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P M Rademaker

Publications and source records attributed to P M Rademaker.

18 recordsLinked to original sources
PubMed1991

Induction of active immunological hypo/non-responsiveness to C5 in adult C5-deficient DBA/2 mice.

Injection of C5-sufficient BALB/c serum rendered DBA/2 mice (C5-deficient) immunologically hypo- or non-responsive to C5. This was indicated by C5-elimination studies in the C5-deficient mice showing similar half-lives for C5 upon single and repeated BALB/c serum injection. Concrete evidence for C5 non-responsiveness came from experiments showing that C5-injected DBA/2 mice were unable to mount an anti-C5 antibody response after active immunization with C5-sufficient serum in Freund's complete adjuvant. C5 hypo/non-responsiveness could be induced in DBA/2 mice via the intravenous as well as the intraperitoneal route, provided the C5-sufficient serum was administered in the very narrow dose range of 10-100 microliters (approximately 0.3-3 micrograms of C5). Upon i.v. C5 injection, C5 non-responsiveness was nearly complete on Day 4 and lasted about 3 weeks. Hyporesponsiveness was still present 6 weeks after serum injection. C3-/C5-depleting cobra venom factor reversed tolerization for C5, at least when applied within 48 hr after i.v. C5 injection. Similarity between the acquired C5 hypo/non-responsiveness of DBA/2 mice and the established C5 tolerance of BALB/c mice was suggested by adoptive cell transfer experiments: spleen cells from naive DBA/2 mice stimulated B cells of C5-sufficient nude mice to produce C5-neutralizing antibodies. In contrast, splenocytes from C5-tolerized DBA/2 mice, like those of BALB/c mice, did not decrease haemolytic C5 levels in C5-sufficient nude mice.

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

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

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

Study of the optimal reaction conditions for assay of the mouse alternative complement pathway.

The optimal reaction conditions for hemolytic assay of alternative complement pathway activity in mouse serum were investigated. A microtiter system was used, in which a number of 7.5 X 10(6) rabbit erythrocytes per test well appeared to be optimal. Rabbit erythrocytes were superior as target cells over erythrocytes from a number of other animal species. The optimal conditions were as follows: an incubation temperature of 39 degrees C, an ionic strength of about 200 mM, and a magnesium concentration of 2.5 mM. Incubation during 60 min was not sufficient for an end-point titration. Addition of 1 mg of zymosan A per test well, however, enhanced and accelerated the hemolytic activity of mouse serum via the alternative pathway resulting in a maximum value after 45 min. This, most probably, proceeded by a mechanism involving the formation of a zymosan-C5-convertase and bystander lysis of the target cells. In contrast to the normal alternative pathway assay the zymosan-potentiated test did, most probably, not involve natural antibodies. Cobra venom factor was more efficient in enhancing the sensitivity of the assay for the mouse alternative complement pathway than zymosan. This makes this factor very useful for testing C-poor body fluids.

Animals↗
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↗
PubMed1983

A study of the sensitivity of erythrocytes to lysis by heterologous sera via the alternative complement pathway.

In order to get insight in the distribution of alternative complement pathway activities as detected by lysis of xenogeneic erythrocytes in the presence of magnesium and ethyleneglycol-bis-(2-aminoethyl)-tetra-acetic acid (EGTA) over the species, the 156 heterologous combinations of erythrocytes and sera out of thirteen animal species were tested. An order could be noticed in the species with respect to serum complement activity tending to negative correlation with the sensitivity of the corresponding erythrocytes to lysis by heterologous sera. So far, the most sensitive erythrocyte for each individual serum must be considered to be the target cell of choice for developing assays for alternative complement pathway activity in the serum involved. In this series of animals only for rabbit serum no sensitive target cell was found. The order observed, in connection with the failing lysis of erythrocytes by homologous sera, suggests further that in restriction of heterologous hemolysis in general one erythrocyte-associated, species-nonspecific regulatory principle may be involved, whereas in homologous restriction, most probably, also species-specific factors play a role.

Animals↗
PubMed1983

Effects of immunological adjuvants on the mouse complement system. I. The inability of the polyanion heparin to act as an adjuvant is paralleled by inefficient alternative complement pathway inhibition.

Interference with hemolytic complement activity by polyanionic substances was studied in relation to the ability of these compounds to act as an adjuvant for a dead listeria vaccine. Heparin appeared a poor inhibitor of the mouse alternative pathway not only in contrast to its effects on the mouse classical and the human classical and alternative pathways, but also when compared to two polyanions with known adjuvant activity: dextran sulfate and suramin. For the three polyanions mentioned a correlation between adjuvant activity and mouse alternative pathway inhibition was observed. These findings suggest a possible causal relationship between interference with alternative complement pathway activation and adjuvant activity.

Adjuvants, Immunologic↗
PubMed1983

Antigen-specific helper activity in serum of mice primed with sheep red cells II. Partial purification of the factors involved.

The nature of antigen-specific, T-cell dependent helper activity (SSHA), present in serum of mice 9 h after intraperitoneal immunization with 2 x 10(8) sheep erythrocytes, was studied in more detail. SSHA could be enriched from serum by adsorption to formalinized sheep erythrocytes, elution of the cells with a chaotropic substance, and subsequent dialysis. This resulted in an enrichment of about 900 x with a yield of 64%. Further fractionation of the material by ultrafiltration resulted in two subfractions with helper activity indicating SSHA to be composed of two factors with mol. wt's of greater than 300,000 and about 60,000. The eventual purification for the two factors was about 1650 and 2000 x respectively, and the total yield 46%. The possible relationship between the factors and factors described by others after induction in vitro is discussed. The purification procedure appears useful for the enrichment of SRBC-specific helper factors from serum.

