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At least 19 recordsLinked to original sources
PubMed1979

Induction of calcium flux across the rat mast cell membrane by bridging IgE receptors.

Rabbit antibody against IgE receptors or its F(ab')2 fragments induced an increase of 45Ca uptake into normal mast cells, and this process was accompanied by histamine release. Evidence was obtained that a substantial portion of 45Ca uptake was due to movement of calcium across the cell membrane. Neither 45Ca uptake nor histamine release was induced by Fab' monomer fragments of the antireceptor antibody. However, bridging of receptor-bound Fab' fragments by antirabbit IgG or bridging of receptor-bound IgE by anti-IgE induced an increase in 45Ca uptake. The results collectively indicate that crosslinking IgE receptors increases the membrane permeability of the mast cells toward calcium.

Animals↗
PubMed1979

Characterization of the IgE receptor isolated from human basophils.

The IgE receptor of human basophils was purified by using simple and repetitive affinity chromatography on human IgE-Sepharose. Basophils were partially purified from peripheral blood of patients with chronic myelogenous or basophilic leukemia. Cells were labeled with 125I by using the lactoperoxidase method and were solubilized with nonionic detergent. Elution of IgE-Sepharose with 0.5 N acetic acid, 1% NP-40 allowed recovery of active IgE receptor. Analysis of human IgE receptor by SDS polyacrylamide gel electrophoresis with 10% gels demonstrated one major radioactive peak with an apparent m.w. of 58,000 to 68,000, somewhat larger than rat IgE receptor. The purified human IgE receptor was active since approximately 10 to 42% of labeled receptor could specifically rebind to insolubilized human IgE. Rebinding was blocked by nanomolar concentrations of soluble human IgE or rat IgE but not by human or rat IgG, heat-inactivated human IgE, or heat-aggregated human IgG; thus it appears that rat IgE receptor. The relative abilities of active rat IgE and active human IgE to inhibit human IgE receptor rebinding could not be precisely determined because of the limitations in assessing the proportion of human IgE that retains receptor-binding activity.

Animals↗
PubMed1978

Triggering of histamine release from rat mast cells by divalent antibodies against IgE-receptors.

Antibodies against receptor molecules for IgE on rat basophilic leukemic (RBL) cells were prepared by immunization of a rabbit with immune precipitates composed of IgE-receptor complexes and anti-IgE. Antibodies against cell surface components were specifically purified by using RBL cells and rendered specific for mast cells by appropriate absorption. The major antibodies in the final preparation (anti-RBL) were directed against receptor molecules. It was found that the F(ab')2 fragments of anti-RBL induced histamine release from rat mast cells and caused immediate skin reactions in normal rats. These reactions by anti-RBL or its F(ab')2 fragments were inhibited if the receptors on mast cells had been saturated with IgE. The Fab' fragments of anti-RBL could bind with receptors on RBL cells and blocked passive sensitization of mast cells with IgE antibodies, but failed to induce skin reactions and histamine release from normal mast cells. Sensitization of normal rat skin with the Fab' fragment followed by an i.v. injection of anti-rabbit IgG induced skin reactions. The results indicated that bridging of receptor molecules by divalent anti-receptor antibody triggered mast cells for histamine release.

Animals↗
PubMed1978

IgE receptors on human basophils. Relationship to serum IgE concentration.

As reported previously, and confirmed here in 26 donors, the serum IgE level (2.6-5,500 ng/ml) correlates well (rs = 0.95, P less than 0.001) with the in vivo number of IgE molecules/basophil (6,000-600,000). The total number of IgE receptors/basophil was monitored by incubating them with an IgE-rich serum (15 microgram/ml), quantitatively stripping IgE from the cells at pH 3.7, and measuring eluted IgE by a direct radioimmunosorbent test. Saturation of receptors for each donor was achieved with 15 nM IgE (3 microgram/ml). The proportion of receptors occupied in vivo correlated with the serum IgE (rs = 0.84, P less than 0.001) whereas the average association constant of the receptors was independent of serum IgE and ranged from 7.1 X 10(8)/M to 2.8 X 10(10)/M, averaging 7.7 X 10(9)/M. Unexpectedly, the total number of IgE receptors/basophil was closely related to the serum IgE level. (rs = 0.92, P less than 0.001). Thus, either there is genetic association between serum IgE and the number of basophil IgE receptors, or, more likely, the receptor number is modulated by the serum IgE concentration.

Basophils↗
PubMed1979

Relationship between histocompatibility antigens, other surface determinants and the IgE receptor on rat mast cells.

Rat alloantibodies recognizing classical transplantation antigens (CTA) or non-H-1 determinants were able to compete effectively with monomeric IgE or IgG-coated sheep erythrocytes for receptor sites on the rat mast cell surface. Inhibitory capacity, however, was entirely confined to anti-CTA antibodies of the IgG2a subclass, whereas IgG1 antibodies lacked this ability. Analogously, F(ab')2 fragments of anti-CTA antibody consistently failed to affect IgE binding, but exposure of cell-bound F(ab')2 to anti-rat IgG restored its inhibitory capacity. From these results it was concluded that receptor sites recognizing the Fc portion of the anti-CTA molecule are involved in the inhibition process. Based on a cytotoxicity assay and on comparative absorption studies on alloantisera, the existence and relative amount of CTA and I region-associated antigens on purified rat mast cells and lymph node cells were analyzed. Whereas the CTA concentration per unit surface area on both cell types was very similar, rat mast cells consistently lacked Ia antigens.

