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A L de Weck

Publications and source records attributed to A L de Weck.

At least 19 recordsLinked to original sources
PubMed1992

Anti-IgE autoantibodies mistaken for specific IgG.

During isolation of specific IgE by affinity chromatography, we obtained IgG acting as "specific IgG" in dot immunoassay and RAST. Further analysis of this fraction revealed that this specific IgG was indeed an immune complex consisting of IgG anti-IgE autoantibodies and specific IgE that falsely appeared as specific IgG in the immunoassays. After disruption of complexes, more IgE became accessible, resulting in increased counts per minute in the RAST. Thus, anti-IgE autoantibodies may hinder determination of specific IgE in in vitro immunoassays, since they hide specific IgE immunologically. To demonstrate the isotope specificity of such immune complex-derived IgG, the purified anti-IgE autoantibodies were radiolabeled and used as detection antibodies in immunoblotting. These autoantibodies recognized different IgE preparations, including a recombinant IgE peptide.

Adult↗
PubMed1992

B lymphoblasts show oxidase activity in response to cross-linking of surface IgM and HLA-DR.

Human B lymphocytes express components of the superoxide generating system of phagocytes, NADPH oxidase. We studied regulation of this 'B-cell oxidase' during in vitro blast transformation, using Lucigenin-amplified chemiluminescence (CL) to detect superoxide release. While freshly isolated tonsil B lymphocytes showed no CL responses, culture with phorbol myristate acetate (PMA) and ionomycin induced susceptibility to CL triggering by anti-IgM and anti-HLA-DR. Maximal effects were observed after 3 days of culture with 0.4 ng/ml PMA + 1 microgram/ml ionomycin. Cells from such B lymphoblast cultures showed no CL responses to opsonized zymosan. In contrast, peripheral blood mononuclear cells, where monocytes are the predominant oxidant source, showed CL responses to opsonized zymosan but not to anti-IgM and anti-HLA-DR, either before or after culture with PMA + ionomycin. Culture of B cells with the surface immunoglobulin cross-linking agent staphylococcus aureus Cowan I also led to emergence of a CL, response to anti-IgM, which was enhanced by interferon-gamma. Interestingly, markedly fewer B blasts than freshly isolated B lymphocytes expressed cytochrome b-558 surface antigen. Thus, the B-cell oxidase is up-regulated during blast transformation and can be triggered via surface IgM and HLA-DR; however, this appears to be restricted to a subset of B lymphoblasts.

B-Lymphocytes↗
PubMed1992

Peptide analogues of consensus receptor sequence inhibit the action of cytokines on human basophils.

A novel cytokine receptor family has been defined based on structural homologies between the extracellular receptor domains. All receptors share a WSXWS consensus sequence just outside the plasma membrane. To evaluate whether this box of homology has a role in receptor function we synthesized peptides encompassed within the WSXWS region. In a basophil mediator release assay, three peptides inhibited the priming effect of interleukin (IL)-3, IL-5, and granulocyte/macrophage colony-stimulating factor (GM-CSF) on synthesis of leukotriene C4 induced by chemotactic peptides. The study suggests that, analogous to the RGD motif in adhesive proteins, the WSXWS motif serves as a recognition site for functional protein-protein interaction of cytokine receptors.

Amino Acid Sequence↗
PubMed1991

Interleukin 8-inhibitor and inducer of histamine and leukotriene release in human basophils.

We have shown previously that interleukin 8 (IL-8) induces histamine and leukotriene release in human basophils exposed to interleukin 3 (IL-3). We now found that pretreatment with low concentrations of IL-8 selectively inhibits this response. Inhibition was significant at 0.01 nM IL-8 and virtually complete at 1 nM, which is about 100-fold lower than the concentration required for induction of mediator release. IL-8 dependent responses were also inhibited, albeit to a lesser extent, by preincubation with neutrophil-activating peptide 2 (NAP-2), but not with connective tissue-activating peptide III (CTAP-III) or platelet factor 4 (PF4). Release induced by C5a, fMet-Leu-Phe, or anti-IgE antibody, by contrast, was not affected.

Basophils↗
PubMed1991

Platelet-activating factor induces mediator release by human basophils primed with IL-3, granulocyte-macrophage colony-stimulating factor, or IL-5.

