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M Daëron

Publications and source records attributed to M Daëron.

At least 73 records · Page 4Linked to original sources
PubMed1987

Induction of Fc receptors for IgA on murine T cell hybridoma by human monoclonal IgA and by high molecular weight IgA in IgA nephropathy.

A reproducible immunocyto-adherence assay has been developed to study the modulation of Fc receptors for IgA (Fc alpha R), using a murine T cell hybridoma (T2D4), which expresses Fc receptors for all known isotypes of secreted immunoglobulins. By using sheep red blood cells coated with the hapten 2-4-6 trinitrophenyl (TNP), as indicator cells, and a murine monoclonal IgA (MOPC 315) antibody with anti-TNP activity, we were able to study the Fc alpha R on T2D4 cells. We found that: (a) murine Fc alpha R can bind human monoclonal IgA, and this binding is isotype specific since it was inhibited by human monoclonal IgA but not by human monoclonal IgG or IgM; (b) the expression of murine Fc alpha R is unducible by human monoclonal IgA, and this effect is isotype specific since it is not observed with human monoclonal IgM or IgG (c) sera from patients with IgA nephropathy can also induce Fc alpha R expression; by contrast, no induction was observed with normal human sera, (d) in one serum from an IgA-nephropathy patient, the inducer factor was characterized by affinity chromatography on anti-IgA-Sepharose and by gel filtration: high molecular weight IgA, probably IgA aggregates or immune complexes were recognized to be responsible for the induction of murine Fc alpha R expression.

Animals↗
PubMed1986

Size and charge heterogeneity of murine IgG-binding factors (IgG-BF).

Size and charge of murine IgG-binding factors (IgG-BF) were determined. Four different sources were used to produce the factors: a) cells of a T cell hybrid (T2D4) constitutively secreting IgG-BF upon incubation in serum-free medium, b) T2D4 cells incubated with mouse monoclonal IgG1 antibody in order to induce in vitro the production of isotype-specific IgG1-BF, c) T2D4 cells induced in vivo by passage as ascites in nude mice and incubated in serum-free medium, and d) in vivo alloantigen-activated T cells (ATC) incubated in serum-free medium. IgG-BF were affinity purified on Sepharose beads coated with rabbit or mouse IgG and identified by their biologic activities, i.e., inhibition of in vitro secondary IgG antibody production to SRBC and inhibition of rosette formation between Fc gamma receptor-positive spleen cells and rabbit IgG-sensitized erythrocytes. IgG-BF produced by either of these cell sources was found to be heterogeneous in both size and charge. In each case, IgG-BF activities were recovered in three fractions of apparent Mr-74,000 to 78,000, 35,000 to 40,000, and 19,000 to 23,000-and in four fractions of pI-4.7 (or 5.3, depending on experimental conditions), 6.5, 7.7, and 8.4. Moreover, IgG-BF translated in vitro from T2D4 poly A RNA by using rabbit reticulocyte lysate exhibited the same heterogeneity. Thus, IgG-BF contain different proteins exerting similar biologic activities.

Animals↗
PubMed1986

2.4G2, a monoclonal antibody to macrophage Fc gamma receptors, reacts with murine T cell Fc gamma receptors and IgG-binding factors.

In order to determine whether T cell Fc gamma receptors (Fc gamma R) and IgG-binding factors (IgG-BF) are structurally related, we searched for common antigens on these molecules. We found that the anti-macrophage Fc gamma 1/gamma 2bR monoclonal antibody 2.4G2 binds to similar determinant(s) on the macrophage-like J774 cells and on the Fc gamma R+ hybridoma T cells T2D4. On the T cell membrane, these determinants are associated with Fc gamma 1/gamma 2bR. They are absent on Fc gamma R- hybridoma T cells or the FcR- BW5147 thymoma cells. 2.4G2-reactive molecules were also detected in soluble material either extracted or released in the supernatant of Fc gamma R+ hybridoma T cells. 2.4G2-reactive molecules released in the supernatant of T2D4 cells could be absorbed on Sepharose beads coupled to rabbit IgG and they were recovered by acid elution. Conversely, Sepharose beads coupled to 2.4G2 retained molecules which had affinity for rabbit IgG, which suppressed an in vitro antibody response and which had the same molecular weight as IgG-BF. These results indicate that T cell Fc gamma R and IgG-BF share common epitopes and that 2.4G2 can serve as an anti-IgG-BF antibody.