Absorption↗
PubMed1976

The rat basophilic leukemia cell receptor for IgE. I. Characterization as a glycoprotein.

Rat basophilic leukemia cells were labeled either enzymically with 125I or biosynthetically by culture in the presence of 14C-glucosamine or 3H-amino-acids and then extracted with NP-40. IgE-anti-IgE precipitates insolubilized a radiolabeled macromolecule from these extracts largely or entirely absent in control IgG-anti-IgG percipitates. When specific precipitates were boiled in sodium dodecyl sulfate (SDS) and analyzed by polyacrylamide gel electrophoresis in the presence of SDS, most of the 14C or 125I radioactivity was in the area corresponding to an apparent m.w of 60,000 to 70,000 in 5.9% gels. In 10% and 12% gels, faster mobility was demonstrated indicating an atypical electrophoretic behavior often associated with glycoproteins and a presumptive m.w. of 50,000 or less. Since only IgE-containing precipitates localized label in this region and since such precipitates from cells saturated with IgE prior to surface iodination failed to show this band, the labeled macromolecule appears to be the IgE receptor itself. Analysis of the acid hydrolysates of precipitated 14C radioactivity demonstrated that label was entirely in hexosamines and sialic acid. 125I and 14C labels in the recepotr region were eliminated almost completely with pepsin and pronase and to a lesser extent with trypsin.

Animals↗
PubMed1979

Lymphocytes bearing Fc receptors for IgE. II. Induction of Fcepsilon-receptor bearing rat lymphocytes by IgE.

The proportion of lymphocytes bearing receptors for IgE (FcepsilonR) markedly increased after infection of rats with Nippostrongylus brasiliensis (Nb). The FcepsilonR-bearing lymphocytes from the infected animals bound more IgE-coated erythrocytes in rosette assay than FcepsilonR-bearing cells from normal rats, suggesting that the number of FcepsilonR per cell may also increase following the infection. In contrast, the number of IgE-receptors on peritoneal mast cells did not change after Nb infection. The increase in the proportion of FcepsilonR-bearing lymphocytes in Nb-infected rats is probably due to an increased concentration of IgE in the environment. The proportion of FcepsilonR-bearing cells in normal rat lymphocyte suspensions increased by culture of the cells with rat IgE of 1 microgram/ml or higher concentration. Other immunoglobulins such as rat IgG, human IgE, or rabbit IgG failed to induce either FcepsilonR-bearing cells or FcgammaR-bearing cells. It was also found that induction of Fc receptors by rat IgE is confined to FcepsilonR. Kinetic studies on the induction of FcepsilonR-bearing lymphocytes in vitro showed that the proportion of these cells in lymphocyte suspensions increased within 8 hr incubation with rat IgE but not within 4 hr. Evidence was obtained that both RNA synthesis and protein synthesis, but no DNA synthesis, are required for the induction of FcepsilonR-bearing cells or the expression of the receptors on the cell surface.

Animals↗
PubMed1978

Triggering of cultured neoplastic mast cells by antibodies to the receptor for IgE.

Cell surface receptors for IgE were isolated from detergent lysates of iodinated, IgE-saturated, rat basophilic leukemia cells by precipitation with anti-IgE antibodies followed by chromatography at acid pH. The isolated material showed a single 125I-band (m.w. approximately 58,000) on gel electrophoresis in sodium dodecyl sulfate and was used to immunize a rabbit. The resulting anti-serum was reacted with lysates of surface iodinated mouse or rat tumor mast cells. Analysis of the precipitates on (10%) gel electrophoresis revealed one major peak comprising greater than 80% of the detectable counts and having an estimated m.w. of approximately 58,000. The antiserum reacted with detergent-solubilized and cell-bound receptors in the presence or absence of excess IgE; it also inhibited the binding of 125I-IgE. Cultured mouse mastocytoma cells never exposed to IgE released 3H-serotonin when incubated with F(ab')2, but not Fab' fragments of the antiserum, which had been rigorously freed of IgE and anti-IgE. The release was inhibited in the presence of excess IgE, was Ca++ dependent, and equaled 80% of the maximum obtained with IgE and anti-IgE. We conclude that aggregation of the receptors for IgE provides the critical signals for cell activation.

Animals↗
PubMed1976

Antisera to mast cells and the receptor for IgE.

Recent studies on the receptor for IgE on rat mast cells and rat basophilic leukemia cells have established that this receptor has a molecular weight of about 60,000 daltons and is, at least in part, a protein. However, so far no antisera, monospecific for this receptor, are available. Only antisera to mast cells have been described. Such antisera are capable of releasing histamine from mast cells, but only in the presence of complement. In most instances such antisera were not specific for mast cells only, but in some cases they were rendered specific by absorption with lymph node cells or liver cells. One report demonstrates that such an absorbed antiserum was capable of inhibiting the binding of IgE to mast cells. Moreover, it precipitated several mast cell surface components. One of these possibly was the receptor for IgE.

