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Biomedical subjects

A Weyer

Publications and source records attributed to A Weyer.

At least 37 records · Page 2Linked to original sources
PubMed1993

Expression of the alpha chain of human Fc epsilon RI in transfected rat basophilic leukemia cells: functional activation after sensitization with human mite-specific IgE.

The actual dilemma in studying the binding and triggering capacity of IgE from allergic patients is the lack of cultured basophils or mast cell analogs of human origin. Human IgE binds with exquisite species specificity to the high affinity IgE receptor (Fc epsilon RI) expressed on the surface of these cells. In rodents this receptor has been characterized as a tetrameric plasma membrane protein composed of an IgE-binding alpha chain, a beta chain and two disulfide-linked gamma chains. In order to establish a cell line expressing the alpha chain of human Fc epsilon RI which can be triggered with IgE from human patients and specific allergen, we transfected the cDNA coding for the human alpha subunit into rat basophilic leukemia cells. The resulting transfectants express the human alpha chain on the cell surface in the form of a hybrid complex associated with endogenous rat gamma chains. After sensitization with human IgE from mite-specific patients, the transfectant produces a calcium response upon incubation with allergen. The established cell line can be used as a model system to study the mechanism of mast cell triggering through IgE from allergic patients.

Allergens↗
PubMed1992

Identification of allergenic epitopes on Der f I, a major allergen of Dermatophagoides farinae, using monoclonal antibodies.

The antigenic and allergenic structure of Der f I, a major allergen of the house dust mite Dermatophagoides farinae (Df) was investigated by means of a panel of 11 selected monoclonal antibodies (mAb) obtained from BALB/c mice immunized with purified Der f I. The species specificity of these mAb, tested with Der f I and Der p I--the homologous allergen from Dermatophagoides pteronyssinus--was generally restricted to Der f I since 10 out of 11 mAb reacted only with this allergen. Epitope specificity of the mAb was determined by both competitive inhibition and sandwich ELISA experiments. The results indicated the presence of at least four non-overlapping, non-repeated antigenic sites on Der f I, which were recognized by one or several mAb (sites A, B, C and D). Comparative epitope specificity studies between human IgE antibodies and mice mAb were performed, on sera and basophils of Df sensitive patients, using different inhibition assays (ELISA and histamine release experiments). The degree of inhibition varied between the patients and upon the assay design. Most of the mAb tested were found to significantly inhibit the binding of human IgE to Der f I (p less than 0.01) when compared with Der p I specific mAb as a control. The mAb reacting with site A was found to be the most potent inhibitor, presenting a mean inhibition of up to 56% in ELISA as well as in histamine release experiments. The results show that both human IgE antibodies and mAb can be directed against identical or closely related epitopes of Der f I. Therefore anti-Der f I mAb constitute immunologic probes in further allergenic epitope and peptide analysis of this major mite allergen.

Allergens↗
PubMed1990

Seasonal increase of spontaneous histamine release in washed leucocytes from rhinitis patients sensitive to grass pollen.

The spontaneous histamine release (SHR) in basophils from patients sensitive to grass pollen has been studied before and during the 1987 grass pollen season. Nineteen patients were recruited on seasonal rhinitis symptoms, positivity for cutaneous tests and for serum-specific IgE with grass pollen. At the time of the biological investigations the patients were following a clinical trial of hyposensitization, including placebo, calcium phosphate and aluminium hydroxide-adsorbed grass pollen extract treatments. During the pollen season, grass pollen counts and clinical scores were checked over a 40-day period. Mean SHR was significantly higher during the pollen period than before, for the whole population of 19 patients (10.9% and 4.6%; P less than 0.005) as well as when the high SHR responders were excluded (5.5% and 3.6%; P less than 0.01). No significant correlation existed between SHR and clinical scores or treatments. SHR could be inhibited at 4 degrees C, in absence of CA++ or of oxidative metabolism and thus originated from cells actively secreting histamine.

Adolescent↗
PubMed1990

[Indication for and results of the application of glycerol-preserved homologous split-thickness skin following burns].

