SEARCH · PubMed Health

Results for “Basophil Degranulation Test”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

475 records · Page 27Linked to original sources

PubMed2002

Mutagenesis within human FcepsilonRIalpha differentially affects human and murine IgE binding.

Soluble fragments of the alpha-chain of FcepsilonRI, the high-affinity receptor for IgE, compete with membrane-bound receptors for IgE and may thus provide a means to combat allergic responses. Mutagenesis within FcepsilonRIalpha is used in this study, in conjunction with the crystal structure of the FcepsilonRIalpha/IgE complex, to define the relative importance of specific residues within human FcepsilonRIalpha for IgE binding. We have also compared the effects of these mutants on binding to both human and mouse IgE, with a view to evaluating the mouse as an appropriate model for the analysis of future agents designed to mimic the human FcepsilonRIalpha and attenuate allergic disease. Three residues within the C-C' region of the FcepsilonRIalpha2 domain and two residues within the alpha2 proximal loops of the alpha1 domain were selected for mutagenesis and tested in binding assays with human and mouse IgE. All three alpha2 mutations (K117D, W130A, and Y131A) reduced the affinity of human IgE binding to different extents, but K117D had a far more pronounced effect on mouse IgE binding, and although Y131A had little effect, W130A modestly enhanced binding to mouse IgE. The mutations in alpha1 (R15A and F17A) diminished binding to both human and mouse IgE, with these effects most likely caused by disruption of the alpha1/alpha2 interface. Our results demonstrate that the effects of mutations in human FcepsilonRIalpha on mouse IgE binding, and hence the inhibitory properties of human receptor-based peptides assayed in rodent models of allergy, may not necessarily reflect their activity in a human IgE-based system.

Animals↗

PubMed1990

The mechanism of mediator release from human basophils induced by platelet-activating factor.

Platelet-activating factor (PAF) is a lipid mediator able to induce a variety of inflammatory processes in human peripheral blood cells. We have investigated the effect of PAF on the release of chemical mediators from human basophils of allergic and normal donors. PAF (10 nM to 1 microM) caused a concentration-dependent, noncytotoxic histamine release (greater than or equal to 10% of total) in 27 of 44 subjects tested (24 atopic and 20 nonatopic donors). The release process was either very rapid (t1/2 approximately equal to 10 s) or quite slow (t 1/2 approximately equal to 10 min), temperature- and Ca2(+)-dependent (optimal at 37 degrees C and 5 mM Ca2+). Coincubation of PAF with cytochalasin B (5 micrograms/ml) enhanced the release of histamine induced by PAF and activated the release process in most donors (42 of 44). Atopics did not release significantly more histamine than normal subjects, and the percentage of PAF responders (greater than or equal to 10% of total) was nearly the same in the two groups. Histamine release was accompanied by the synthesis and release of leukotriene C4, although this lagged 1 to 2 min behind histamine secretion. Lyso-PAF (100 nM to 10 microM), alone or together with cytochalasin B, did not release significant amounts of histamine. The release of histamine activated by PAF was inhibited by the specific PAF receptor antagonist, L-652,731, with an IC50 of 0.4 microM. There was a partial desensitization to PAF when the cells were preincubated with PAF (100 nM to 1 microM) for 2 min in the absence of Ca2+, whereas the cells remained responsive to anti-IgE (0.1 micrograms/ml). If neutrophils were removed from the basophil preparation by a Percoll gradient or a countercurrent elutriation technique, there was a significant decrease in PAF-induced histamine release. PAF (1 microM) was able to induce a very rapid, transient rise (peak less than 10 s) in [Ca2+]i in purified basophils analyzed by digital video microscopy. Finally, among human histamine-containing cells, the basophils are unique in degranulating following a PAF challenge. Mast cells from human lung, skin, or uterus failed to respond to PAF (10 nM to 1 microM) regardless of the presence or absence of cytochalasin B (5 micrograms/ml). Our results demonstrate that PAF is able to induce the release of inflammatory mediators from human basophils, and that neutrophils can influence this response. It is suggested that PAF-induced basophil activation can play a role in the pathogenesis of allergic disorders.

Antibodies, Anti-Idiotypic↗

PubMed2005

Comparative potency of Ara h 1 and Ara h 2 in immunochemical and functional assays of allergenicity.

