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Biomedical subjects

L Berrens

Publications and source records attributed to L Berrens.

At least 19 recordsLinked to original sources
PubMed1997

Haemolytic complement consumption by Parietaria pollen extracts in relation to peptide-bound flavonoids.

Inhaled allergens from house dust, mites or animal danders activate human complement in vitro by engaging the C1-component through a non-antibody-dependent mechanism. These earlier findings are extended by showing that the allergenic components in extracts of Parietaria pollen are almost equally potent complement activators as those from house dust or mites. Spectroscopic evidence indicates that haemolytic complement consumption by the Parietaria allergens and their enzymic fragments is most likely related to post-translational side-chains comprising flavonoid derivatives. These adsorbed and/or peptide-bound tannin-like structures may also explain the exceptional stability of the high- and low-molecular mass allergenic components in Parietaria pollen extracts.

Complement Activation↗
PubMed1997

Complement activating agents in allergenic extracts.

OBJECTIVE: Extracts of environmental allergens, moulds and plant pollens are known to consume haemolytic complement (huC) in human serum in vitro through the antibody-independent engagement of the first component C1 of the classical pathway. The present work was undertaken to establish the nature and characteristics of the complement activating agents in allergenic extracts and to probe their relationship with the IgE-binding allergens. MATERIALS AND METHODS: A large series of different > 10 kDa allergenic products was investigated for their capacity to consume haemolytic complement in the sera of allergic patients with specific anti-allergen IgE antibodies, as well as in normal control sera. UV-spectroscopy was used for categorizing the non-protein components in the extracts. RESULTS: The experiments confirmed that huC is consumed in an antibody-independent fashion and in a qualitatively similar, but quantitatively distinct manner. The ratio of the complement activating potencies among the different allergenic preparations thereby remained constant and independent of the serum source, while an overt relationship with specific IgE-antibodies could not be established. UV-spectroscopy of the allergenic preparations revealed the presence of chemical decomposition products in nearly every extract and roughly in proportion to the complement activating potencies. CONCLUSION: The data support the idea that huC-activation by traditional allergenic extracts is mainly due to by-stander degradation products of the melanoidin (Maillard) or tannin type, which may or may not occur in physical association with the IgE-binding protein allergens.

Allergens↗
PubMed1997

Complement inactivation by allergenic plant pollen extracts.

Dialyzed aqueous extracts of plant pollen are widely used in the clinical practice of allergy for diagnostic and therapeutic purposes. The present investigation shows that such allergenic extracts are capable of consuming complement in every human serum, independent of the clinical condition. Complement is engaged by way of the first component C1, but without the participation of allergen-specific antibodies. The capacity of distinct pollen extracts to inactivate haemolytic complement was found to depend on the plant species, the most potent extracts being from the pollen of the weeds and trees. Analysis by UV-spectroscopy of the flavonoids remaining firmly bound to the proteins gives rise to the proposal that complement inactivation by allergenic and non-allergenic pollen extracts is due to polyphenolic (flavonoid) structures complexed with, or chemically conjugated to, the pollen proteins.

Allergens↗
PubMed1997

Comparative study of the complement-activating and specific IgE-binding properties of ragweed pollen allergen.

Previous reports have defined the capacity of ragweed pollen extract (RWA) to activate human complement (C) in fluid phase through the classical pathway and have ascertained a strong correlation between the extent of complement activation and the severity of symptoms of allergic rhinoconjunctivitis during the ragweed blooming season. In the present study the complement-activating and specific IgE-binding capacities of various ragweed allergen preparations were compared. Elimination of physically adsorbed (flavonoid) pigments from the allergenic proteins had no significant effect on their complement-consuming capacity, although the process strongly diminished specific IgE binding. Removal of an IgE-binding trypsin inhibitor from RWA significantly enhanced RWA-induced complement activation, whereas it did not change IgE binding. These findings indicate that neither the physically adsorbed pigments nor the trypsin inhibitor are involved in complement activation by ragweed pollen allergens, and suggest that complement activation and specific IgE binding are distinct molecular properties of ragweed pollen allergen.

Allergens↗
PubMed1996

Monoclonal antibodies against Dermatophagoides group I allergens as pseudo-cystatins blocking the catalytic site of cysteine proteinases.