Since 1983 the treatment of second-degree burns with glycerol-conserved allogenic split-thickness skin grafts is published. In case of actual problems with AIDS the gathering of split-thickness skin was modified and a new method for gaining split-thickness skin of organ-donors created to prevent the virus transfer. Because of these high security in contagiousness the skin graft transplantation with allogenic glycerol-conserved donor-skin in case of second-degree-burns was standardized in the Berlin Burn Center. To prevent the formation of granulation tissue after second-degree burns a tangential debridement of necrotic corium will be done in 1/10 mm thick slices on the third posttraumatic day and the defects covered with 1:1.5 mesh grafts extended. The results of 267 patients in 1988 and 1989, who were treated in accordance to this regimen, will be demonstrated. In 11% of cases the alloplastic skin graft in adults was not rejected 6 month after transplantation and in 2% of cases the depth of burn was not estimated properly and hypertrophic scars had to be excised and covered with autogenous split-thickness skin. General second-degree-burn healed after debridement and covering with allogeneic split-thickness skin without formation of hypertrophic scars.

Adult↗
PubMed1989

Enhancement of the histamine releasing activity of mouse monoclonal anti-human IgE antibody xb6-16 when present in aggregated or complexed forms.

FPLC purification of mouse monoclonal anti-human IgE antibody xb6-16 showed 2 major peaks of different molecular weight, peak 1 (greater than 10(6) d) and peak 3 (1.6 x 10(5) d). Peak 1 consisted of IgG1 and IgM, peak 3 of IgG1 only. On a protein weight basis, peak 1 was 100 times more potent than peak 3 in inducing histamine release from human basophils. Preincubation of peak 3 with anti-IgG1 enhanced the mediator release triggered by this fraction. On this basis, the potentiating effect of aggregated IgG1 or IgG1-IgM complexes on mediator release from basophils is discussed.

Animals↗
PubMed1987

Monoclonal anti-human IgE: histamine release capacity and effect on in vitro sensitization of human basophils.

IgE-anti-IgE complexes were formed by preincubation of a human myeloma IgE with a monoclonal anti-human IgE antibody at different concentrations. Binding of IgE onto the anti-IgE inhibited the histamine release capacity of anti-IgE from basophils. The IgE cell-binding capacity was altered by the IgE/anti-IgE ratio in the preincubation buffer. Heating of the complexes gave a partial recovery of the anti-IgE degranulation capacity, suggesting that the monoclonal anti-IgE is specific for an epitope present on the D epsilon 2 domain.

Antibodies, Anti-Idiotypic↗
PubMed1987

Basophil sensitivity and reactivity to monoclonal anti-human IgE after in vitro sensitization with human myeloma IgE.

Leucocytes from human peripheral blood were acid eluted and sensitized in vitro with increasing concentrations of radiolabelled myeloma IgE. This sensitization step was performed with or without 30% IgE depleted serum. After the IgE binding, cells were washed and submitted to a challenge with monoclonal anti-IgE for the determination of the cellular sensitivity and reactivity in a histamine release assay. A sample of each of the sensitized cells was analyzed for its radioactivity and the number of basophils quantified, thus allowing the determination of the mean number of IgE molecules per basophil. Raising the IgE concentrations in the sensitization procedure led to an increase of the IgE on the basophil membrane, and to a concomitant elevation of the cell sensitivity. The presence of serum during the binding of IgE onto the cells lowers slightly the binding of IgE to the basophils but decreases strongly the cellular reactivity.

Antibodies, Anti-Idiotypic↗
PubMed1986

Passive in vitro sensitization of human basophils with Dermatophagoides farinae specific IgE.

Basophils from allergic or non-atopic donors were depleted for their native membrane IgE by acid treatment and then passively sensitized by Dermatophagoides farinae specific IgE containing sera. Histamine release experiments were performed with a highly purified allergen (Df 11) on native cells, acid treated cells and passively sensitized cells. In the sensitization procedure, the quantity of the basophil-bound serum IgE is dependent on the concentration of the sensitizing serum IgE and the histamine release capacity is specifically acquired. It is shown that after passive sensitization basophil membrane IgE density as well as basophil sensitivity to Df 11 in histamine release experiments depend on the ratio [Df 11 specific IgE/total IgE] in the sensitizing serum.