To assess the relative potency of the major peanut allergens, Ara h 1 and Ara h 2, we examined the relative ability of purified proteins to bind IgE on immunoblots, to cross-link allergen specific IgE in an in vitro assay of degranulation based on RBL SX-38 cells, and to bind IgE in the ImmunoCap assay. Sera from 12 highly sensitive, peanut allergic patients were studied in all assays. IgE immunoblots with crude peanut extracts showed binding of IgE to multiple bands including the 63 kDa and 17-19 kDa bands that contain Ara h 1 and Ara h 2, respectively. In the functional assay, Ara h 2 was more potent than Ara h 1 in 11 of 12 sera tested with a median potency that was 52.5-fold more than Ara h 1 (P < 0.005). Contrary to findings with the functional assay, IgE immunoblots with purified Ara h 1 and Ara h 2 showed substantially lighter binding of IgE to Ara h 2 compared with Ara h 1 (P = 0.02). The ImmunoCap assay gave intermediate results with slightly more IgE binding to Ara h 2 than to Ara h 1 (P = 0.005). In conclusion, Ara h 2 is a very potent allergen and is much more potent than Ara h 1 for most sera using an in vitro assay of IgE cross-linking and cell activation. This finding is different from what was predicted based on immunoblots or with the ImmunoCap assay.

2S Albumins, Plant↗

PubMed1994

Macrophage inflammatory protein-1 alpha and monocyte chemoattractant peptide-1 elicit immediate and late cutaneous reactions and activate murine mast cells in vivo.

We have previously reported that monocyte chemoattractant protein-1 (MCP-1) is the most potent histamine-releasing factor (HRF) for basophils. Macrophage inflammatory protein-1 alpha (MIP-1 alpha) has modest histamine-releasing activity. The objective of this study was to investigate whether MCP-1 and MIP-1 alpha would activate mast cells in vivo and induce a cutaneous inflammatory reaction in mice. To this goal, mouse hind footpads were separately injected with 20 microliters of human recombinant MCP-1 or MIP-1 alpha (10(-7) M). Diluent was used as a control in the second footpad. The footpad-swelling response was measured at 30 min, 1 h, and then hourly for 6 h. Both MCP-1 (2.72 +/- 0.2 vs 2.1 +/- 0.03 mm for diluent, n = 8, p < 0.02) and MIP-1 alpha (3.0 +/- 0.1 vs 2.1 +/- 0.03 mm for diluent, n = 8, p < 0.02) induced an immediate swelling reaction. The immediate reaction was followed by a sustained late reaction that peaked within 1 h and lasted for more than 6 h. Histologic examination of the footpads, obtained at hour 2, revealed that MCP-1 caused mild mononuclear cell infiltrates, moderate degranulation of mast cells, and soft tissue swelling. In contrast, MIP-1 alpha induced a severe inflammatory reaction that consisted of neutrophils, mononuclear cells, and degranulated mast cells. Electron microscope examination of the tissue revealed features of extensive mast cell degranulation by MIP-1 alpha and to a lesser extent by MCP-1. Thus, we conclude that mast cells are activated on injection of MCP-1, whereas degranulation of mast cells and recruitment of leukocytes contribute to the footpad reaction induced with MIP-1 alpha.

Animals↗

PubMed1995

Regulation of human interleukin-8 receptor A: identification of a phosphorylation site involved in modulating receptor functions.

The human type A interleukin-8 receptor (IL-8RA) was modified to express an amino-terminal epitope tag and stably overexpressed in a rat basophilic leukemia cell line (RBL-2H3). This receptor (ET-IL-8RA) displayed functional properties similar to those of the native receptor in neutrophils in that exposure to IL-8 stimulated GTPase activity, phosphoinositide (PI) hydrolysis, intracellular calcium mobilization, and degranulation in a pertussis toxin (PTx) susceptible fashion. IL-8 induced dose- and time-dependent phosphorylation of ET-IL-8RA. Phorbol 12-myristate 13-acetate (PMA) treatment also resulted in phosphorylation of the receptor although to a lesser extent. Staurosporine totally blocked PMA-induced phosphorylation but only partially inhibited IL-8-mediated phosphorylation. Phosphorylation of ET-IL-8RA correlated with its desensitization as measured by GTPase activation and calcium mobilization. To determine the role of phosphorylation in IL-8RA signal transduction, three mutants lacking specific serine and threonine residues located at the C-terminal of this receptor were constructed by site-directed mutagenesis (M1, M2, and M3). The mutated receptors expressed in RBL-2H3 cells displayed pharmacological properties (Kd approximately 2-2.8 nM and Bmax approximately 3-3.5 pmol/mg of protein) similar to those of the wild-type ET-IL-8RA. M2 and M3, but not M1, showed a marked decrease in IL-8-induced phosphorylation compared to the wild-type receptor. M2 and M3 but not M1 were resistant to PMA-mediated phosphorylation and desensitization and were also more resistant to homologous desensitization than M1 or ET-IL-8RA.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗

PubMed1995

Expression and function of fibronectin binding integrins on rat mast cells.