The enzyme allergens Der p I and Der f I produced by the house dust mites Dermatophagoides pteronyssinus and D. farinae display partial sequence homology with other members of the cysteine proteinase superfamily. We report that certain widely used mouse mAbs against these Group I allergens indeed crossreact with the plant enzymes papain, bromelain and ficin. The recognition sites of these anti Group I mAbs comprise conformational and thermolabile epitopes involved in molding the catalytic center of the proteinases. Thus, the mAbs inhibit the enzymatic hydrolysis of specific chromogenic substrates by the Group I allergens, while specific cysteine proteinase inhibitors abolish the recognition of the enzymes by the mAbs. Similarly, activation of the thiol-proteases with L-cysteine abrogates their binding in the two-site mAb system, indicating that the mAbs recognize a proenzyme conformational peptide epitope. It follows that mAb-based assays for mite Group I components can neither detect the allergens after inactivation, nor in their fully activated forms.

Animals↗
PubMed1996

Extraordinary stability of IgE-binding Parietaria pollen allergens in relation to chemically bound flavonoids.

It is known that the skin-active and IgE-binding components in Parietaria pollen extracts are not restricted to the predominant protein allergens of M(r) 12000-15000, but are present as well among the naturally occurring constituents of M(r) < 10000. Indeed, the IgE-binding Parietaria pollen components are quite heterogeneous, ranging from high- to low-molecular mass, whereby the IgE-binding epitopes display an unusual chemical stability. Furthermore, the pollen of Parietaria species demonstrably contain a high proportion of flavonoid pigments. Since these pollen grains cannot be collected entirely free from non-pollen plant parts, the usual allergenic extracts of Parietaria encompass both the polyphenolic substrate molecules and the enzyme polyphenoloxidase as ingredients for the oxidative generation of flavonol-protein conjugates during the extraction process. In the present work this is illustrated by spectroscopic analyses of the free and bound flavonoids in Parietaria pollen extracts, as well as of the peptide fragments produced from the allergenic proteins by enzymatic or chemical hydrolysis. None of these relatively harsh treatments had a significant effect on the IgE-binding properties of the allergenic (sub-)components, even though detectable proteins in isoelectric focusing and immunoblotting were lost. It is proposed that the extraordinary stability of IgE-binding Parietaria components over a wide molecular range may be attributed to chromophoric flavonoid side-chains as (parts of) the corresponding B-cell epitopes.

Allergens↗
PubMed1996

Binding affinities of allergens from pollen, mites, and house dust for specific IgG subclass antibodies.

The distribution and affinity of IgG subclasses against various aeroallergens were assessed by inhibition of specific antibody binding. Two parameters from the dose-response curves were taken as indicative of antibody affinity: the point of 50% inhibition and the value of the slopes on double-log plots. It was found that IgG4 antibody specific for aeroallergens (i.e., from pollens of several species of Gramineae, Olea europaea, and Parietaria judaica and from house dust) usually exhibits high affinity, except for Dermatophagoides pteronyssinus. High binding affinity was also displayed by IgG1 subclass antibodies against the allergens of O. europaea and P. judaica. Distinct IgG subclass affinity profiles were observed for the allergens of grass pollen (i.e., Holcus lanatus) and dust mites (i.e., D. pteronyssinus). These results demonstrate that IgG subclass distribution, as well as antibody affinity, depends on the nature of the sensitizing allergen.

Adult↗
PubMed1995

IgE-binding trypsin inhibitors in plant pollen extracts.

In an attempt to access the possible role of protease-antiprotease mechanisms of non-immune defence in pollinosis, only low levels of trypsin-, kallikrein- or plasmin-like proteinases could be detected in aqueous pollen extracts. In contrast, several pollen species displayed appreciable trypsin inhibitory activity, e.g. Parietaria, Olea, Ambrosia, Rumex, Chenopodium, Holcus and Poa spp. These proteins of the serpin family of anti-proteinases were found to bind specific IgE-antibodies from the serum of hay fever patients. As examples, the IgE-binding trypsin inhibitors from the pollen of Parietaria judaica and Ambrosia elatior were purified and characterized as acidic proteins with pI 4.2 and a molecular weight of 20-24 kDa.

Allergens↗
PubMed1995

Do IgE-IgG complexes occur in the circulation?