The phospholipid platelet-activating factor (PAF) is a potent cell-derived bioactive molecule thought to be involved in diverse inflammatory processes. It has been shown that PAF can activate different leukocyte types and platelets, particularly in synergy with other agonists. In this study we examined the effect of PAF upon the release of histamine and leukotriene (LT) C4 by basophils when added alone and in combination with different agonists and cytokines. PAF by itself did neither induce histamine release nor the generation of LTC4 by basophils. However, basophils primed by the hematopoietic growth factors (hGF) IL-3, granulocyte-macrophage (GM)-CSF, or IL-5 (10 ng/ml) released preformed and de novo synthesized mediators in response to PAF at 10 to 100 nM concentrations. The extent of mediator release by hGF primed basophils in response to PAF was similar to that induced by an optimal concentration of monoclonal anti-IgE. Thus, similar to NAP-1/IL-8 and C3a, PAF efficiently stimulates mediator release in hGF-primed basophils only. However, PAF was clearly a more potent trigger of LTC4 formation in IL-3-primed cells than NAP-1/IL-8 or C3a. When PAF was used as a second trigger, the priming effect of IL-5 was less than that of IL-3 or GM-CSF, whereas the response for other IgE-independent agonists (i.e., C5a or FMLP) was augmented equally by all three hGF. IL-1 beta-pretreated basophils released minimal amounts of histamine in response to PAF. Neither TNF-alpha nor PAF, nor the combination thereof, was able to induce basophil mediator release. The efficiency of the different cytokines to prime for PAF responsiveness was strikingly similar to their capacity to enhance anti-IgE-induced mediator release. Similar to other IgE-independent agonists, the kinetic of mediator release in response to PAF was very rapid. PAF pretreatment of basophils did not enhance mediator release in response to diverse agonists, such as C5a and FMLP, in contrast to the capacity of PAF to augment the response of other leukocyte types to appropriate stimuli. Thus, depending on the presence of IL-3, GM-CSF, or IL-5, PAF is a potent basophil agonist capable of inducing histamine release as well as de novo synthesis of LTC4.

Basophils↗
PubMed1991

Receptor-operated activation of polymorphonuclear leukocytes: different effects of NAP-1/IL-8 and fMet-Leu-Phe or C5a.

We examined the production of PAF and LTB4 by PMN in response to NAP1/IL-8 alone, or after preincubation with GM-CSF, which has been shown to enhance PMN responsiveness and to prime PMN for production of those bioactive lipids. NAP-1/IL-8 does not induce the synthesis of PAF and LTB4 from endogenous phospholipid precursors, even after preincubation with GM-CSF. In addition and again in contrast to fMLP and C5a, NAP-1/IL-8 fails to induce an enhanced oxidative burst in GM-CSF primed PMN. Exogenously added PAF or LTB4 can mimic the priming effect of GM-CSF for an enhanced oxidative burst in response to all examined chemotactic peptides including NAP1/IL-8. Our data reveal a possible autocrine role of PAF and LTB4 in the enhanced responsiveness of GM-CSF primed PMN towards fMLP or C5a, but not NAP-1/IL-8.

Arachidonate 5-Lipoxygenase↗
PubMed1991

[Relationship between T-subsets and clinical aspects of HIV-associated diseases].

HIV predominantly infects the CD4+ T cells, which during the progression of the disease are eliminated, causing an immune deficiency which renders the patients more susceptible to infections. To evaluate the relevance of the CD4+ T cell elimination and thus the clinical usefulness of CD4/CD8 subset determinations in HIV infected persons, we investigated whether analyses of 667 subset determinations of 365 patients correlated with clinical stages of HIV-infection (CDC classification). Progress of HIV related disease was accompanied by a fall in CD4+ cells and an increase in CD8+ cells, leading to a drastically reduced CD4/CD8 ratio. This change of T-cell subset values correlated well with the clinical classification (CDC). It was, however, only statistically significant if percent values were used, but not if absolute CD4 cell counts, calculated from the peripheral lymphocyte count, were considered. While patients in CDC stage IVC2 (mainly Candida stomatitis) did not differ from stages IIB, IIIB, IVA, we found statistically lower CD4 values if the patients had stage IVA plus IVC2. Stage IVC1 (mainly Pneumocystis carinii pneumonia [PcP, n = 20]) had even lower CD4 values, as PcP appeared almost exclusively in patients with CD4 counts below 20% or 200/microliter. The lowest CD4 counts were observed in patients with Kaposi sarcoma (n = 11) with CD4 cells less than 10% and significant elevated values of CD8 cells (greater than 50%). While the total lymphocyte count correlated with the absolute counts of CD4 and CD8 cells, it was impossible to estimate the T-subset distribution from the absolute lymphocyte count. Our investigations show that a decreased number of circulating CD4 cells correlates well with an increased tendency to develop infections, and thus support the relevance of CD4 cell measurements for the optimal care of asymptomatic HIV infected persons in particular. They also show that the percent values correlate better with clinical stage than the absolute CD4 cell count.

