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Biomedical subjects

M Sandor

Publications and source records attributed to M Sandor.

72 records · Page 4Linked to original sources
PubMed1988

The binding of IgG1 containing immune complexes to the FcR of allogenically activated T cells induces changes in the membrane potential and the cell surface charge.

The effect on membrane potential and cell surface charge of binding immune complexes containing IgG1 and IgG2a monoclonal antibodies to Fc receptors was studied in resting and allogenically activated murine T cells. IgG1 complexed by antigen or heat aggregation induced electrophysiological changes on activated T cells. A biphasic alteration of membrane potential was detected by measurement of the intra- and extracellular distribution of the fluorescent dye, DiOC6. A short-lived hyperpolarization, detectable for 4-6 min after adding the respective ligand, was followed by a longer lasting depolarization. The cell surface charge, measured by cell electrophoresis, was also changed. This alteration was detected 2-4 hr after addition of immune complexes and disappeared by the 8th hr of incubation. Monoclonal antibody 2.4.G2, reactive with mouse FcR, induced a similar membrane potential response on activated T cells, but did not affect the cell surface charge. Monomeric IgGs and complexes of IgG2a did not modify these parameters. FcR ligands had no effect on the studied characteristics of resting T cells.

Animals↗
PubMed1988

Immunoglobulin (Fc) receptors on murine T- and B-lymphocytes: investigations using tumor models.

Lymphoid tumors are productive experimental models for the study of lymphocyte immunoglobulin receptors. Investigations with Fc receptor expressing lymphoid tumor cells have generated much useful information about: (a) the developmental expression of the different classes of Fc receptors on lymphoid cells of the T- and B-lineages; (b) the biochemical steps involved in the regulation of Fc receptor expression on lymphoid cells; (c) the structures of lymphoid cell Fc receptors and their genes; (d) the signals that induce alterations in the expression of Fc receptors on lymphoid cells; and (e) the molecular specificity of the binding of immunoglobulin to lymphoid cells Fc receptors. In addition, tumors that secrete immunoglobulins are providing useful models for analysis of the mechanisms by which B-cells influence Fc receptor expression and function on T-cells. An interesting, bi-directional immunoregulatory circuit involving Fc epsilon R+ host T-cells and IgE-secreting hybridoma cells has been identified that could prove useful in the analysis of the regulation of epsilon heavy chain expression. The studies discussed in this article and elsewhere in this volume serve to emphasize that, in addition to being clonal sources of key molecules such as Fc receptors and their messenger RNAs, lymphoid tumor cells that express Fc receptors are powerful and unique experimental models for investigating the developmental biology, regulation and function of lymphocyte Fc receptors.

Animals↗
PubMed1986

[Comparative studies of Fc receptors for IgG on resting and activated mouse T lymphocytes using different methods].

Fc-receptors for IgG (Fc gamma R) on resting (i.e. freshly prepared) and mitogen (Con A) or alloantigen-activated mouse spleen T cells were compared using binding of different markers such as 125J-labelled immune complexes, 125J-labelled anti Fc gamma R monoclonal antibody, FITC-labelled aggr. IgG and sheep erythrocytes covered with specific antibody (EA rosetting). C3b receptors were detected by rosetting with sheep erythrocytes covered with antibody and complement (EAC rosetting). The electrophoretic mobility of the cells without or after binding of aggr. IgG was also tested. A number of differences between resting and activated T cells were found: After activation of T cells by mitogen or alloantigen, a proportion of Fc gamma R-positive cells increased two to four times. Fc gamma R number per Fc gamma R-positive cell seemed to be higher on activated then on resting cells. Fc gamma R-positive resting cells did not shed their Fc gamma R upon incubation at 4 degrees C followed by incubation at 37 degrees C, but Fc gamma R-positive activated cells shed a remarkable proportion of their Fc gamma R on the same conditions. Binding of aggr. IgG caused a decrease of electrophoretic mobility of activated but not resting cells. Fc gamma R-positive resting cells were also C3b receptor-positive, whereas Fc gamma R-positive activated cells had no detectable C3b receptors.

Animals↗
PubMed1982

Enhancing effect of concanavalin A on the hemolytic activity of anti-Forssman IgG: the role of C1.

Native tetravalent Con A and the divalent acetylated derivative increased the hemolytic titer (i.e., the reciprocal of the antibody dilution required to give an average of one lytic site per sheep erythrocyte) of IgG antibodies against Forssman antigen by up to 225% with guinea pig and human complement. Although the average number of lytic sites generated at each antibody concentration increased, the slope of the titration curve did not change. Other lectins with the same or different sugar specificity either augmented or inhibited hemolysis but were less potent than Con A. Augmentation by Con A was consistent with the ability of lectin on the cell surface to bind but not activate guinea pig C1. Thus it appears that cell-bound Con A and IgG yield a complex that behaves like a doublet of IgG antibody molecules in its ability to fix and activate C1, when activation is dependent on the IgG component. In contrast, the highest dose of Con A inhibited by at least 50% the hemolytic activity of IgG antibodies against either a sugar-free protein (HSA) or a protein reactive with Con A (human myeloma IgE) using cells to which these antigens were coupled with chromic chloride. This suggests that the identity, density, and/or mode of presentation of the antigen on the cell surface may be important determinants of lectin-induced augmentation. Although both the enhancement or inhibition by Con A in the presence of whole C correlated with the number of C1 molecules bound and activated, there was no correlation with the ability of the lectin to agglutinate the cells.

Antigen-Antibody Complex↗
PubMedDate not supplied

The role of carbohydrates in the IgG binding and suppressive activities of shed human Fc receptors.

IgG Fc receptor (Fc gamma R) shed from human peripheral mononuclear cells and purified by IgG affinity chromatography bound to ConA, Pisum sativum, Ulex europeus and peanut lectins. The soluble Fc gamma R was not absorbed by wheat germ, soyabean, lentil, Sophora japonica or Helix pomotia lectins. Out of 14 different sugars, none interfered with the interaction between IgG Fc and membrane Fc gamma R. These results show that shed Fc gamma R had glucosyl, mannosyl, fucosyl and galactosyl groups, but that these components were not part of the IgG-binding site(s). The shed FcR had IgG-binding factor (BF) activity; it suppressed secondary in vitro antibody production. In accordance with the binding studies, IgG-BF activity could be adsorbed by ConA and PNA, but not by lentil lectins. The presence of 10 mM galactose or alpha-methylmannoside had no influence on biological activity, suggesting that, although present on human shed Fc gamma R, these sugars do not play a major role in its suppressive activity.

Antibody Formation↗