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Biomedical subjects

H van Dijk

Publications and source records attributed to H van Dijk.

At least 73 records · Page 4Linked to original sources
PubMed1989

Characterization of anti-complement compounds from Azadirachta indica.

The crude aqueous extract of Azadirachta indica bark possesses an inhibitory activity on both classical (CP) and alternative pathway (AP) activation of human complement. Purification of the compounds with the guidance of the AP-inhibitory activity involved extraction with methanol, dialysis, ion-exchange procedures and gel-permeation chromatography. This sequence yielded two polymers, NB-I and NB-II, one a highly active compound with a relatively low molecular weight (NB-II) and the other a less active compound with a high molecular weight (NB-I). The polymers were characterized by using colour reactions, TLC, GLC and HPLC after hydrolysis and gel-permeation chromatography as peptidoglycans. The carbohydrate part consisted predominantly of glucose. Arabinose, galactose and mannose were present in minor amounts (NB-II) or only as traces (NB-I). Protein was present for 5.5% in NB-I and for 9.8% in NB-II.

Chemical Phenomena↗
PubMed1989

Inhibitory activity of Jatropha multifida latex on classical complement pathway activity in human serum mediated by a calcium-binding proanthocyanidin.

This study isolates and characterizes the anti-complement constituent(s) present in the latex of Jatropha multifida, in an attempt to explain the traditional application of the latex in the treatment of infected wounds. Guided by the inhibition of classical pathway (CP) complement activity in human serum, a polymer was isolated which could be characterized as a proanthocyanidin. The polymer inhibits CP activation of the complement cascade, while alternative pathway (AP) activation is relatively insensitive to the polymer. This is due to the selective depletion of Ca2+, but not Mg2+, from the incubation medium.

Anthocyanins↗
PubMed1989

An anti-complementary polysaccharide with immunological adjuvant activity from the leaf parenchyma gel of Aloe vera.

The aim of the study is to develop new substances with immunomodulatory activity. To this end, extracts from plants used in traditional medicine are used as starting material. This study deals with the mucilagenous leaf-gel of Aloe vera which is well reputed for its therapeutical effect on inflammatory-based disorders. The purification of an aqueous gel-extract guided by inhibition of complement activity in HPS is described. Using anion-exchange and gel permeation chromatography a highly active polysaccharide fraction was isolated, that is present in the gel in various chain lengths. The polysaccharides consist of several monosaccharides of which mannose is dominant. The inhibition is based on alternative pathway activation, resulting in consumption of C3. With respect to their biological activity the polysaccharides inhibit the opsonization of zymosan in HPS and display adjuvant activity on specific antibody production and the induction of delayed type hypersensitivity in mice.

Adjuvants, Immunologic↗
PubMed1989

Relation between splenic antibody formation and serum antibody levels to sheep erythrocytes as studied at the level of individual mice.

The relation between splenic antibody formation and serum antibody levels after intraperitoneal immunization of mice with sheep erythrocytes was studied in individual animals. A strong correlation between plaque-forming cell numbers in the spleen and haemolysin and haemagglutinin titres in the serum was observed. These results are at variance with recent data on the development of splenic auto-haemolysin-forming cells and corresponding serum levels after injection of mice with Escherichia coli endotoxin. The background behind the discrepancy between the antigen-driven immune response and the more polyclonal stimulation of B cells with endotoxin is being discussed.

Animals↗
PubMed1988

Evidence that superoxide-anion, produced by PMA-activated human polymorphonuclear leukocytes, is the cytolytic agent for rabbit, but not for sheep red blood cells.

The lysis of sheep and rabbit red blood cells (SRBC and RRBC, respectively) upon exposure to PMA-activated human polymorphonuclear leukocytes (PMN) was investigated. The lysis of these target cells, which was measured by the release of 51Cr, showed different kinetics and scavenger-sensitivity. The lysis of RRBC, which was already detectable within 45 min of incubation, was sensitive to superoxide dismutase (SOD), but was only poorly influenced by scavengers of hydroxyl radical formation, such as desferal or thiourea. In contrast, lysis of SRBC was first detectable after 90 to 135 min of incubation and sensitive to desferal and thiourea, but not to SOD. Finally, only RRBC were sensitive to the artificial superoxide-generating system hypoxanthine/xanthine oxidase. Taken together, these data point at a cytolytic activity of superoxide anion O2- towards RRBC. SRBC are relatively resistant to O2-, but are lysed by an H2O2- and hydroxyl radical-dependent process.