CD4-Positive T-Lymphocytes↗
PubMed1991

Selective stimulation of CD4+ versus CD8+ T-cell subsets in symptomatic and asymptomatic HIV-1-infected individuals.

To analyze the proliferative capacity of CD4+ or CD8+ T-cell subsets of individuals infected with human immunodeficiency virus type 1 (HIV-1) and to optimize the in vitro conditions for virus replication, CD4+ or CD8+ cells of HIV-1-infected patients were selectively activated inside the whole peripheral blood mononuclear cell (PMNC) population by dual antibody stimulation. To do so PMNC of HIV-1-infected individuals were stimulated with the per se nonmitogenic anti-CD3 antibody fragment BMA030 F(ab)2 crosslinked through goat antimouse antibodies with an anti-CD4 or an anti-CD8 antibody, which lead to selective proliferation of either the CD4+ or the CD8+ T-cell subset. In the presence of monocyte supernatant and recombinant interleukin-2 (rIL2) CD4+ cells of HIV-1 patients responded normally upon such stimulation as their proliferation correlated (r = 0.9) to the percentage CD4+ cells present in the PMNC population. Selective stimulation and proliferation of CD8+ cells could, however, only partially be elicited by dual antibody stimulation, even in the presence of rIL-2 and monocyte supernatant. Their proliferative response did not correspond (r = 0.1) to the percentage CD8+ cells present in the PMNC culture. A positive correlation (r = 0.7) was detected only between percentage CD8+ HLA-DR- cells and proliferation. This confirmed previous studies showing that the defective in vitro proliferative response of peripheral blood lymphocytes of HIV-infected individuals to mitogens, which is usually interpreted being due to a CD4 cell defect, is actually due to a failure of CD8+DR+ cells to proliferate.(ABSTRACT TRUNCATED AT 250 WORDS)

Antilymphocyte Serum↗
PubMed1991

IgG anti-IgE autoantibodies in immunoregulation.

Human sera contain anti-IgE autoantibodies with diverse biological functions in vitro. Opposite functions can be shown for triggering of IgE-mediated histamine release from human basophils in terms of anaphylactogenic or nonanaphylactogenic autoantibodies. Furthermore, autoantibodies are either capable of removing IgE from the surface of CD23-positive cells of binding more IgE to such cells. A similar dichotomy seems also to exist for the effect of autoantibodies on human IgE mRNA synthesis as well as IL-4-induced proliferation of human mononuclear cells. Thus, anti-IgE autoantibodies may represent a key factor in the manifestation and the development of allergic disease.

Antibodies, Anti-Idiotypic↗
PubMed1991

Are allergen-specific IgG mainly IgG anti-IgE autoantibodies?

A large proportion of specific IgE occurred in immune complexes with anti-IgE autoantibodies in sera from nonhyposensitized allergic patients. These autoantibodies were misinterpreted as 'specific IgG' in different immunoassays such as dot immunoassays and the radioallergosorbent test (RAST), leading to overestimation of specific IgG. Purified immune complexes contained even more IgG than IgE antibodies. Heating of the complexes liberated specific IgE, producing an upwards RAST class shift. Thus anti-IgE autoantibodies are hiding the specific IgE, which is thereby underestimated. It is not known whether the hiding anti-IgE autoantibodies are also effectively neutralizing circulating or cell-bound IgE and might represent the actual blocking antibody.

Allergens↗
PubMed1991

Regulation of mediator release by human basophils: importance of the sequence and time of addition in the combined action of different agonists.