Animals↗
PubMed1986

Identification of antibody classes and Fc receptors responsible for phagocytosis of Trypanosoma musculi by mouse macrophages.

The phagocytosis of Trypanosoma musculi by macrophages in the presence of specific antibodies was investigated. In 14-day-infected mice, opsonic antibodies were detected in serum, and phagocytosis of parasites by peritoneal macrophages was observed. The mechanism of T. musculi phagocytosis was analyzed. The binding of trypanosomes to peritoneal macrophages and J774 cells was observed in the presence of serum from hyperimmune mice and from mice infected 14 or 28 days earlier, but not in the presence of control mouse serum or sera from 7-day-infected mice. Binding was partially inhibited by mouse monoclonal immunoglobulins G1 (IgG1) or IgG2a and almost completely inhibited by a mixture of both. Binding was also partially inhibited by the anti-Fc gamma 1/gamma 2b receptor monoclonal antibody 2.4G2. Binding of T. musculi was also induced by fractions of serum from 28-day-infected mice obtained by protein A-Sepharose chromatography. Only the IgG1-rich fraction eluted at pH 6.0 and the IgG2a-rich fraction eluted at pH 4.5 promoted binding which could be almost completely inhibited by monoclonal IgG1 and IgG2a. These data indicate that IgG1 and IgG2a anti-T. musculi antibodies are responsible for the phagocytosis of T. musculi by mouse macrophages and both Fc gamma 2a and Fc gamma 1/gamma 2b receptors are involved. Such a mechanism is likely to account for the elimination of parasites in T. musculi-infected mice.

Adhesiveness↗
PubMed1985

Receptors for immunoglobulin isotypes (FcR) on murine T cells. I. Multiple FcR expression on T lymphocytes and hybridoma T cell clones.

T cell receptors for the Fc portion of the various isotypes of mouse immunoglobulins (FcR) were examined by rosette formation, using as indicator cells erythrocytes coated with monoclonal antibodies of all known isotypes of serum immunoglobulins. Three populations of mouse T cells were studied: normal thymocytes, activated T cells (ATC), generated by educating thymocytes in lethally irradiated allogeneic hosts, and hybridoma T cells, derived from somatic hybridization of ATC with the FcR-negative thymoma BW.5147. We found that many different FcR could be distinguished by their specificity for a single isotype or for a combination of several isotypes; ATC and hybridoma T cells expressed several such receptors that, at least in cloned cells, could be demonstrated to be borne by individual cells; hybridoma T cells of independent origin bore indistinguishable receptors whereas ATC expressed markedly different FcR and upon overnight incubation at 37 degrees C, immunoglobulins were found to bind onto the cell surface, even though no corresponding constitutive FcR was detected. The same was observed with hybridoma T cells and with thymocytes. It follows that a single T cell can express several FcR. Altogether, these FcR are capable of binding all known isotypes of serum immunoglobulins. They differ from one T cell to another.

Animals↗
PubMed1985

Receptors for immunoglobulin isotypes (FcR) on murine T cells. II. Multiple FcR induction on hybridoma T cell clones.

In the preceding report (Eur. J. Immunol. 1985. 15: 662), we described a variety of receptors for the Fc portion of the different isotypes of mouse immunoglobulins (FcR), that were found to be expressed on hybridoma T cell clones. In the present work, we wondered whether the expression of these T cell FcR would be regulated by environmental influences such as the presence of corresponding ligands. We found that exposing the cells to the bulk of serum immunoglobulins in vivo, or to purified monoclonal immunoglobulins in vitro both resulted in FcR induction. The expression of all constitutive receptors, i.e. Fcgamma 1/2bR, Fcgamma3R, FcalphaR and FcepsilonR, could be increased upon incubation with IgG1, IgG2b, IgG3, IgA and IgE, respectively. After induction, the specificity of FcR was not modified. Two FcR were detectable only upon induction. These were Fcgamma2a/2b/1R, induced by IgG2a and FcmuR, induced by IgM. Interestingly, FcR detectable after induction only were short-lived at the membrane. Ten to 15 h after induction they were not detected any more, whereas the expression of constitutive FcR remained elevated for at least 24 h following induction. Therefore, depending on the concentration of immunoglobulins in the environment, and depending on whether they are short lived or long lived, FcR can modulate their expression on the membrane of T cells. Such a versatility might be an efficient means to contribute to isotypic regulation through the release of regulatory immunoglobulin-binding factors. factors.