Animals↗
PubMed1988

Rabbit antisera to enterobacteriaceae isolated from HLA-B27 positive patients with ankylosing spondylitis (AS) are lytic for the mononuclear cells of AS patients.

Vaccines prepared from Gram-negative bacteria isolated from the stools of HLA-B27 positive AS patients were used to immunize rabbits. Three of the sera obtained were lytic in vitro for the mononuclear cells of HLA-B27 positive AS patients. One of these sera discriminated between AS patients and healthy HLA-B27 positive individuals. Cytolysis was determined in an automated, non-radioactive assay based on the release of carboxyfluorescein diacetate and the incorporation of propidium iodide.

Animals↗
PubMed1988

Endotoxin-induced auto-immunity in mice. II. Reactivity of LPS-hyporesponsive and C5-deficient animals.

Auto-antibody responses and circulating immune complex levels of mice with abnormal reactions to endotoxin were investigated after injection with the bacterial product. It was observed that C3H/HeJ mice displayed very high background plaque-forming cell responses towards bromelain-treated isologous erythrocytes which were slightly enhanced by endotoxin treatment. The same animals, however, did not bear autohaemolysins in their serum, but became so upon endotoxin injection. A possible relationship between the high background reactivity of C3H/HeJ mice and the low toxicity of endotoxin in these animals is discussed. Neither untreated nor lipopolysaccharide-injected C3H/HeJ mice showed significant immune complex levels in their sera. This may be explained by their hyporesponsiveness, but by a low sensitivity to the toxic effects of endotoxin as well. C5-deficient and C5-sufficient mice showed similar auto-immune reactions, indicating that C5a, which is responsible for other effects of endotoxin, is not involved in endotoxin-induced auto-immunity.

Animals↗
PubMed1987

House dust extracts contain potent immunological adjuvants.

A crude aqueous extract of house dust and two house dust subfractions were tested for adjuvant activity in a sensitivity assay performed in mice. Evidence is presented that house dust contains at least two potent immunological adjuvants. One of these, present in both subfractions, was probably endotoxin and acted in a complement-independent way. The immunostimulatory effect of the other adjuvant was abrogated by prior complement depletion of the animals. This apparently complement-dependent adjuvant needs further identification.

Adjuvants, Immunologic↗
PubMed1987

Endotoxin-induced auto-immunity in mice. I. Time and dose dependence of production and serum levels of antibodies against bromelain-treated mouse erythrocytes and circulating immune complexes.

Injection of mice with endotoxin results in the formation of auto-antibodies and the appearance of soluble immune complexes in the blood. In this study the relationship between the production and serum levels of autohaemolysins and circulating immune complex titres was investigated. Immune complexes were detected by a solid-phase C1q-binding assay and found to contain antibodies of the IgM, but not of the IgG class. Individual mice showed marked differences as to their splenic plaque-forming cells, serum autohaemolysin, and circulating immune complex responses, both in kinetic studies and dose-response experiments. The dissociation between production and serum levels of auto-antibodies was ascribed to extrasplenic synthesis or a disproportionate production per plasma cell. The independent behaviour of the circulating immune complex response could, at least partially, be attributed to differential complement-dependent clearance from the circulation. The implications of our findings for the laboratory diagnosis of auto-immunity at the blood level are being discussed.

Animals↗
PubMed1986

Study on the pre-haemolytic complex formed upon polyethylene glycol-induced activation of mouse complement.