Allergens↗
PubMed1986

Prevention of puerperal lactation with Parlodel long-acting (Parlodel LA).

Thirty women who did not want to breast-feed postpartum were treated with Parlodel LA. Immediately after birth 50 mg Parlodel LA were injected i.m. by means of a double-chamber syringe. The aim was to investigate in an open study the clinical efficacy and tolerability of Parlodel LA in the prevention of postpartum lactation. The overall efficacy was very good in 29 women (96.6%) and good in 1 woman (3.4%). In 27 women no symptoms of tenderness, engorgement or milk secretion were found (90%). In two cases slight and moderate mammary pain were reported during a few days, engorgement in only one case during one day and in three cases a slight milk let-down was seen for 1-2 days. In all cases the breast symptoms ceased spontaneously and no rebound lactation occurred in any of the women treated with Parlodel LA. The general tolerability was very good in 29 cases (96.6%) and good in one case (3.4%). No adverse effects were reported in any case. No obvious changes in blood pressure were noticed after the injection. In general a slight decrease occurred in systolic and/or diastolic blood pressure post-partum well within the range of non-treated healthy postpartum women. There were also no signs of orthostatic hypotension or changes in pulse rate accompanying the slight decrease in blood pressure. The local tolerability at the injection site was very good in 23 women (76.6%). Seven had short-lasting pain, slight in 6 cases and moderate in 1. Slight redness was reported in one case.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Thermoinactivation of human IgE: antigenic and functional modifications.

The thermoinactivation kinetics of IgE were studied in experimental models revealing the antigenic properties and the basophil-sensitizing capacity of these immunoglobulins. A pool of human sera containing anti-Dactylis glomerata (Dg) IgE was heated from 5 min up to 4 hr at 56 degrees. The IgE antigenicity was tested by two polyclonal 125I-labelled anti-IgE antibodies; one anti-IgE was specific of the whole Fc epsilon region, while the other had a specificity restricted to the D epsilon 2 domain. Radioimmunoassays showed that the D epsilon 2 epitopes were more rapidly altered than the D epsilon 1 epitopes. The capacity of IgE to bind to basophil Fc epsilon receptors was assayed by passive sensitization experiments. Basophil sensitivity towards the Dg pollen extract was tested by histamine release experiments in the presence of this allergen. A progressive decrease in cell sensitivity was observed when IgE samples used for cell sensitization were heated for longer than 5 min. Thermoinactivation kinetics of IgE revealed an unexpected increase in the apparent quantity and biological activity of IgE heated for 5 min at 56 degrees. This fact could be due to auto-anti-IgE antibodies linked to the unheated IgE and which interfere with the biological activities of IgE and their quantification.

Basophils↗
PubMed1985

Relationship between specific circulating IgE, basophil cell-bound IgE and histamine release induced by purified allergens of Dermatophagoides farinae.

In this study we analysed the presence and proportions of IgE specific for Df 6 and Df 11, two purified allergens of Dermatophagoides farinae. The characterisation of serum IgE and cell-bound IgE for 3 D. farinae-sensitive patients were performed by CRIE, RAST and PRIST assays. Furthermore the basophils from these same patients were studied by histamine release assays in the presence of Df 6 and Df 11. All the individual patient's cell and serum IgE samples displayed the presence of IgE antibodies specific for Df 6 and Df 11, but the relative quantities of the IgE for these two specificities were characteristic of each patient. The ratios (Specific IgE for Df 11) : (Specific IgE for Df 6) (ratio 11 : 6) were similar in the serum and on the cells for an individual patient. As judged by histamine release assays, the basophil sensitivities towards Df 6 and Df 11 were very different from one atopic patient to another. Moreover cell sensitivities reflected the proportion of Df 6- and Df 11-specific IgE antibodies found in the serum and in the cell eluate.

Animals↗
PubMed1985

Histamine and mast cell distribution in the gastrointestinal wall of the rat: comparison between germ-free and conventional rats.