Animals↗
PubMed1977

Failure of the putative IgE pentapeptide to compete with IgE for receptors on basophils and masts cells.

We have examined the claim that a pentapeptide resembling a portion of epsilon-chain of IgE can inhibit allergic reactions by competing with IgE for basophil-mast cell IgE receptors. Four laboratories with expertise in different areas collaborated. The following was found. (1) There was no evidence, by autoradiography, that the pentapeptide could block IgE fixation to basophils or displace IgE from these cells. (2) There was no evidence, by histamine release studies that the pentapeptide could block basophil sensitization or remove IgE from actively sensitized cells. The pentapeptide, also, did not impair antigen-induced histamine release. (3) There was no evidence that the pentapeptide could block the skin test response in Prausnitz-Küstner testing with the antigen injected intradermally or orally administered. Neither the correct pentapeptide sequence from the epsilon-chain nor the Fc" fragment of IgE impaired the P-K test. In each series of experiments, IgE myeloma protein, as a positive control, blocked the allergic response. The failure of the pentapeptide to block these reactions was observed at molar ratios of pentapeptide/IgE of 10(6) to 10(7). Our results, therefore, provide no evidence for competition between the pentapeptide and IgE. Even if there should be some weak affinity between the pentapeptide and IgE receptors on basophils or mast cells this would, by virtue of quantitative considerations, be of no clinical relevance.

Autoradiography↗
PubMed1979

Characterization of human lymphocytes bearing Fc receptors for IgE isolated from blood and lymphoid organs.

Human lymphocytes isolated from adult peripheral blood and cord blood, tonsils, adenoids and spleens were analysed for Fc receptors for IgE (Fcepsilon) by rosette assays. The Fcepsilon+ cells were also characterized for their class of surface immunoglobulin (sIg), complement receptors, receptors for sheep erythrocytes (E), and Helix pomatia A haemagglutinin (HP), and their abilities to phagocytoze and adhere. The average number of Fcepsilon+ cells was in adult peripheral blood 1.2 +/- 0.4%, in cord blood 3.0 +/- 1.3%, in tonsils 4.2 +/- 5.2%, in adenoids 5.8 +/- 4.2%, and in spleens varied from 0.8% to 15.8% among individual patients. Overnight culturing of the lymphocytes under conditions that allowed detection of Fc receptors for IgM (Fcmu) usually lowered the number of Fcepsilon+ cells. Neuraminidase treatment caused no change. Rosette formation was inhibited by IgE myeloma proteins and their Fc fragments, but not by mildly reduced and alkylated and heated (56 degrees C) IgE, indicating that the receptors are specific for the native configuration of the IgE Fc fragment. Double cell surface marker analyses with fluoresceinated F(ab')2 fragments of purified anti-mu, delta, and gamma antibodies used to label the Fcepsilon rosette-forming lymphocytes from peripheral adult and cord blood showed that 50-80% were sIgM+ but only 0-28% were sIgD+. In contrast, approximately 80% of the Fcepsilon+ cells from tonsils, adenoids and spleens were sIgM+ and sIgD+. The Fcesilon+ lymphocytes represented 10-20% of the sIgM+ lymphocytes in both the peripheral adult and cord blood. Depletion and enrichment experiments indicated that most of the Fcepsilon+ cells bear complement receptors. Lymphocytes having both E and Fcepsilon receptors were not found. Furthermore, the lymphocytes with HP receptors, a marker for T cells and immature B cells, were Fcepsilon-. Monocytes and neutrophil granulocytes did not form Fcepsilon rosettes. These data indicated that a minor population of human B lymphocytes have Fcepsilon receptors. The majority of the Fcepsilon+ lymphocytes in the blood differ from those in tonsils, adenoids and spleen in that the majority of the former are sIgM+/sIgD- and the latter sIgM+/sIgD+. The sIgM+/sIgD- Fcepsilon+ cells in the blood are probably relatively mature lymphocytes since they lacked HP receptors, which are found on immature B cells.

Cell Separation↗
PubMed1978

Differences in binding affinity of human IgE for receptors in chopped human lung.

Experiments were performed to ascertain whether IgE in different allergic sera had the same or different sensitizing properties for chopped human lung. When allergic sera were allowed to compete with myeloma IgE for tissue receptors in chopped lung and subsequently challenged with antigen, two groups of sera could be distinguished, one which competed well with myeloma IgE and one which competed poorly. Sera that competed well with myeloma IgE were also able to sensitize for greater histamine release relative to IgE concentration when sensitized lung tissue was challenged with anti-IgE. The converse was true of those sera that competed poorly with myeloma IgE in the antigen assay, in that they sensitized for histamine release only at relatively high IgE concentrations in the anti-IgE assay. The possible significance of these findings is discussed.

Antibody Affinity↗