The stability and nature of haemolytic activity generated in normal mouse serum upon precipitation with a critical amount of polyethylene glycol and incubation of the redissolved precipitate in the presence of 10 mM EDTA were investigated. The activity appeared to be stable at 0 degrees C which enabled further analysis. The haemolytic mixture was subfractionated by repeated differential polyethylene glycol precipitation yielding two preparations with little or no haemolytic activity by themselves, but which regained activity upon recombination. Material precipitating between 4 and 9% polyethylene glycol became haemolytic when combined with C5-deficient serum. The ultracentrifugation profile of this subfraction strongly suggested the presence of C56-complexes.

Animals↗
PubMed1986

EDTA-resistant activation of the terminal route of mouse complement after partial precipitation of serum with polyethylene glycol.

A new type of activation of the terminal route of complement is described. It occurs in precipitates of mouse serum prepared with a critical amount of polyethylene glycol. The activation proceeds in the presence of 10 mM EDTA and in the absence of C1q and functional C2, C3, C4 and factor B, which suggests that it is classical and alternative pathway-independent. The activation is demonstrated by the generation of both thermo-labile haemolytic and thermo-stable chemotactic activity. For both activities C5 seems to be essential. The haemolytic activity does not show species restriction towards sheep erythrocytes, which suggests a similarity with C56-initiated (reactive) but not with (S)C5-9-mediated (deviated) haemolysis. The identity of the haemolytic complex and the chemoattractant and the possible use of the new activation for the functional analysis of the mouse terminal complement route will be the subject of further study.

Animals↗
PubMed1986

House dust allergen activates the classical complement pathway in mouse serum.

A house dust fraction was tested for complement activation in mouse serum using a microtitre complement fixation assay. It was observed that the preparation was a potent activator of the classical, but not of the alternative pathway suggesting an analogy with the complement activation in human serum. The activation showed similarity with that by classical complement activators such as aggregated IgG, DNA, lipopolysaccharide (LPS), but some discrepancy with mite allergen was observed. The contamination of the preparation with LPS was negligible and could not account for the anticomplementary effect. The role of DNA fragments in the activation of mouse complement by the house dust fraction is discussed. Our results suggest that the mouse is suited to study the role of complement activation by house dust constituents in the induction of the IgE response.

Allergens↗
PubMed1986

Suppression of migration inhibition factor (MIF) production by mitomycins in vitro.

The effects of a series of mitomycins in a modified version of the Migration Inhibition Factor (MIF) test were investigated. This modified assay, which uses monocytes of the mouse cell line WEHI3 as target cells for MIF, discriminates between effects on the migrating monocytes, the production of MIF by lymphocytes and the activity of the produced MIF. The 7-methoxy mitomycins were found to be more active than the 7-amino and 7-hydroxy derivatives in suppressing both the spontaneous migration of target monocytes and the MIF production by lymphocytes. Neither of the compounds had a significant effect on the activity of produced MIF. A relationship between the activities of the mitomycins and their lipophilicity and polarographic half-wave potential is discussed. Further attention is paid to the stability of the mitomycins under the test conditions and additional advantages of the modified MIF assay over related in vitro tests for cell-mediated immunity.

Animals↗
PubMed1986

Complement split product C5a mediates the lipopolysaccharide-induced mobilization of CFU-s and haemopoietic progenitor cells, but not the mobilization induced by proteolytic enzymes.

Intravenous (i.v.) injection of mice with lipopolysaccharide (LPS), and the proteolytic enzymes trypsin and proteinase, mobilizes pluripotent haemopoietic stem cells (CFU-s) as well as granulocyte-macrophage progenitor cells (GM-CFU) and the early progenitors of the erythroid lineage (E-BFU) from the haemopoietic tissues into the peripheral blood. We investigated the involvement of the complement (C) system in this process. It appeared that the early mobilization induced by LPS and other activators of the alternative complement pathway, such as Listeria monocytogenes (Lm) and zymosan, but not that induced by the proteolytic enzymes, was absent in C5-deficient mice. The mobilization by C activators in these mice could be restored by injection of C5-sufficient serum, suggesting a critical role for C5. The manner in which C5 was involved in the C activation-mediated stem cell mobilization was studied using a serum transfer system. C5-sufficient serum, activated in vitro by incubation with Lm and subsequently liberated from the bacteria, caused mobilization in both C5-sufficient and C5-deficient mice. C5-deficient serum was not able to do so. The resistance of the mobilizing principle to heat treatment (56 degrees C, 30 min) strongly suggests that it is identical with the C5 split product C5a, or an in vivo derivative of C5a. This conclusion was reinforced by the observation that a single injection of purified rat C5a into C5-deficient mice also induced mobilization of CFU-s.