The distributions of histamine and mast cells in the intestinal mucosa have been studied in conventional (CV) and germ-free (GF) rats. Both distributions do not appear to be uniform throughout the gastrointestinal tract. The presence of digestive microflora influences these distributions: more histamine and mucosal mast cells are present in the small intestine of CV than in GF rats. Paradoxically the opposite is observed in the large intestine. Differences in mast cell counts in the crypt area of the small intestine (higher in CV than in GF rats) confirm the role of microflora on crypt cell proliferation due to a mild chronic inflammation. In the large intestine, however, the microflora appears to have a more complex influence and could act indirectly on histamine turnover.

Animals↗
PubMed1981

Grass pollen hyposensitization versus placebo therapy. I. Clinical effectiveness and methodological aspects of a pre-seasonal course of desensitization with a four-grass pollen extract.

The present work reports the results of a double-blind clinical trial, comparing the effects of hyposensitization treatment versus placebo in 33 patients with allergic rhinitis, sensitive to a crude extract of the pollen of four different grasses (Dactylis glomerata, Lolium perenne, Secale cereale, and Phleum pratense). The distribution of these patients in the two groups was done randomly and gave two comparable groups, as far as clinical and biological features are concerned. The treatment course included five low doses of the aqueous extract followed by 12 injections of Al(OH)3-adsorbed aliquots of the same extract. Evaluation of the clinical scores was based on diary cards on which symptoms and medications were recorded. A reevaluation of the significance of the symptom and medication scores is presented and the link between both scores is studied. Particular attention is given to the methodological and statistical problems raised during this study. The non-parametric tests reveal a significant difference (P less or equal to than 0.03) in the total clinical score between the treated and the placebo groups for the second half of the observation period, when the pathology was most intense.

Adolescent↗
PubMed1980

Studies on Dermatophagoides pteronyssinus allergens: measurement of the relative potencies of D. pteronyssinus purified extracts by in vitro and in vivo methods.

To standardize the Dermatophagoides pteronyssinus extracts used in clinical allergy practice, the relative potencies of several purified extracts were estimated by radioallergosorbent test (RAST) inhibition, histamine release, and intracutaneous titration testing, and the results were compared. The potencies of nine independently prepared D. pteronyssinus extracts were assayed with respect to an extract adopted as a reference. In vivo the cutaneous wheal surface after intradermal injections was measured on a population of D. pteronyssinus-sensitive subjects. In vitro RAST inhibition was performed with the reference extract as allergosorbent and with a pool of human IgE-rich sera from patients sensitized to D. pteronyssinus but untreated. For histamine release human basophils from patients allergic to D. pteronyssinus were used. In the three method dose-response curves were plotted for the reference extract and the other extracts. A comparison of the measurement of in vitro and in vivo potencies is reported. Simialr results were obtained with the three methods: all the extracts but one were as potent as the reference preparation. However, for routine purposes RAST inhibition appears to be the most convenient and reliable procedure.

Allergens↗
PubMed1978

Cellular histamine release, specific and total serum IgE levels in hay fever patients and controls.

The amount of histamine released from blood leucocytes by allergen, the amount of allergen required to release 50% histamine and the total IgE and IgE specific for Dactylis glomerata are compared in nine hay fever patients and five control individuals. The variation with time of total IgE, of specific IgEe and of the percentage of histamine released at a fixed allergen concentration, corresponding to the cellular sensitivity, is shown for one control individual with positive in vitro and skin tests, but without clinical symptoms. For four patients with a low total IgE level the evolution of these parameters during a 1 year treatment period is presented.

Adult↗
PubMed1976

[Intracellular histamine content in human basophils and individual variation in allergic persons during densensitization].

A positive correlation has been found to exist between the percentage of basophiles and the histamine content in a suspension of washed human leukocytes obtained from allergic and healthy donors. The mean value of histamine per basophile was 1,9 +/- 0,3 pg. The leukocyte histamine content was measured as a function of time in a non-allergic person and during the desensitization period of allergic patients.

Basophils↗