Animals↗
PubMed1982

Biochemical analysis of glucocorticoid-induced inhibition of IgE-mediated histamine release from mouse mast cells.

Pretreatment of mouse mast cells with 10(-7) to 10(-6) M dexamethasone (DM) during overnight sensitization with mouse IgE antibody resulted in inhibition of antigen-induced histamine release and degranulation. The inhibition of both degranulation and histamine release increased linearly with the duration of the treatment; maximal inhibition was obtained after approximately 16 hr with DM. The addition of DM to sensitized mast cells immediately before antigen challenge did not affect the antigen-induced histamine release. DM interacted directly with mast cells by binding to DM-specific cytoplasmic receptors. The treatment of mast cells with DM did not affect the binding of IgE to mast cells or intracellular cAMP levels. Bridging of cell-bound IgE anti-DNP antibody on mouse mast cells either by multivalent DNP-HSA or by anti-IgE induced phospholipid methylation at the plasma membrane and Ca++ influx into the cells. Pretreatment of mast cells with DM inhibited the antigen-induced phospholipid methylation and Ca++ uptake but failed to affect histamine release by Ca++ ionophore A23187. The results suggest that DM treatment inhibits histamine release by the inhibition of the early stage of biochemical processes leading to opening Ca++ channels but does not affect the process distal to Ca++ influx or the binding of IgE molecules to IgE receptors.

Animals↗
PubMed1979

Mast cell membrane antigens and Fc receptors in anaphylaxis. I. Products of the major histocompatibility complex involved in alloantibody-induced mast cell activation.

Mast cell membrane antigens, coded by the K, I and D regions of the major histocompatibility complex of the mouse, were investigated for their presence at the cell surface and their participation in alloantibody-induced anaphylactic degranulation (DAAD). Anti-H-2 K, as well as anti-H-2 D antibodies were found to elicit DAAD. Recognition, on the mast cell membrane, of any product of the K or the D regions, either as the whole molecule, or as public or private antigens only, or even as a single private specificity, enabled alloimmune sera to trigger mast cell degranulation. By contrast, anti-Ia antibodies failed to elicit DAAD. By the autoradiographic technique, peritoneal mast cells were found to constitute a single homogeneous population, bearing H-2 D-coded antigens, although in smaller amounts than other peritoneal cells, but no Ia antigens or, if any, in much smaller amounts than other peritoneal cell type. These findings bring new evidence that mast cell alloantigens do participate in anaphylactic alloantibody-induced mast cell degranulation, by allowing bridging of (one?) Fc receptor with H-2 molecules.

Anaphylaxis↗
PubMed1976

An ultrastructural study of two different responses of mouse mast cells to transplantation antibodies directed against the same transplantation antigens.

The present paper describes an ultrastructural study of two different kinds of behavior of mouse mast cells during two immunological reactions induced by transplantation antibodies: the direct allogeneic anaphylactic degranulation and the serocytotoxicity. In both situations, the same alloantigens, born by the mast cells themselves, are the targets of the reaction, but the first one is mediated by anaphylactic alloantibodies whereas the second one is mediated by cytotoxic alloantibodies in the presence of complement. The comparison of the ultrastructural aspects of the cells in these two systems demonstrated that mast cells can behave in two different ways depending on the nature of the immunological agents utilized. First, a physiological degranulation process with active granule expulsion was observed. This process was shown to be identical to the one induced in classical in vitro anaphylaxis or by histamine releasers such as compound 48/80. A second type of behavior was a lethal, complement-dependent, cell lysis without active granule expulsion.

Anaphylaxis↗