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Biomedical subjects

J Gergely

Publications and source records attributed to J Gergely.

At least 163 records · Page 9Linked to original sources
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 distance between the high affinity sites of troponin-C measured by interlanthanide ion energy transfer.

Trivalent lanthanide ions are known to be good substituents for Ca2+ at all four calcium-binding sites of rabbit skeletal troponin-C (TnC). In particular, the visible luminescence of terbium ions bound at the two high affinity sites can be excited via a tyrosine residue. We have carried out energy transfer measurements using Tb3+ as the donor and a number of lanthanide ions as acceptors in order to measure the distance between the two high affinity sites in TnC. Luminescence decay measurements showed that, in the absence of acceptors, TnC-bound Tb3+ decays with a single lifetime of 1.31 ms. In the presence of a good acceptor such as Nd3+, the decay was resolvable into two components of roughly equal amplitude. The first was the same in lifetime as that of TnC-bound Tb3+ alone; the second has a shorter lifetime, presumably due to interlanthanide ion energy transfer. From these lifetimes and published critical transfer distances (Horrocks, W. DeW., Jr., Rhee, M.-J., Snyder, A.P., and Sudnick, D.R. (1980) J. Am. Chem. Soc. 102, 3650-3652), we obtained a distance of 0.92 nm between the two high affinity sites. This distance is consistent with the fact that the two high affinity sites have been located in the COOH-terminal half of TnC and with the proposal that each half of TnC is homologous in structure to parvalbumin (Kretsinger, R. H., and Barry, C. D. (1975) Biochim. Biophys. Acta 405, 40-52).

Animals↗
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

Changes in the lateral ordering of the macrophage plasma membrane during Fc receptor mediated phagocytosis.

The macrophage plasma membrane was labelled with an intercalated 5-doxyl stearic acid spin probe, and structural changes induced by IgG-coated erythrocytes (EA) were followed with particular emphasis on the possible role of lipid reordering in the sequential events of phagocytosis. We present three lines of experimental evidence to show that these structural changes were induced by the lateral aggregation of cell surface Fc receptors. Cytochalasin B, an inhibitor of microfilament function, blocked this membrane reordering; if it was added after EA binding induced membrane reordering had already been detected for 15 min, a rapid reversal process was observed resulting in a reversible restoration of the initial order parameter value. We suggest that these structural changes indicate lipid-lipid lateral phase separation, in line with morphological findings.

Animals↗
PubMed1982

Recognition of autologous and allogeneic lymphocytes and tumor cells by human natural killer cells.

The shedding of the mobile Fc receptor (FcR1) and the depletion of the immobile Fc receptor (FcR11) bearing human lymphocytes revealed that human natural killer cells belong to the FcR11-bearing population. Anti-beta-2-microglobulin treatment of the effector cells decreased natural cytotoxicity against some target cells and the detectability of HLA antigens, indicating that histocompatibility antigens or related structures may be involved in natural cytotoxicity. Using a panel of 29 autologous and allogenic PHA-stimulated target cells and peripheral lymphocytes from the same donors as the effector cells, distinct cytotoxic responses against allogeneic and autologous target cells were observed. A computer analysis of selective natural cytotoxicity distinguished seven different groups of target cells that may represent common structures for NK recognition.

Cell Line↗
PubMed1982

Complement-mediated fragmentation of soluble and insoluble immune complexes containing porcine anti-DNP antibodies.

Complement-mediated release of soluble immune complexes and immune precipitates containing DNP-PSA and precipitating or non-precipitating porcine anti-DNP antibodies was studied. A decrease in the average size of soluble immune complexes indicating their fragmentation was observed during incubation in excess human serum, the extent of the complex release was found to be in direct proportion to the time of incubation. The effect was complement-dependent. In the second part of the study, complement-dependent solubilization of the immune precipitates of the precipitating antibody preparation was compared to the solubilization of the precipitates of the non-precipitating antibody formed in the presence of PEG. Although, both types of precipitates activated complement in about the same extent, complexes of non-precipitating antibody were solubilized much slower than those of the precipitating one. As avidity of both antibody preparations to the antigen was high, the observed differences in the rate of the complex solubilization probably reflected differences in the structure of the two types of complexes.

Animals↗
PubMed1982

Serial measurement of circulating immune complexes in healthy subjects.

Circulating immune complex (CIC) levels were serially studied in healthy subjects and in normal rats. In human 3 methods (Clq solubility, complement consumption, and granulocyte phagocytosis tests) were used for the measurement of CIC; in rats, CIC levels were determined by the modified complement consumption test. A marked fluctuation in the CIC level was observed both in healthy human subjects and in normal rats. No correlation between results of the 3 assays used for CIC detection was found indicating that not only the level but the composition of CIC changes continuously in health.

Animals↗
PubMed1982

Metal-binding properties of calmodulin.