Animals↗
PubMed1981

Involvement of membrane-associated sialic acid in the resistance of sheep erythrocytes to lysis by mouse complement.

The sensitivity of the murine complement system to regulation by membrane-associated sialic acid was investigated. Therefore the C-mediated lysis of sialic acid-rich sheep erythrocytes, sialic acid-poor rabbit erythrocytes and enzymatically desialylated sheep erythrocytes was studied. Mouse complement differed from human and guinea pig complement in that besides the alternative, also the classical pathway appeared sensitive to regulation by surface sialic acid. The possible reaction mechanisms behind the selective sensitivity of the murine classical pathway to membrane-linked sialic acid are discussed and will be subject of further study.

Animals↗
PubMed1981

Interactions of killed Listeria monocytogenes with the mouse complement system.

Incubation of mouse serum with Listeria monocytogenes involved activation of the alternative complement pathway, resulting in depletion of both classical and alternative pathway activity. The activation process gave rise to reactive (calcium- and magnesium-independent) lysis of, specifically, rabbit erythrocytes, which become resistant to this form of hemolysis by sensitization with antibodies. The possible implications of these findings for L. monocytogenes as an intracellular parasite and for rabbit erythrocytes as target cells for mouse alternative complement pathway activity are discussed.

Animals↗
PubMed1980

Estimation of classical pathway of mouse complement activity by use of sensitized rabbit erythrocytes.

A simple photometric assay was devised for determining classical complement pathway activity in mouse serum using sensitized rabbit erythrocytes as target cells. These cells appeared more sensitive to lysis by mouse complement than sensitized mouse and sheep erythrocytes, most probably by their ability to escape the C3b inactivator system. Advantages of the assay over other techniques are the high sensitivity and the avoidance of the use of radioisotopes. With this test it is possible to get more insight in the complement system of an animal species that has been most widely in use in immunological research.

Animals↗
PubMed1980

Determination of alternative pathway of complement activity in mouse serum using rabbit erythrocytes.

Rabbit, mouse and sheep erythrocytes expressing different concentrations of membrane sialic acid were used to study possible modes of activation of the alternative complement (C) pathway in mouse, human and guinea pig serum. Mouse erythrocytes activated only human serum, whereas rabbit erythrocytes activated the sera of all three species. Based on the observation that rabbit erythrocytes activate the murine alternative C pathway a method for estimation of alternative C pathway activity (AP50 value) in mouse serum was devised analogous to that used for human AP50 determination. The method is not very sensitive to ageing or to batch variation of the indicator cells. The AP50 value of mouse serum measured by this method is of the same order as for human and guinea pig serum. Mouse serum AP50 activity is partly determined by natural anti-rabbit erythrocyte antibodies and is sensitive to heating (15' at 48 degrees C and 4' at 56 degrees C), and to the actions of cobra venom factor, zymosan and cysteine. Strain and sex differences with respect to AP50 activities of mouse sera were observed.

Animals↗
PubMed1980

Histamine 2-receptor-mediated immunomodulation in the mouse. II. Immunomodulation by the H2 antagonist metiamide.

Modulation of delayed hypersensitivity and antibody formation to sheep red cells by metiamide were studied in the mouse system. Depending on the time and dose of antigen and metiamide administration suppression or enhancement of the delayed hypersensitivity response was observed. The effects in this system did not differ from those reported for the H2 agonist tolazoline, which were most probably mediated by suppressor cells. As far as the humoral response was concerned metiamide tended to stimulate the IgM response. Optimal stimulation was reached if 50 mg metiamide/kg was administered 3 days before immunization with 2 x 10(8) SRBC. Under all conditions tested the IgG response was unaffected. These results suggest antagonistic effects of metiamide for tolazoline and adduce further evidence for the presence of H2 receptors on B cells. The IgM production per plasmacell was enhanced suggesting different H2 receptors to be involved in differentiative and proliferative B cell responses. The possible consequences of H2 antagonist application in human therapy are discussed.

Animals↗
PubMed1979

Differential potencies of corticosterone and hydrocortisone in immune and immune-related processes in the mouse.

The effects of corticosterone and hydrocortisone on the thymus, the pituitary--adrenal axis, delayed hypersensitivity, the corticosterone plasma level and the numbers of circulating nucleated and monocytic cells were investigated in the mouse. Short-term effects within 48 h after one or two corticoid injections and late effects 7 days after a regimen of 4 corticoid injections were discerned. In short-term experiments hydrocortisone was more active than corticosterone upon the induction of leukopenia and monocytopenia and the inhibition of delayed hypersensitivity. However, regarding late effects and the short-term effect on adrenal weight, corticosterone far exceeded hydrocortisone in activity. Our results could be explained by assuming two feedback-inhibition systems for glycocorticoids. The first, likely to be responsible for the changes observed for the adrenal weight and the numbers of ciruclating white cells after a single glucocorticoid injection, was shown to be expressed in a soluble factor released in the blood stream tentatively designated "glucocorticoid inhibiting factor. The factor was more readily induced by hydrocortisone but displayed a greater specificity in inhibiting effects of corticosterone. The second feedback-inhibition system, responsible for increased numbers of circulating monocytes paralleled by an enhanced delayed hypersensitivity response, was expressed in a decreased corticosterone plasma level, most probably secondary to a diminished release of ACTH from the pituitary gland. With the glucocorticoid doses we used the second feedback-inhibition system was only triggered by the more physiological hormone, corticosterone.

Adrenal Glands↗