Animals↗
PubMed1986

A new, sensitive assay to determine immunological adjuvant activity based on the immunogenicity of neuraminidase-treated sheep erythrocytes.

A novel, sensitive system to determine immunological adjuvant activity is presented. It is based on the direct haemagglutinin response of mice to neuraminidase-treated sheep red blood cells (asialo-SRBC) seven days after i.p. immunization. For two model adjuvants it is shown that the response is more sensitive to stimulation than that to normal SRBC. Optimal stimulatory activity was measured at an antigen dose of 3 x 10(6) asialo-SRBC. Using this dose stimulation indices up to 100 were observed. The minimal effective dose of dextran sulphate, the so far most potent adjuvant in the model, was only 1 microgram. It is further shown that, in addition to substances with a rather general immunostimulatory activity, compounds with adjuvanticity which is commonly restricted to cellular responses are also effective in the system. The latter and reduced activity of the model adjuvants in nude mice strongly suggest that adjuvanticity in the asialo-SRBC model is T cell-dependent. Suppression of adjuvant activity in cobra venom factor-pretreated animals may indicate an involvement of complement in extrinsic immunostimulatory activity. Results show that the asialo-SRBC model is very suitable for evaluation and mechanistic study of immunological adjuvant activity.

Adjuvants, Immunologic↗
PubMed1985

Anti-complementary amines are immunological adjuvants in mice.

Complement (C) inactivation by ammonia, ethylenediamine and methylamine in mouse serum was studied in relation to a possible adjuvant effect of the substances in a cell-mediated immune response. The amines caused a dose-dependent depletion of both alternative pathway (AP) and overall C activity in vitro and showed also pronounced adjuvant effects in the delayed type hypersensitivity response of mice to SRBC. A significant correlation between momentary inhibition of AP activity and adjuvanticity was observed (r = 0.9995; P approximately 0.02), suggesting a causative relationship between these two phenomena. Both effects seem to be a direct function of the number of amino-groups per molecule. Since, on the other hand, lysosomotropic activity of amines is known to decrease with the number of amino-residues, our findings exclude an important role of direct phagocyte inhibition in the immuno-adjuvanticity of these compounds. A longer persistence and improved presentation of antigen as indirect result of local C-depletion could account for the immunological adjuvant effects of amines.

Adjuvants, Immunologic↗
PubMed1985

Surface-associated sialic acid is an immunological adjuvant.

The influence of neuraminidase on the immunogenicity of heterologous erythrocytes as determined by serum haemagglutination titres was investigated in mice. For this study sheep and rabbit erythrocytes were selected because of their high and low N-acetylneuraminic (sialic) acid content, respectively. Preincubation with neuraminidase resulted in a ten-fold reduction of the immunogenicity of sheep erythrocytes (ShE). By contrast, the immune response to rabbit erythrocytes appeared to be resistant to sialidase treatment. Addition of the extrinsic adjuvant dimethyldioctadecylammonium bromide largely restored the immunogenicity of neuraminidase-treated ShE, but did not change the response to control-treated ShE. The maximal antibody level induced by neuraminidase-treated ShE was lower than that provoked by control ShE. These results suggest that sialic acid is both an intrinsic immunological adjuvant and an antigenic determinant of ShE. The adjuvant effect of sialic acid does not depend on complement component C3 as judged by the response of cobra venom factor-pretreated animals. In genetically C5-deficient and in nude mice, however, sialic acid showed diminished and absent adjuvant activity, respectively.

Adjuvants, Immunologic↗