IgG anti-IgE autoantibodies in human allergic sera have been investigated using an enzyme immunoassay on microplates coated with anti-human IgE MoAb. After incubation with serum, the plates were developed with peroxidase-labelled anti-human IgE MoAb for the determination of total IgE levels, or with anti-IgG MoAb for evaluating IgG anti-IgE autoantibodies. Using this methodology, no correlation was found between total IgE and IgG anti-IgE levels in groups of sera of allergic individuals. Although the results obtained with enzyme-labelled anti-IgG are often interpreted as indicative of IgE-IgG complexes captured from the serum, molecular sieving on gel columns as well as direct ultrafiltration experiments through 300-kD membranes demonstrate that such complexes do not occur preformed in the circulation, but arise de novo on the anti-IgE-coated solid phase during in vitro incubation with human serum. It is suggested that IgG anti-IgE autoantibodies react with IgE only after the latter has undergone a conformational change, either by colloidal manipulation or after reaction with allergen.

Adult↗
PubMed1994

Evaluation of the potency of allergenic extracts by inhibition of IgG-antibody binding.

A method is described for the in vitro potency evaluation of allergenic extracts by using their capacity of binding to specific human IgG antibodies. The results obtained with this inhibition-type enzyme immunoassay are compared with the analyses by the customary method of IgE antibody binding. A large series of allergenic protein fractions from the pollen of the Gramineae, Olea europea, Parietaria judaica, and from the dust mite Dermatophagoides pteronyssinus as well as from cat dander and peanuts were examined for inhibition of specific antibodies of both IgG and IgE isotypes. Potency evaluation by inhibition assays for IgE- and IgG-binding showed a significant correlation for the points of 50% inhibition (r = 0.92, p = 0.0001), but not for the slopes of the inhibition curves, i.e. the respective antibody avidities. Evidence is provided that the strict relationship between IgE- and IgG-inhibition by allergens could not be explained by possible cross-contaminations of the anti IgE- or anti IgG-reagents employed in the immunoassays. It is concluded that the inhibition of IgG-antibody binding presents a fast, reliable and low-cost alternative for the potency control of allergens used in clinical practice.

Allergens↗
PubMed1994

A competitive enzyme immunoassay Subclass for the determination of total IgG-subclass levels in human serum. Comparison with single radial immunodiffusion.

A quantitative immunoassay has been developed for the determination of the total IgG subclass levels in human serum. The method is based on an enzyme immunoassay in which IgG subclass proteins IgGx in an unknown serum sample compete with a known quantity of peroxidase (PO)-labelled IgGx in fluid phase for subclass-specific monoclonal antibodies coated to the solid phase of microtiter wells. Using a series of human blood samples an excellent correlation was observed with the IgG-subclass levels determined by single radial immunodiffusion.

Binding, Competitive↗
PubMed1993

[Storm during the dog days; observations with an article by Dr. W. Storm van Leeuwen from 1932].

In 1932 Storm van Leeuwen, professor of pharmacology in Leiden, together with De Lind van Wijngaarden published data on an increase of common colds in the population in general and an increase of symptoms in asthmatic patients during the period August 8-10, 1931. In asthmatics treated in 'climatized rooms' this aggravation was not observed. In this connection the authors refer to the 'allergen-free' nature of these rooms. After studying the meteorological data of August 1931, however, we conclude that the colds and the aggravation of the asthmatic complaints in the period of August 8-10 were probably due to a sudden fall of the temperature from 30 to 15 degrees C in the period August 5-10, owing to a change of weather with influx of cold polar air.

Asthma↗
PubMed1991

Estimation of the allergen content of house dust samples by enzymatic assay.

House dust extracts contain protease and acid phosphatase activities which can be shown to be related to the content of major allergens for humans. A study of the quantitative association between measured enzyme activities and the potency of the extracts to bind IgE antibodies from the serum of house-dust-allergic patients is presented. Since major allergens from mites and other insects contributing to the allergenic potential of household dust on chemical isolation coincide with proteolytic enzymes, and since the bulk of pollen allergenic activity is related to acid phosphatase, the method presented here allows the quantitative appraisal of the contribution of the biomass of animal and plant origin to the allergenic potency of environmental dust samples without the use of human blood samples as sources of specific antibodies.

Acid Phosphatase↗