected longer than 24 h on the cell membrane. The rosette formation and phagocytosis of SRBC coated with anti-SRBC rat IgG was inhibited by preincubation of the cells with C3 and trypsin (15 min, 37 degrees C). However, the phagocytosis of opsonized yeast particles was not influenced by acceptor-bound C3b, proving that C3b-C3b acceptor interaction did not alter the function of C3b-receptors. Acceptor-bound C3b on the macrophages failed to mediate phagocytosis of human 0,Rh+ red cells having C3b-receptors.

Animals↗
PubMed1983

Conditions for the enhancing effect of protease inhibitors on the concanavalin A induced thymidine response of murine lymphocytes.

Incorporation of [3H]-thymidine - [3H]-TdR - into concanavalin A (Con A) stimulated murine splenocytes and thymocytes was found to be enhanced by addition of certain concentrations of phenyl-methylsulfonylfluoride (PMSF), di-isopropylfluorophosphate (DFP), N-alpha-tosyl-L-lysyl-L-chloromethylketone (TLCK), and soybean trypsin inhibitor (SBTI). No enhancement could be observed when mononuclear cells of the peripheral blood were used, and a medium enhancement when thymocytes were applied. Furthermore, no enhancing effect of the protease inhibitors (PI) on the Con A response of murine splenocytes could be observed within the first 24 h of the culturing period. DFP, PMSF, and TLCK enhanced the Con A response to a similar degree, whereas SBTI was less effective. DFP and SBTI proved to be also effective when they were added after 15-24 h to the Con A cultures, if the cultures were harvested 48 h later. Removal of adherent and phagocytic spleen cells or reduction of the concentration of spleen cells shifted the effective DFP concentration to lower concentrations, whereas addition of adherent spleen cells caused a shift of the enhancing DFP amounts to higher concentrations. The data presented suggest that the enhancing effect of PI on the T cell response depends on the concentration of PI, the time of culturing and incubation, the PI used, the origin of the stimulated cells, and especially on the number of adherent and phagocytic cells. These findings might explain - at least in part - the different results on the effect of PI on the T cell response obtained in the past.

Animals↗
PubMed1983

C3b acceptors on human peripheral blood mononuclear cells; characterization and functional role.

C3b acceptors (C3bAs) of human peripheral blood mononuclear cells (PBMC) reacting with the labile binding site of nascent C3b(C3bx) have been investigated by the immune adherence (IA) test. In non-cellular systems some conventional chemical groups (OH-, NH-2) have been reported to be the target of the covalent binding of C3bx. Thus it should be assumed that every cell can fix C3bx via its labile binding site and C3bAs are barely saturable. Contrary to this expectation, however, normal human PBMC were found to be heterogeneous from this point of view, as 57 +/- 4% of B cells and 21 +/- 2% of Null cells possess C3bAs while T cells do not. C3bAs of human PBMC are saturable and trypsin-sensitive structures. The covalent nature of the C3bx-C3bA interaction has also been proved. Studying the effect of acceptor-bound C3b on the function of other cell-surface structures, the inhibition of the Fc gamma receptor function and the abolishment of the enhancement of pokeweed mitogen-stimulated blastogenesis by immune complexes were found.

Antigen-Antibody Complex↗
PubMed1982

The influence of tissue transglutaminase on the function of Fc receptors.

In contrast to FcRII the soluble Fc receptor (FcRI) of human peripheral mononuclear blood cells (PMBC) is shed from PMBC following a 4-37 degrees C temperature shift and inhibits rosette formation of nonshed PMBC with antibody-coated erythrocytes (EA). Purified FcR, could be polymerized by tissue transglutaminase as was revealed by SDS-polyacrylamide gel electrophoresis. Comparing the Sephadex G-150 elution profile of the EA rosette inhibitory capacity of FcRI vs FcRI incubated in the presence of transglutaminase, the latter was found in a higher mol. wt region and could inhibit rosette formation by both FcRI and FcRII. Furthermore, the shedding of FcRI could be prevented by the addition of transglutaminase or Ca2+-ionophore A23187 (which leads to the activation of PMBC transglutaminase) to the cell suspension. The function of FcRII was not affected by either the addition of transglutaminase or Ca2+-ionophore to the cells. The results point to the involvement of transglutaminase in the determination of the functional state of the Fc receptor on the cell surface.