Adhesion molecules of the integrin family are implicated not only in leukocyte migration but also in leukocyte activation. Here we characterize the expression and function of fibronectin receptor integrins on rat mast cells. A rat basophilic leukemia cell line (RBL-2H3) and phorbol ester-stimulated rat peritoneal mast cells adhered to fibronectin (FN), vitronectin and fibrinogen. These mast cells expressed fibronectin receptor integrins, including very late antigen (VLA)-4, VLA-5 and vitronectin receptor (VNR), as estimated by immunofluorescent staining and inhibition of FN adherence by newly established mAbs reactive with the rat alpha 4 (MR alpha 4-1), alpha 5 (HM alpha 5-1) or beta 3 (HM beta 3-1) chains of the integrin molecules. The beta-hexosaminidase release, a marker for mast cell degranulation, triggered by high affinity IgE receptor (Fc epsilon RI)-mediated stimulation, was enhanced by adhesion of RBL-2H3 cells to either immobilized FN, MR alpha 4-1, HM alpha 5-1 or HM beta 3-1. This FN enhancement of beta-hexosaminidase release was inhibited by soluble MR alpha 4-1, HM alpha 5-1 and HM beta 3-1 as well as by GRGDSP and DELPQLVTLPHPNHLGPEILDVPST peptides which abrogate VLA-5/VNR and VLA-4 binding to FN respectively. In vivo, passive cutaneous anaphylaxis induced by IgE anti-DNP and DNP-BSA was inhibited by concurrent s.c. injection of MR alpha 4-1, HM alpha 5-1 and HM beta 3-1. These results demonstrate that FN receptor integrins expressed on rat mast cells play an important role in regulating mast cell activation both in vitro and in vivo.

Amino Acid Sequence↗

PubMed1998

[An attempt to block histamine release from basophils granulocytes with antibodies obtained as a result of long-term immunization].

UNLABELLED: Pathogenetic mechanisms responsible for efficacy of specific immunotherapy still remain to be fully explained. This concerns both desensitization with classic allergens and very rarely used specific immunotherapy with bacteria. Microbes can play important role as hypersensitivity factor in some allergo-inflammatory processes. Bacterial products may act as basophil histamine liberators through immunological (IgE-mediated) and nonimmunological--particular lectin-sugar way. The aim of study was to verify if histamine release triggered by microbes could be modified (blocked) with specific antibacterial antibodies--taking into consideration both of mechanisms of basophil degranulation. The size of immediate (in healthy persons--Tab. 3, 4) and late as well as delayed (in asthmatic patients--Tab. 8) skin reactivity to examined microorganisms and the degree of basophil histamine release induced with these bacteria were compared. Human basophils were isolated from peripheral blood on Ficoll-Hypaque gradient, next challenged with whole, formalin-killed bacteria and with the same bacteria after incubation with specific and nonspecific sera. To differentiate between IgE-dependent and non-immunological mechanisms of histamine release, the IgE molecules were removed from the surface of the basophils by exposure to pH 3.6 (stripping). In each experiment histamine release induced by anti-IgE antibodies was used as control of stripping (Tab. 5, 9). Levels of histamine from the basophils (without and after stripping) incubated with non-coated and specific antibodies coated bacteria were compared. The results were expressed as a percentage of total histamine content in the sample. Histamine release was assayed spectrofluorometrically by using Shore method in Norn modification. The main investigations concerned the basophils from 12 healthy, non-atopic individuals, who had positive immediate skin reactions with at least 1 from 3 microbial strains: Staphylococcus aureus 9615 (unencapsulated), Staphylococcus aureus Smith (encapsulated) and Escherichia coli. Sera containing specific antibodies for these microorganisms were obtained from immunized rabbits. As negative control served sera collected from animals after immunization. Additionally the basophils of 6 asthmatic (intrinsic asthma) patients treated with autovaccines were examined. All patients demonstrated positive late and delayed skin reactions, 3 of them also immediate, to autologous Neisseria and Moraxella species cultured from upper respiratory tract. The bacteria were used as a component of autovaccine and as a basophils stimulating factor in histamine assay. Microbes were incubated with patients own sera before (unspecific serum) and after treatment (source of "specific" antibodies). CONCLUSIONS: 1. Bacteria induced basophil histamine release through two ways: immunological (IgE-mediated) and non-immunological (sugar-lectin interactions). 2. Non-immunological interactions played the main role in basophil histamine release induced by bacteria--both in normal individuals and asthmatic patients. 3. Sera of immunized with bacteria animals partially reduced basophil histamine release induced by homologous strains (Tab. 7). 4. An incubation of autologous bacterial strains with asthmatic patients's sera collected after autovaccines treatment has no influence on basophil histamine release induced by these microbes (Tab. 9). 5. There was no correlation between the skin reactivity to bacteria (both in healthy persons and in asthmatic patients) and the intensity of basophil histamine release induced by microbes.

Adult↗