Biologically active molecules affecting basophil function can be divided into 4 groups according to their capacity to induce basophil degranulation and/or leukotriene generation: (1) full agonists such as anti-IgE or fMLP, which induce both histamine and leukotriene release; (2) partial agonists such as C5a, which induces degranulation only; (3) incomplete agonists such as neutrophil-activating peptide-1, platelet-activating factor or C3a, which induce mediator release only after cytokine preincubation, and (4) basophil response modifiers, such as interleukin-3, interleukin-5 and granulocyte/macrophage- colony-stimulating factor, which (a) enhance the releasability to all basophil agonists, (b) change the mediator profile, (c) enhance the rate of mediator release, (d) render basophils responsive to lower agonist concentrations and (e) render basophils responsive to incomplete agonists. We demonstrated that histamine release and de novo synthesis of lipid mediators are clearly separately regulated, and that combined actions of different molecules are of importance. In particular, the type(s), the time interval and the sequence of action of basophil-activating molecules are crucial for the final outcome of the basophil release reaction.

Basophils↗
PubMed1991

Incorporation of biotinylated nucleotides for the quantification of PCR-amplified HIV-1 DNA by chemiluminescence.

Chemiluminescent detection of polymerase chain reaction (PCR-)amplified DNA was used as a quantitative method for detecting HIV-1. For this purpose, biotinylated dUMP was directly incorporated into the amplified DNA during the PCR reaction. Biotinylation was visualized in an enzymatic reaction using avidine-conjugated alkaline phosphatase and its chemiluminescent 1,2-dioxetane substrate AMPPD, which decomposes upon dephosphorylation and emits light. Light emission was either detected with X-ray films or quantified with a single-photon counting camera connected to a computer imaging system. The specificity of the method was shown by hybridization with a biotinylated or radiolabelled HIV-1-specific oligonucleotide probe. Besides being quantitative, this method represented a non-hazardous, rapid and sensitive technique for the detection of HIV-1 DNA.

Biotin↗
PubMed1990

Interleukin 3 and granulocyte/macrophage-colony-stimulating factor render human basophils responsive to low concentrations of complement component C3a.

Complement component C3a is an anaphylatoxin known to induce plasma exudation and smooth muscle contraction in tissues. The effects on inflammatory effector leukocytes, however, are poorly defined and controversial, being at best weak and occurring at very high C3a concentrations. Here, we examined the effect of C3a upon mediator release from human basophils, with and without pretreatment with interleukin 3 (IL-3), a hematopoietic growth factor recently found to profoundly modify the basophil response to various cell agonists. In the absence of cytokines, C3a, even at a concentration of 1 microM, was ineffective or only weakly stimulatory for basophil mediator release. However, when basophils were pretreated with IL-3 at concentrations of only 0.01-1 unit/ml, they became responsive to C3a, releasing large amounts of histamine and also generating leukotrienes. Surprisingly, almost optimal effects occurred with even very low C3a concentrations (1 nM). Another hematopoietic growth factor, granulocyte/macrophage-colony-stimulating factor (GM-CSF), was also found to render basophils capable of responding to C3a, but the effect was weaker than that of IL-3. C3a-induced histamine release and leukotriene generation occurred rapidly in IL-3-primed cells, being complete after 0.5 and 2 min, respectively. The rapid and strong degranulation response, occurring at very low concentrations of C3a, suggests the presence of a high-affinity C3a receptor on basophils, which might be inducible by cytokines. Our results demonstrate that, depending on the presence of IL-3 or GM-CSF, C3a is a potent basophil activator, and such a phenomenon could be of relevance in various inflammatory processes, especially hypersensitivity reactions.

Basophils↗
PubMed1979

Suppression of phosphorylcholine-specific IgE antibody formation in BALB/c mice by isologous anti-T 15 antiserum.

In order to study the regulation of IgE antibody formation, isologous anti-idiotypic antisera against the phosphoryl choline (PC)-specific BALB/c myeloma proteins T 15 and M 167 were passively administered to BALB/c in the course of an anti-PC IgE response. Isologous anti-T 15 antiserum had a long-lasting suppressive effect on the formation of IgE antibodies with PC specificity, whereas administration of anti-M 167 antiserum had no or only little effect, similar to that of normal BALB/c serum. This indicates that anti-PC IgE antibodies consist mainly of the T 15 idiotype or of cross-reacting idiotypes, and that IgE response is accessible to regulation with anti-idiotypic antibodies. This murine model may permit the study of regulation of an IgE response largely restricted to few defined idiotypes characterized as tumor proteins.

Animals↗