Metal-binding properties of calmodulin have been studied by using trivalent lanthanide ions as analogs of Ca2+. In agreement with a report published as this work was in progress [Kilhoffer, M.-C., Demaille, J. G., and Gerald, D. (1980) FEBS Lett. 116, 269-272] we found that sites I and II are the high-affinity sites, while sites III and IV are the low-affinity sites for Tb3+. Competition experiments suggest the same preference in binding also applies to Ca2+. With calmodulin selectively nitrated at either of the two tyrosine residues we found that, although both tyrosine groups can transfer energy to the bound Tb3+, the fluorescence of only Tyr-138 is sensitive to metal binding. Direct excitation of bound Eu3+ ions using a laser indicates that all four sites possess very similar microenvironments. These studies demonstrate that the binding properties of calmodulin are different from those of the homologous protein troponir C.

Binding Sites↗
PubMed1982

Binding of different ligands to IgM-Fc receptors of rat leucocytes.

The primary receptor ligand interaction between rat leucocyte membrane receptors for IgM and their ligands were examined. We found that the incubation time for optimal IgM binding is different on the two types of IgM-Fc receptor-bearing spleen cells and peritoneal macrophages. The investigation of cytophilic activity of polyclonal or monoclonal IgM proteins and their fragments from various species indicated the fine specificity of receptors. Finally, data are presented which suggest a multiple point co-operative binding between IgM-coated erythrocytes and IgM-Fc receptor-bearing cells.

Animals↗
PubMed1982

Immunogenicity of antigen complexed with antibody. I. Role of different isotypes.

IgM-, IgG1-, IgG2a-, IgG2b- and IgE-type anti-ovalbumin antibodies were isolated from rat immune sera and the complexes formed by antibodies of a defined isotype and the antigen were compared for antibody avidity and interaction with homologous complement. IgG2a-containing complexes consumed total complement with the greatest efficiency. IgG2a-, IgG2b- and IgM-containing complexes displayed similar activities in activation of the alternative pathway while IgG1 was less efficient. Reduction and alkylation of IgG2a antibodies abolished the capacity of the complex to activate the alternative pathway, but not their total complement consumption. The complement-dependent solubilization was greatest when complexes contained IgG1- or IgM-type antibodies and lowest with IgG2a-containing complexes. Inbred Long Evans rats immunized by complexes containing IgG1 or IgG2b antibodies displayed a markedly lower delayed-type hypersensitivity (DTH) compared with those immunized by antigen alone. Immunization with IgG2a- or IgE-containing complexes resulted in a slightly decreased DTH, while IgM-containing complexes induced DTH like ovalbumin alone. IgG2a-containing complexes elicited an antibody response markedly higher than that found in animals immunized by antigen alone. The same effect was found when complexes contained reduced-alkylated IgG2a. Immunization with complexes containing the other isotypes involved in the study induced an antibody response similar to the antigen in phosphate-buffered saline.

Alkylation↗
PubMed1981

Proteolytic fragments of troponin C. Interactions with the other troponin subunits and biological activity.

Fragments of rabbit skeletal muscle Ca2+-binding subunit of troponin (TnC), obtained by cleavage with trypsin, thrombin, and CNBr, were tested for their ability to form binary and ternary complexes with ATPase inhibitory subunit (TnI) and tropomyosin-binding subunit (TnT) and their ability to replace TnC in reversing TnI inhibition of actomyosin ATPase activity. Three regions of TnC were found to be involved in interaction with TnI. Regions near Ca2+-binding sites II and III require Ca2+ for the interaction, while a third region near Ca2+-binding site IV binds TnI whether or not Ca2+ is present. The TnT binding site has been localized in the NH2-terminal half of TnC. Several of the TnC fragments form soluble ternary complexes with TnI and TnT. Fragments that contain amino acid residues 89-100 and at least one pair of Ca2+-binding sites are able to reverse the TnI inhibition of actomyosin ATPase activity, which exhibits the same [Ca2+]1/2 regardless of which of the Ca2+-binding sites are present in the fragment.

Actomyosin↗
PubMed1981

Binding of lanthanide ions to troponin C.

Tb3+ and Eu3+ bound to troponin C were detected by (1) changes in the fluorescence of the tyrosine chromophore of the protein or (2) the luminescence of the ions themselves excited by energy transfer from the protein or by direct excitation using a pulsed laser light source [Horrocks, W. DeW., Jr., & Sudnick, D. R. (1979) Science (Washington, D.C.) 206, 1194-1196]. Titrations carried out in the absence and presence of Ca2+ suggest two classes of binding sites (two sites in each class) for the lanthanides, corresponding to the high- and the low-affinity sites for Ca2+. Computer analysis, assuming competition between Ca2+ and the lanthanide, using the binding constants of Ca2+ for TnC [Potter, J. D., & Gergely, J. (1975( J. Biol. Chem. 250, 4628-4633] yields 5.2 X 10(8) M-1 and 9.7 X 10(6) M-1 for Tb3+ and 4.7 X 10(9) M-1 and 5.3 X 10(7) M-1 for Eu3+, for the high- and the low-affinity sites, respectively. From lifetimes of laser-induced luminescence in H2O and in D2O, the number of water molecules coordinated to Eu3+ was two at the high and three at the low affinity sites.

Animals↗