Cell Membrane↗
PubMed1982

Differential effect of low molecular weight alcohols on the Con A stimulation of mouse spleen cells.

Incorporation of [3h]thymidine ([3H]TdR) into concanavalin A (Con A)-stimulated murine splenocytes was found to be enhanced by addition of certain concentrations of ethanol, 2-propanol and acetone. The alcohol/acetone-induced enhancement of the Con A response was found to be accompanied by an increase of the percentage of living cells as assessed by trypan blue exclusion. Concentrations of ethanol and 2-propanol which caused maximum [3H]TdR uptake in Con A cultures were also found to lead to higher percentages of aggregated cells than in comparison to Con A cultures without alcohol. The data suggest that alcohols in certain concentrations are capable to achieve optimum Con A stimulation.

Alcohols↗
PubMed1981

Interference of beta 2-microglobulin specific autoantibodies with EA-binding of human peripheral lymphocytes; inhibition of B-cell and enhancement of T-lymphocyte Fc-receptors.

The effect of anti-beta 2 m-specific autoantibodies was investigated on the FcRs of human PBMCs. Anti-beta 2 m autoantibodies inhibited the FcRs of the lymphocyte subpopulation detectable by rosetting with EA(hu). On the contrary, when EA(ox) indicator system was used, in the majority of the cases an enhancement of EA rosette formation was detected. Using separated lymphocyte subpopulations we found that the binding of anti-beta 2 m autoantibodies increased the number of FcR+ non-B-cells and inhibited that of B-lymphocytes.

Animals↗
PubMed1981

Human beta 2-microglobulin is a substrate of tissue transglutaminase: polymerization in solution and on the cell surface.

Incubation of purified human beta 2-microglobulin (B2-m) with tissue transglutaminase (Tgase) resulted in the formation of high molecular weight polymers revealed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In the presence of 30 mM [14C]methylamine, the polymer formation was prevented, but incorporation of methylamine into beta 2-m (equal to 1 methylamine per 1 molecule) could be observed. From the sheddings of peripheral blood mononuclear cells occurring in the presence of Tgase, it is apparent that anti-beta 2-m immunoadsorbent removed, in addition to human leukocyte antigen (HLA) and beta 2-m, some other proteins. The enzyme could incorporate [14C]methylamine into beta 2-m of the shedding cells. On addition of rabbit anti-human beta 2-m antibody, followed by fluoresceine-labeled goat anti-rabbit IgG antibody to human mononuclear blood cells, the otherwise homogeneous distribution of fluorescence turned into spots and patches on cells previously incubated with Tgase or Ca2+-ionophore A23187.

Beta-Globulins↗
PubMed1979

The heterogeneity of Fc receptors on human peripheral mononuclear blood cells.

Fc-receptor positive peripheral blood mononuclear cells (PMBC) behaved differently after a temperature shift from 4 to 37 degrees. Two types could be distinguished. Type I FcRI+PMBC were transformed to FcR-while type II FcRII+PMBC retained their FcR as measured by EA rosettes. The supernatants of the PMBC or the shed receptor purified on a Sepharose 4B-aggregated human IgG column blocked the EAR formation of FcRI+PMBC but had no effect on EAR information of FcRII+PMBC. An investigation was made into the reason why rosette formation by Fcrii+ cells could not be inhibited by FcRI. As an explanation, the role of differences in affinity or subclass specificity was excluded while the binding site(s) on the IgG molecule for FcRI and II proved to be different. The FcRII+PMBC had a greater cellular avidity for sensitized erythrocytes than FcRI+PMBC. The different states of FcR-s in the cell membrane are discussed as a possible source of heterogeneity.

Antibody Affinity↗